During the manufacture of pharmaceuticals, <a target="_blank" rel="noopener noreferrer" href="https://gcms.labrulez.com/library?mainauthorItems=45&amp;search=1%2C+4-Dioxane">1, 4-Dioxane</a> is used as a cleansing agent. It is also a byproduct of plastic manufacturing. The most likely exposure to 1, 4-Dioxane is at an industrial site. However, if any 1, 4-Dioxane is released into the environment during manufacturing there is a potential for it to migrate into ground water. The fact that 1, 4-Dioxane is so miscible in water makes degradation of the chemical challenging. Ethanol, on the other hand, has been a popular gasoline additive. Since it burns more quickly and completely than gasoline, emissions from car exhaust are decreased. The downside of this is underground storage tank leakage and fuel spills cause ground water and drinking water to be contaminated with both the fuel and the ethanol additive. Since ethanol is also very miscible in water, the detection of ethanol contamination in water can be difficult.&nbsp;There have been several innovations that help overcome the obstacles of detecting 1, 4-Dioxane and Ethanol. The first one is the SIM mode of the mass spectrometer. This mode allows better detection of hard to extract compounds. Furthermore, mass spectrometers are now equipped to run SIM/Scan, this not only helps detect more difficult compounds, but also enables the detection of an extensive list of <a target="_blank" rel="noopener noreferrer" href="https://gcms.labrulez.com/library?mainauthorItems=45&amp;search=USEPA+Method+8260">USEPA Method 8260</a> compounds without having to run the samples twice. Advancements in purge and trap sampling have also facilitated better detection of these compounds. Most effective in this has been the ability to heat the samples. However, there are drawbacks to better detection. The most problematic of these is the tendency of 1, 4-Dioxane and Ethanol to “stick” to the glass ware. This susceptibility has caused many headaches in environmental labs.&nbsp;This application note will investigate seven variations of <a target="_blank" rel="noopener noreferrer" href="https://gcms.labrulez.com/library?mainauthorItems=45&amp;search=purge+and+trap">purge and trap</a> sampling. The data will then be evaluated in order to recommend the optimum purge and trap sampling parameters for your lab.<h4>Experimental:&nbsp;</h4>The sampling system used for this study was the <a target="_blank" rel="noopener noreferrer" href="https://gcms.labrulez.com/products/2160">EST Analytical Evolution concentrator</a> affixed with a Vocarb 3000 trap. The <a target="_blank" rel="noopener noreferrer" href="https://gcms.labrulez.com/products/2159">Centurion WS autosampler</a> equipped with the syringe option was employed as the autosampler. The separation and analysis were performed by an <a target="_blank" rel="noopener noreferrer" href="https://gcms.labrulez.com/library?mainauthorItems=10&amp;search=7890A+Gas+Chromatograph">Agilent 7890A Gas Chromatograph (GC)</a> and <a target="_blank" rel="noopener noreferrer" href="https://gcms.labrulez.com/library?mainauthorItems=10&amp;search=5975C+Mass+Spectrometer">5975C inert XL Mass Spectrometer (MS).</a> The GC was configured with a <a target="_blank" rel="noopener noreferrer" href="https://gcms.labrulez.com/library?mainauthorItems=7&amp;search=Rxi-624+Sil+MS">Restek Rxi-624 Sil MS</a> 30m x 0.25mm x 1.4µm column. The purge and trap and GC/MS parameters used for this study are listed below.<h5>Purge and Trap Parameters</h5><ul><li>Concentrator: EST Encon Evolution</li><li>Trap type: Vocarb 3000</li><li>Valve oven temperature: 150 °C</li><li>Transfer line temperature: 150 °C</li><li>Trap temperature: 35 °C</li><li>Moisture Reduction Trap (MoRT) temperature: 39 °C</li><li>Purge time: 11 min</li><li>Purge flow: 40 mL/min</li><li>Dry purge: Ambient temperature, 40 mL/min, 1.0 min</li><li>Desorb pressure: 5 psi (with control ON)</li><li>Desorb time: 0.5 min</li><li>Desorb preheat delay: 10 sec</li><li>Desorb temperature: 250 °C</li><li>MoRT bake temperature: 210 °C</li><li>Bake temperature: 260 °C</li><li>Sparge vessel bake temperature: 40 °C for 3 min, ramp to 100–110 °C, hold</li><li>Bake time: 6 min</li><li>Bake flow: 85 mL/min</li></ul><h5>Auto-Sampler (EST Centurion WS):</h5><ul><li>Sample type: Water</li><li>Sample volume: 5 or 10 mL</li><li>Internal standard volume: 5 µL</li></ul><h5>GC/MS Parameters</h5><ul><li>System: Agilent 7890A GC / 5975C inert XL MS</li><li>Inlet: Split mode, 220 °C, 40:1 split ratio, 12.153 psi head pressure</li><li>Column: Restek Rxi-624Sil MS, 30 m × 0.25 mm × 1.4 µm</li><li>Oven program: 45 °C (1 min) → ramp 15 °C/min → 220 °C, hold 1.33 min (total run ~14 min)</li><li>Column flow rate: 1 mL/min helium</li><li>Total flow: 44 mL/min</li><li>Source temperature: 230 °C</li><li>Quadrupole temperature: 150 °C</li><li>Transfer line temperature: 180 °C</li><li>Scan range: m/z 35–300, 5.2 scans/sec</li><li>SIM ions:<ul><li>45, 46 (0.7–3.49 min)</li><li>58, 88 (3.5–14 min)</li></ul></li><li>Solvent delay: 0.7 min</li></ul>For each parameter iteration, see the text below, a calibration curve was established with a linear range of 0.5 to 200ppb using standards from Restek. After each of the prescribed curves was determined; Method Detection Limits (MDLs), precision and accuracy and carryover studies were performed. A series of seven low level standards were run in order to establish MDLs per 40CFR Part 136, Appendix B. Next, seven replicate samples of the 50ppb standard were run in order to establish the precision and the accuracy of the experimental parameters. Finally, a series of four 50ppb standards were run with each standard followed by three blanks. The amount of carryover was then analyzed in the first blank. The data from each parameter variation was compiled and compared in order to determine the optimum conditions for this analysis. An average of the results for each analysis condition is listed in Table 1.<h5>Purge and Trap Sampling Test Parameters</h5><ul><li>Baseline: 5 mL traditional sparger, room temp purge, 110 °C sparge bake</li><li>Iteration A: 5 mL traditional sparger, 40 °C purge, 110 °C sparge bake</li><li>Iteration B: 5 mL traditional sparger, 60 °C purge, 110 °C sparge bake</li><li>Iteration C: 5 mL traditional sparger, 40 °C purge, no sparge bake</li><li>Iteration D: 40 mL vial, 10 mL purge volume, 40 °C purge, no sparge bake</li><li>Iteration E: 5 mL fritless bulbless sparger, 40 °C purge, 110 °C sparge bake</li><li>Iteration F: 5 mL fritless bulbless sparger, 40 °C purge, no sparge bake (Iteration E used the patented Water/Soil prep mode)</li></ul><img src="https://storage.googleapis.com/labrulez-bucket-strapi-h3hsga3/EST_Analytical_Table_4_Averaged_Results_Summary_306dcbfde6.jpg" alt="EST Analytical: Table 1 Averaged Results Summary" srcset="https://storage.googleapis.com/labrulez-bucket-strapi-h3hsga3/thumbnail_EST_Analytical_Table_4_Averaged_Results_Summary_306dcbfde6.jpg 245w," sizes="100vw" width="1493" height="351">The primary compounds of interest for the study were Ethanol and 1, 4-Dioxane. For this reason, the data for these compounds was compiled separately in order to better distinguish the benefits or detriment of each purge and trap parameter set. The experimental results of the precision and percent recovery studies are displayed in Tables 2 and 3.<img src="https://storage.googleapis.com/labrulez-bucket-strapi-h3hsga3/EST_Analytical_Table_5_Ethanol_and_1_4_Dioxane_Precision_at_50ppb_3a195e1acb.jpg" alt="EST Analytical: Table 2 Ethanol and 1, 4-Dioxane Precision at 50ppb" srcset="https://storage.googleapis.com/labrulez-bucket-strapi-h3hsga3/thumbnail_EST_Analytical_Table_5_Ethanol_and_1_4_Dioxane_Precision_at_50ppb_3a195e1acb.jpg 245w," sizes="100vw" width="1316" height="236"><img src="https://storage.googleapis.com/labrulez-bucket-strapi-h3hsga3/EST_Analytical_Table_6_Ethanol_and_1_4_Dioxane_Percent_Recovery_at_50ppb_cb12616f47.jpg" alt="EST Analytical: Table 3 Ethanol and 1, 4-Dioxane Percent Recovery at 50ppb" srcset="https://storage.googleapis.com/labrulez-bucket-strapi-h3hsga3/thumbnail_EST_Analytical_Table_6_Ethanol_and_1_4_Dioxane_Percent_Recovery_at_50ppb_cb12616f47.jpg 245w," sizes="100vw" width="1318" height="234">For the carryover studies, Ethanol and 1, 4-Dioxane were examined along with the carryover of 1, 2, 4- Trichlorobenzene, Naphthalene and 1, 2, 3-Trichlorobenzene. The reason the heavier compounds were included in this study was a concern that changing the sampling parameters may help the Ethanol and 1, 4-Dioxane carryover, but harm the carryover of the heavier compounds of interest. Table 4 shows a listing of the carryover results, in parts per billion, while Figure 1 displays the percent carryover of the different purge and trap experimental parameters for just the Ethanol and 1, 4-Dioxane.<img src="https://storage.googleapis.com/labrulez-bucket-strapi-h3hsga3/EST_Analytical_Table_7_Carryover_in_First_Blank_after_a_50ppb_Standard_7d2bc81626.jpg" alt="EST Analytical: Table 4 Carryover in First Blank after a 50ppb Standard" srcset="https://storage.googleapis.com/labrulez-bucket-strapi-h3hsga3/thumbnail_EST_Analytical_Table_7_Carryover_in_First_Blank_after_a_50ppb_Standard_7d2bc81626.jpg 245w," sizes="100vw" width="1332" height="426"><img src="https://storage.googleapis.com/labrulez-bucket-strapi-h3hsga3/EST_Analytical_Figure_1_Ethanol_and_1_4_Dioxane_Percent_Carryover_after_a_50ppb_Standard_Graphic_f57c981913.jpg" alt="EST Analytical: Figure 1 Ethanol and 1, 4-Dioxane Percent Carryover after a 50ppb Standard Graphic" srcset="https://storage.googleapis.com/labrulez-bucket-strapi-h3hsga3/thumbnail_EST_Analytical_Figure_1_Ethanol_and_1_4_Dioxane_Percent_Carryover_after_a_50ppb_Standard_Graphic_f57c981913.jpg 245w," sizes="100vw" width="1358" height="787">After all the studies were completed, two purge and trap parameter variations showed the best precision, percent recovery, and carryover while meeting the USEPA Method 8260 linearity and response factor requirements. An abbreviated listing of the results for these two iterations are shown in Table 5.<img src="https://storage.googleapis.com/labrulez-bucket-strapi-h3hsga3/EST_Analytical_Table_8_Results_of_the_Water_Extraction_and_the_Fritless_Bulbless_Sparge_Vessel_With_Sparge_Bake_Studies_9b71ec4951.jpg" alt="EST Analytical: Table 5 Results of the Water Extraction and the Fritless - Bulbless Sparge Vessel With Sparge Bake Studies" srcset="https://storage.googleapis.com/labrulez-bucket-strapi-h3hsga3/thumbnail_EST_Analytical_Table_8_Results_of_the_Water_Extraction_and_the_Fritless_Bulbless_Sparge_Vessel_With_Sparge_Bake_Studies_9b71ec4951.jpg 161w," sizes="100vw" width="1256" height="1221"><h4>Conclusions:&nbsp;</h4>All seven purge and trap parameter iterations passed the USEPA Method 8260 requirements for linearity and method detection limits. The problem with some of the experimental parameters was found in the carryover and precision and accuracy studies. The carryover using the traditional sparge vessel showed a large amount of carryover for the Ethanol and 1, 4-Dioxane. Since the carryover was so high, the precision and accuracy data suffered. The Fritless/Bulbless sparge vessel, on the other hand, displayed much lower carryover for the Ethanol and 1, 4-Dioxane especially when the patented sparge bake was not used. However, the 1, 2, 4-Trichlorobenzene, Naphthalene and 1, 2, 3-Trichlorobenzene carryover after the 50ppb standard was above the lower limit of the curve.&nbsp;Thus, the sparge bake would be recommended in order to limit the carryover of the heavier compounds. The optimum purge and trap parameters proved to be the patented water extraction technique. This technique provided linearity and method detection limits that met the USEPA Method 8260 requirements, while providing excellent precision and accuracy data. During water extraction, the sample is transferred to an empty 40ml vial and then purged in the soil station of the Centurion. The “fresh” vial provides a clean sparge vessel for every sample thus limiting carryover for both the Ethanol and 1, 4-Dioxane and for the heavy compounds. This lack of carryover aided in providing optimum precision and accuracy and carryover results and would be the recommended method for examining these troublesome compounds.

Optimization of 1,4-Dioxane and Ethanol Detection Using USEPA Method 8260

<a target="_blank" rel="noopener noreferrer" href="https://gcms.labrulez.com/library?mainauthorItems=45&amp;search=USEPA+Method+524.2">USEPA Method 524.2</a> calls for purge and trap sampling coupled with a Gas Chromatograph (GC) and Mass Spectrometer (MS) for separation and analysis. It has an extensive list of compounds and requires lower detection limits due to its use in drinking water testing. A 20% relative standard deviation for compound response factors is required across the calibration curve while the calibration check standard analytes have to be within 30% of the expected concentration. Currently, this method calls for a 5mL or 25mL purge volume and a four minute desorb time. These method requirements can pose a challenge for the analyst due to the amount of moisture that is created.&nbsp;The negative effects of the increased water vapor include instability of the chromatography, band eluting and poor peak shape to name a few. A side effect of this instability is sample re-runs and lost laboratory productivity. In addition, a common practice for mitigating moisture is increasing the GC inlet split rate. This poses yet another difficulty as the increased split rate can result in reduced sensitivity. EST Analytical’s eight port valve in the Evolution purge and trap concentrator aids in limiting the water exposure because the water management of the system is not part of the desorb pathway. This feature also enables laboratories to use a smaller split ratio at the GC inlet thus increasing sensitivity.<h4>Experimental:&nbsp;</h4>The sampling system used for this study was the <a target="_blank" rel="noopener noreferrer" href="https://gcms.labrulez.com/products/2160">EST Analytical Evolution purge and trap concentrator</a> and the <a target="_blank" rel="noopener noreferrer" href="https://gcms.labrulez.com/products/2159">Centurion WS autosampler</a>. The concentrator was affixed with a Vocarb 3000 trap and connected to an <a target="_blank" rel="noopener noreferrer" href="https://gcms.labrulez.com/library?mainauthorItems=10&amp;search=7890A">Agilent 7890A GC</a> and <a target="_blank" rel="noopener noreferrer" href="https://gcms.labrulez.com/library?mainauthorItems=10&amp;search=5975C">5975C inert XL MS</a>. The GC was configured with a <a target="_blank" rel="noopener noreferrer" href="https://gcms.labrulez.com/library?mainauthorItems=7&amp;search=Restek+Rxi-624+Sil+MS">Restek Rxi-624 Sil MS</a> 30m x 0.25mm x 1.4µm column. The purge and trap and GC/MS parameters used for this study are listed below.<h5>Purge and Trap Parameters</h5><ul><li>Concentrator: EST Evolution</li><li>Trap type: Vocarb 3000</li><li>Valve oven temperature: 130 °C</li><li>Transfer line temperature: 130 °C</li><li>Trap temperature: 35 °C</li><li>Moisture Reduction Trap (MoRT) temperature: 39 °C</li><li>Purge time: 11 min</li><li>Purge flow: 40 mL/min</li><li>Dry purge Temp.: Ambient</li><li>Dry Purge Flow: 40mL/min</li><li>Dry Purge Time: 1.0 min &nbsp;</li><li>Desorb pressure Control: ON</li><li>Desorb Pressure: 5psi</li><li>Desorb time: 4 min</li><li>Desorb preheat delay: 15 sec</li><li>Desorb temperature: 250 °C</li><li>MoRT bake temperature: 210 °C</li><li>Bake temperature: 260 °C</li><li>Sparge vessel bake temperature: 110 °C</li><li>Bake time: 6 min</li><li>Bake flow: 70 mL/min</li></ul><h5>Auto-Sampler (EST Centurion WS):</h5><ul><li>Sample type: Water</li><li>Water volume: 25 mL</li><li>Internal standard volume: 5 µL</li></ul><h5>GC/MS Parameters</h5><ul><li>System: Agilent 7890A GC / 5975C inert XL MS</li><li>Inlet: Split mode, 220 °C, 40:1 split ratio, 12.153 psi head pressure</li><li>Column: Restek Rxi-624Sil MS, 30 m × 0.25 mm × 1.4 µm</li><li>Oven program: 45 °C (1 min) → ramp 15 °C/min → 220 °C, hold 1.33 min (total run ~14 min)</li><li>Column flow rate: 1 mL/min helium</li><li>Total flow: 44 mL/min</li><li>Source temperature: 230 °C</li><li>Quadrupole temperature: 150 °C</li><li>Transfer line temperature: 180 °C</li><li>Scan range: m/z 35–300, 5.2 scans/sec</li><li>Solvent delay: 0.7 min</li></ul>A calibration curve was established with a linear range of 0.25 to 40µg/L using the USEPA Method 524.2 standards from Restek. After the curve was determined, method detection limits were ascertained by running a series of seven replicate 0.25 µg/L standards and calculated using the procedure outlined in 40 CFR Part 136 Appendix B. Finally, seven 20 µg/L standards were examined in order to verify the precision and accuracy of the analysis. The results of this study are displayed in Tables 1 and 2 while Figure 1 presents a 20 µg/L standard GC/MS chromatogram.<img src="https://storage.googleapis.com/labrulez-bucket-strapi-h3hsga3/EST_Analytical_Table_3_Compound_Linearity_and_Response_Factor_Table_f63b77844f.jpg" alt="EST Analytical: Table 1 - Compound Linearity and Response Factor Table" srcset="https://storage.googleapis.com/labrulez-bucket-strapi-h3hsga3/thumbnail_EST_Analytical_Table_3_Compound_Linearity_and_Response_Factor_Table_f63b77844f.jpg 153w," sizes="100vw" width="1104" height="1126"><img src="https://storage.googleapis.com/labrulez-bucket-strapi-h3hsga3/EST_Analytical_Table_4_MDL_and_Precision_and_Percent_Recovery_Table_27572600f0.jpg" alt="EST Analytical: Table 2 - MDL and Precision and Percent Recovery Table" srcset="https://storage.googleapis.com/labrulez-bucket-strapi-h3hsga3/thumbnail_EST_Analytical_Table_4_MDL_and_Precision_and_Percent_Recovery_Table_27572600f0.jpg 186w," sizes="100vw" width="1358" height="1143"><img src="https://storage.googleapis.com/labrulez-bucket-strapi-h3hsga3/EST_Analytical_Figure_1_20mg_L_Standard_Chromatogram_7ff795984b.jpg" alt="EST Analytical: Figure 1 - 20 µg/L Standard Chromatogram" srcset="https://storage.googleapis.com/labrulez-bucket-strapi-h3hsga3/thumbnail_EST_Analytical_Figure_1_20mg_L_Standard_Chromatogram_7ff795984b.jpg 245w," sizes="100vw" width="1431" height="789"><h4>Conclusions:&nbsp;</h4>This study demonstrated the effectiveness of the Evolution/Centurion purge and trap sampling system. The results passed all of the USEPA Method 524.2 criteria for both linearity and detection limits. Since the Evolution bypasses the water management trap during the four minute desorb process, the amount of water effecting the experiments was limited. Furthermore, the forty to one split ratio at the GC inlet provided excellent detection limits as the system was more sensitive to the low level standard requirements of the method. The lower split rate has an added benefit of reducing laboratory helium consumption when setting it against other system’s higher split ratios. Finally, the precision and percent recovery results showed the reliability of the system in producing accurate experimental findings.

USEPA 524.2 Method Validation Using the Evolution Purge and Trap Concentrator and the Centurion WS Autosampler

<h4>Abstract&nbsp;</h4>Before the advent of orange juice from concentrate, people would fresh squeeze oranges for their juice. Concentrate helped make orange juice easier to make and increased its popularity. Following concentrate, manufacturers used flash pasteurization and created ready to drink orange juice and again sales increased. Due to disease in the orange groves and the possibility of the crops getting destroyed by frost, the production of orange juice has gotten more expensive. The increase in production costs creates competition within the orange juice industry to create an orange juice that the public will enjoy and increase their consumption. This application will look at the flavor compound abundances of three different brands of orange juice using purge and trap concentration.&nbsp;<h4>Introduction</h4>Pasteurization is the first step in the creation of commercial orange juice. This is required in order to kill any harmful bacteria in the juice before it is sold. After the juice is pasteurized, it can be sold. However, since different orange varieties are in season at different times, most juice is squeezed and stored. The storage times vary and with storage there can be other issues. One of these issues is oxidation. Thus, many companies remove the oxygen from the juice before they store it. Between pasteurization and oxygen removal, the juice will lose some of its flavor. This is where juice manufacturers can differentiate themselves.&nbsp;Flavor compounds and amounts can make a substantial difference in the overall taste, acidity and odor of the juice. So, to create a juice that the public wants to buy, it is essential that the analysis of the flavor compounds and the percentage of these flavors be accounted for. Purge and trap is an excellent technique for the extraction of volatile flavor compounds within a liquid matrix. This is an exhaustive technique and generates reproducible results. This application will compare the reproducibility and ratios of flavor compounds in orange juice using the EST Analytical Evolution purge and trap concentrator.&nbsp;<h4>Experimental</h4>The <a target="_blank" rel="noopener noreferrer" href="https://gcms.labrulez.com/products/2160">EST Analytical Evolution purge and trap concentrator </a>was set up with a Vocarb™ 3000 trap while the <a target="_blank" rel="noopener noreferrer" href="https://gcms.labrulez.com/products/2159">Centurion WS autosampler</a> was set to run in soil mode. The sampling system was configured to an <a target="_blank" rel="noopener noreferrer" href="https://gcms.labrulez.com/library?mainauthorItems=10&amp;search=7890A">Agilent 7890A Gas Chromatograph (GC)</a> and <a target="_blank" rel="noopener noreferrer" href="https://gcms.labrulez.com/library?mainauthorItems=10&amp;search=5975C">5975C inert XL Mass Spectrometer (MS) </a>for separation and analysis. As the compounds of interest for this analysis were volatile, a <a target="_blank" rel="noopener noreferrer" href="https://gcms.labrulez.com/library?mainauthorItems=7&amp;search=Restek+Rxi-624+Sil+MS">Restek Rxi® 624 Sil MS</a> 30m X 0.25mm X 1.4µm column was affixed in the GC. Sampling and analysis parameters were optimized and are listed below.<h5>Purge and Trap Parameters</h5><ul><li>Concentrator: EST Encon Evolution</li><li>Trap type: Vocarb 3000</li><li>Valve oven temperature: 150 °C</li><li>Transfer line temperature: 150 °C</li><li>Trap temperature: 35 °C</li><li>Moisture Reduction Trap (MoRT) temperature: 39 °C</li><li>Purge time: 11 min</li><li>Purge flow: 40 mL/min</li><li>Dry purge Temp.: Ambient</li><li>Dry Purge Flow: 40mL/min</li><li>Dry Purge Time: 1.0 min &nbsp;</li><li>Desorb pressure Control: ON</li><li>Desorb Pressure: 6psi</li><li>Desorb time: 0.5 min</li><li>Desorb preheat delay: 5 sec</li><li>Desorb temperature: 260 °C</li><li>MoRT bake temperature: 210 °C</li><li>Bake temperature: 270 °C</li><li>Sparge vessel bake temperature: 120 °C</li><li>Bake time: 8 min</li><li>Bake flow: 85 mL/min</li></ul><h5>Auto-Sampler (EST Centurion WS):</h5><ul><li>Sample type: Soil</li><li>Sample Fill Mode: Syringe</li><li>Water Heater Temp.: 85°C</li><li>Sample Preheat Time: 0.5min</li><li>Sample Preheat Temp.: 40°C</li><li>Soil Valve Temp.: 85°C</li><li>Soil Transfer Line Temp.: 150°C</li><li>Minimizer Time: 2 min</li></ul><h5>GC/MS Parameters</h5><ul><li>System: Agilent 7890/5975C</li><li>Inlet: Split mode, 220 °C, 40:1 split ratio, 12.153 psi head pressure</li><li>Liner: Restek Split liner, 1mm x 6.3 x 78.5</li><li>Column: Restek Rxi-624Sil MS, 30 m × 0.25 mm × 1.4 µm</li><li>Oven program: 45 °C (1 min) → ramp 15 °C/min → 300 °C, hold 5.00 min (total run ~23 min)</li><li>Column flow rate: 1 mL/min helium</li><li>Total flow: 44 mL/min</li><li>Source temperature: 230 °C</li><li>Quadrupole temperature: 150 °C</li><li>Transfer line temperature: 180 °C</li><li>Scan range: m/z 30–350, 4.4 scans/sec</li><li>Solvent delay: 0.7 min</li></ul>Three&nbsp;different&nbsp;orange&nbsp;juice&nbsp;brands&nbsp;were&nbsp;purchased&nbsp;at&nbsp;the&nbsp;local&nbsp;market.&nbsp;&nbsp;Ten&nbsp;milliliters&nbsp;of&nbsp;each&nbsp;orange&nbsp;juice&nbsp;was&nbsp;measured&nbsp;and&nbsp;placed&nbsp;in&nbsp;a&nbsp;40ml&nbsp;vial.&nbsp;&nbsp;Each&nbsp;vial&nbsp;was&nbsp;then&nbsp;deposited&nbsp;in&nbsp;the&nbsp;Centurion&nbsp;WS&nbsp;autosampler&nbsp;to&nbsp;be&nbsp;purged&nbsp;in&nbsp;soil&nbsp;mode&nbsp;and&nbsp;concentrated&nbsp;on&nbsp;a&nbsp;Vocarb&nbsp;3000&nbsp;trap&nbsp;in&nbsp;the&nbsp;Evolution&nbsp;concentrator.&nbsp;Finally,&nbsp;the&nbsp;samples&nbsp;were&nbsp;in&nbsp;run&nbsp;in&nbsp;triplicate&nbsp;in&nbsp;order&nbsp;to&nbsp;ensure&nbsp;the&nbsp;reproducibility&nbsp;of&nbsp;the&nbsp;results.&nbsp;&nbsp;Agilent&nbsp;MassHunter&nbsp;Qualitative&nbsp;Analysis&nbsp;software&nbsp;was&nbsp;used&nbsp;for&nbsp;the&nbsp;determination&nbsp;of&nbsp;the&nbsp;flavor&nbsp;compounds&nbsp;in&nbsp;the&nbsp;juice&nbsp;samples.&nbsp;&nbsp;Table&nbsp;1&nbsp;displays&nbsp;the&nbsp;reproducibility&nbsp;of&nbsp;the&nbsp;sampling&nbsp;process&nbsp;whereas&nbsp;Table&nbsp;2&nbsp;lists&nbsp;a&nbsp;comparison&nbsp;of&nbsp;the&nbsp;flavor&nbsp;compound&nbsp;abundances.&nbsp;&nbsp;<img src="https://storage.googleapis.com/labrulez-bucket-strapi-h3hsga3/EST_Analytical_Table_1_Reproducibility_of_the_Results_fa8fd6f4be.jpg" alt="EST Analytical: Table 1 Reproducibility of the Results" srcset="https://storage.googleapis.com/labrulez-bucket-strapi-h3hsga3/thumbnail_EST_Analytical_Table_1_Reproducibility_of_the_Results_fa8fd6f4be.jpg 245w," sizes="100vw" width="1199" height="754"><img src="https://storage.googleapis.com/labrulez-bucket-strapi-h3hsga3/EST_Analytical_Table_2_Flavor_Compound_Abundance_Summary_d16be388f3.jpg" alt="EST Analytical: Table 2 Flavor Compound Abundance Summary" srcset="https://storage.googleapis.com/labrulez-bucket-strapi-h3hsga3/thumbnail_EST_Analytical_Table_2_Flavor_Compound_Abundance_Summary_d16be388f3.jpg 244w," sizes="100vw" width="1197" height="767">Figure&nbsp;1&nbsp;is&nbsp;a&nbsp;bar&nbsp;graph&nbsp;comparison&nbsp;of&nbsp;the&nbsp;compounds&nbsp;in&nbsp;the&nbsp;three&nbsp;juice&nbsp;brands&nbsp;while&nbsp;Figures&nbsp;2,&nbsp;3&nbsp;and&nbsp;4&nbsp;are&nbsp;the&nbsp;respective&nbsp;chromatograms&nbsp;of&nbsp;the&nbsp;juice&nbsp;samples.<img src="https://storage.googleapis.com/labrulez-bucket-strapi-h3hsga3/EST_Analytical_Figure_1_Bar_Graph_Compound_Abundance_Comparison_f2fd098cdf.jpg" alt="EST Analytical: Figure 1 Bar Graph Compound Abundance Comparison" srcset="https://storage.googleapis.com/labrulez-bucket-strapi-h3hsga3/thumbnail_EST_Analytical_Figure_1_Bar_Graph_Compound_Abundance_Comparison_f2fd098cdf.jpg 221w," sizes="100vw" width="1342" height="950"><img src="https://storage.googleapis.com/labrulez-bucket-strapi-h3hsga3/EST_Analytical_Figure_2_Brand_A_Chromatogram_0d5f5f8daa.jpg" alt="EST Analytical: Figure 2 Brand A Chromatogram" srcset="https://storage.googleapis.com/labrulez-bucket-strapi-h3hsga3/thumbnail_EST_Analytical_Figure_2_Brand_A_Chromatogram_0d5f5f8daa.jpg 245w," sizes="100vw" width="1399" height="871"><img src="https://storage.googleapis.com/labrulez-bucket-strapi-h3hsga3/EST_Analytical_Figure_3_Brand_B_Chromatogram_eefc215bd1.jpg" alt="EST Analytical: Figure 3 Brand B Chromatogram" srcset="https://storage.googleapis.com/labrulez-bucket-strapi-h3hsga3/thumbnail_EST_Analytical_Figure_3_Brand_B_Chromatogram_eefc215bd1.jpg 245w," sizes="100vw" width="1390" height="887"><img src="https://storage.googleapis.com/labrulez-bucket-strapi-h3hsga3/EST_Analytical_Figure_4_Brand_C_Chromatogram_07adab6c82.jpg" alt="EST Analytical: Figure 4 Brand C Chromatogram" srcset="https://storage.googleapis.com/labrulez-bucket-strapi-h3hsga3/thumbnail_EST_Analytical_Figure_4_Brand_C_Chromatogram_07adab6c82.jpg 245w," sizes="100vw" width="1399" height="871"><h4>Conclusions</h4>Using the EST Analytical Evolution purge and trap concentrator coupled to the Centurion WS autosampler to evaluate flavor compounds in orange juice samples proved to be a reliable sampling technique. The results were reproducible and the chromatography was excellent. The three different orange juice brands had very similar chromatograms; however upon further analysis many subtle differences in the abundances of the flavor compounds could be discerned. Traditionally, headspace and solid phase micro extraction sampling are used for this type of analysis. However, the purge and trap sampling technique used for this examination offered an excellent alternative for the determination of the volatile components in a juice matrix.

Flavor Compound Abundances in Orange Juice Comparison Using Purge and Trap

<h4>Abstract&nbsp;</h4>Environmental laboratories are always searching for techniques to increase productivity. However, environmental methods demand a large amount of background information in order to ensure sampling and analysis is compliant. The determination of <a target="_blank" rel="noopener noreferrer" href="https://gcms.labrulez.com/library?mainauthorItems=45&amp;search=VOC">Volatile Organic Compounds (VOCs) </a>in the United States Environmental Protection Agency (USEPA) <a target="_blank" rel="noopener noreferrer" href="https://gcms.labrulez.com/library?mainauthorItems=45&amp;search=Method+8260">Method 8260</a> encompasses many different matrices and in doing so has numerous sampling, quality control, and calibration requirements. The matrices of Method 8260 samples can also vary from air to sludge and from clean to extremely contaminated. Furthermore, the method has an extensive calibration range. All of these factors play into the complexity of sampling and analysis thus, creating ways to streamline sampling while still maintaining sample integrity and method compliance is always of interest to environmental laboratories.<h4>Introduction</h4>In order to run Method 8260 samples, a bromofluorobenzene (BFB) tune standard, matrix blank, calibration standard, and laboratory control standard all have to be run and pass method requirements every twelve hours. With the exception of the BFB standard, the other standards and blank matrices have to correspond to the samples to be analyzed. Due to this constraint, the analyst is required to run another three samples if the matrix is changed within the twelve hour time window. Moreover, the calibration must also match the sample matrix. These requirements are very time consuming and can limit laboratory profits. This application note will demonstrate a patented automated water sampling mode using the soil sampling station of the autosampler thus eliminating the need to have separate calibrations and standards for waters and soils.&nbsp;<h4>Discussion</h4>There are a number or techniques that can enable an analyst to save time in an environmental lab. Analysts can decrease analytical trap bake times, change sample purge time and flow, utilize a dual sampling system for one GC/MS, etc. However, one of the most basic ways to save time is by reducing the number of required curves and standards needed.EST Analytical has designed a patented, automated water sampling mode that will allow environmental laboratories to run water samples in the soil mode. Thus, water and soil curves, standards, blanks and samples can use the same sampling parameters. (See steps 1, 2, and 3 below). This innovative sampling mode would eliminate the need to have separate curves, standards, etc. for soils and waters, thus saving laboratories time and money. Please note that this procedure may only be used with auditor approval.<img src="https://storage.googleapis.com/labrulez-bucket-strapi-h3hsga3/EST_Analytical_Experimental_9f34a58017.jpg" alt="EST Analytical: Sampling" srcset="https://storage.googleapis.com/labrulez-bucket-strapi-h3hsga3/thumbnail_EST_Analytical_Experimental_9f34a58017.jpg 245w," sizes="100vw" width="1386" height="861"><h4>Experimental</h4>The sampling system used for this study was the <a target="_blank" rel="noopener noreferrer" href="https://gcms.labrulez.com/products/2159">EST Analytical Centurion WS autosampler</a> and <a target="_blank" rel="noopener noreferrer" href="https://gcms.labrulez.com/products/2160">Evolution concentrator</a>. The concentrator was affixed with a Vocarb 3000 trap and connected to an <a target="_blank" rel="noopener noreferrer" href="https://gcms.labrulez.com/library?mainauthorItems=10&amp;search=7890A">Agilent 7890A GC</a> and <a target="_blank" rel="noopener noreferrer" href="https://gcms.labrulez.com/library?mainauthorItems=10&amp;search=5975C">5975 inert XL MS</a>. The GC was configured with a <a target="_blank" rel="noopener noreferrer" href="https://gcms.labrulez.com/library?mainauthorItems=7&amp;search=Restek+Rxi-624+Sil+MS">Restek Rxi-624 Sil MS</a> 30m x 0.25mm x 1.4µm column. The experiments were run using the extraction mode of the Centurion WS. Sampling method parameters and GC/MS parameters are listed below.<h5>Purge and Trap Parameters</h5><ul><li>Concentrator: EST Evolution</li><li>Trap type: Vocarb 3000</li><li>Valve oven temperature: 150 °C</li><li>Transfer line temperature: 150 °C</li><li>Trap temperature: 35 °C</li><li>Moisture Reduction Trap (MoRT) temperature: 39 °C</li><li>Purge time: 11 min</li><li>Purge flow: 40 mL/min</li><li>Dry purge Temp.: Ambient</li><li>Dry Purge Flow: 40mL/min</li><li>Dry Purge Time: 1.0 min &nbsp;</li><li>Desorb pressure Control: ON</li><li>Desorb Pressure: 5psi</li><li>Desorb time: 0.5 min</li><li>Desorb preheat delay: 5 sec</li><li>Desorb temperature: 260 °C</li><li>MoRT bake temperature: 230 °C</li><li>Bake temperature: 270 °C</li><li>Sparge vessel bake temperature: 120 °C</li><li>Bake time: 8 min</li><li>Bake flow: 40 mL/min</li></ul><h5>Auto-Sampler (EST Centurion WS):</h5><ul><li>Sample type: Water Extraction</li><li>Sample Fill Mode: Syringe</li><li>Sample Volume: 10mL</li><li>IS Volume: 5µl</li><li>Needle Rinse Time: 20 sec</li><li>Needle Sweep Time: 20 sec</li><li>Concentrator Desorb Time: 0.5 min</li><li>Syringe Rinse: On/12mL</li><li>Number of Syringe Rinses: 2</li><li>Sparge Rinse Time: Off</li><li>Water Heater Temp.: 85°C</li></ul><h5>GC/MS Parameters</h5><ul><li>System: Agilent 7890/5975 inert XL</li><li>Inlet: Split mode, 200 °C, 40:1 split ratio, 12.153 psi head pressure</li><li>Column: Restek Rxi-624Sil MS, 30 m × 0.25 mm × 1.4 µm</li><li>Oven program: 45 °C (1 min) → ramp 15 °C/min → 220 °C, hold 1.3 min</li><li>Column flow rate: 1 mL/min helium</li><li>Total flow: 44 mL/min</li><li>Source temperature: 230 °C</li><li>Quadrupole temperature: 150 °C</li><li>Transfer line temperature: 180 °C</li><li>Scan range: m/z 35–265, 3.12 scans/sec</li><li>Solvent delay: 0.7 min</li></ul>The USEPA Method 8260 standards were acquired from Restek. The linear range of the water extraction experiment was established by running a nine point calibration curve with a range of 0.5 to 200ppb. Method detection limits were also established for each compound by examining seven replicate standards of the low calibration point. Finally, precision and accuracy were determined by running seven replicate midpoint standards. Figure 1 displays a 50ppb Method 8260 standard chromatogram of a water sample run in soil mode and experimental results are listed in Table 1.<img src="https://storage.googleapis.com/labrulez-bucket-strapi-h3hsga3/EST_Analytical_Obrazek_1_Chromatogram_50_ppb_vzorku_vody_analyzovaneho_v_rezimu_puda_55ffcb4ba3.jpg" alt="EST Analytical: Figure 1: 50ppb Chromatogram of a Water Sample Run in Soil Mode" srcset="https://storage.googleapis.com/labrulez-bucket-strapi-h3hsga3/thumbnail_EST_Analytical_Obrazek_1_Chromatogram_50_ppb_vzorku_vody_analyzovaneho_v_rezimu_puda_55ffcb4ba3.jpg 245w," sizes="100vw" width="1444" height="514"><img src="https://storage.googleapis.com/labrulez-bucket-strapi-h3hsga3/EST_Analytical_Tabulka_3_Vysledky_experimentu_cast_1_7cadc58cda.jpg" alt="EST Analytical: Table 3: Experimental Results_part 1" srcset="https://storage.googleapis.com/labrulez-bucket-strapi-h3hsga3/thumbnail_EST_Analytical_Tabulka_3_Vysledky_experimentu_cast_1_7cadc58cda.jpg 215w," sizes="100vw" width="1568" height="1143"><img src="https://storage.googleapis.com/labrulez-bucket-strapi-h3hsga3/EST_Analytical_Tabulka_3_Vysledky_experimentu_cast_2_f676814e52.jpg" alt="EST Analytical: Table 3: Experimental Results_Part 2" srcset="https://storage.googleapis.com/labrulez-bucket-strapi-h3hsga3/thumbnail_EST_Analytical_Tabulka_3_Vysledky_experimentu_cast_2_f676814e52.jpg 245w," sizes="100vw" width="1571" height="616"><h4>Conclusion</h4>The patented sampling process of the Centurion WS proved to be a reliable and accurate sampling method for running water samples in the soil mode. The curve linearity and method detection limits both met USEPA Method 8260 requirements, and the precision and accuracy results were excellent. The water extraction option offered with the Centurion WS will save laboratories time and money because only one set of standards, curves, etc. is required for both water and soil samples.

A Single Calibration Method for Water AND Soil Samples Performing EPA Method 8260

<h4>Abstract</h4>Strong or weak, light or dark, black or with cream; everyone who drinks coffee has a preference. Today, there are not only the choices of what you would like in your coffee, but also how you would like it brewed. Do you prefer the old fashioned percolator or the straight forward brewed coffee? Or do you like the new coffee by the cup makers or the instant coffees? There are so many options! This study will analyze four different instant coffee blends for some of their respective flavors using a purge and trap concentrator.<h4>Discussion</h4>Most of us who drink coffee know our preferences. We know which blend we like, what strength and definitely what we like in our coffee. However, most of us do not think about the flavors that go into our coffee that help us define our preferences. Coffee manufacturers, on the other hand, are working diligently to create a new blend or a more satisfying flavor that would make us want to choose their coffee over another maker.This study will look at four different blends of coffee and some of the compounds that contribute to the flavor of the blend. Using purge and trap sampling, the flavor compounds were purged out of the coffee and trapped onto an adsorbent trap. The analytes were then transferred to a Gas Chromatograph/Mass Spectrometer (GC/MS) for analysis. The study focused on six flavor compounds: the spicy smoky aroma of 2-methylfuran, the spicy caramel, almond odor of 5-methylfurfural, the buttery scent provided by the addition of 2,3-butanedione and 2,3-pentanedione, and the impact of the two and three methyl butanals giving the dark chocolate malty flavor to the coffee.<img src="https://storage.googleapis.com/labrulez-bucket-strapi-h3hsga3/EST_Analytical_Purge_and_Trap_Analysis_of_Coffee_Flavors_by_Purge_and_Trap_Sampling_ca25beef60_1_acf9fc0b4f.jpg" alt="EST Analytical: Encon Evolution Purge and Trap Concentrator and Centurion WS Autosampler" srcset="https://storage.googleapis.com/labrulez-bucket-strapi-h3hsga3/thumbnail_EST_Analytical_Purge_and_Trap_Analysis_of_Coffee_Flavors_by_Purge_and_Trap_Sampling_ca25beef60_1_acf9fc0b4f.jpg 197w," sizes="100vw" width="668" height="531"><h4>Experimental</h4>The EST Analytical <a target="_blank" rel="noopener noreferrer" href="https://gcms.labrulez.com/products/2160">Encon Evolution Purge and Trap Concentrator</a> and <a target="_blank" rel="noopener noreferrer" href="https://gcms.labrulez.com/products/2159">Centurion WS Autosampler</a> were interfaced to a GC/MS. The Centurion WS was run in the soil mode and the purge and trap concentrator was configured with a Vocarb 3000 (K) analytical trap. The column selected for this study was an Rtx-1 60 m × 0.25 mm × 1 µm. Sampling method parameters and GC/MS parameters are listed below.<h5>Purge and Trap Parameters</h5><ul><li>Concentrator: EST Encon Evolution</li><li>Trap type: Vocarb 3000</li><li>Valve oven temperature: 150 °C</li><li>Transfer line temperature: 150 °C</li><li>Trap temperature: 35 °C</li><li>Moisture Reduction Trap (MoRT) temperature: 39 °C</li><li>Purge time: 11 min</li><li>Purge flow: 40 mL/min</li><li>Dry purge Temp.: Ambient</li><li>Dry Purge Flow: 50mL/min</li><li>Dry Purge Time: 1.0 min &nbsp;</li><li>Desorb pressure Control: ON</li><li>Desorb Pressure: 5psi</li><li>Desorb time: 0.5 min</li><li>Desorb preheat delay: 5 sec</li><li>Desorb temperature: 260 °C</li><li>MoRT bake temperature: 230 °C</li><li>Bake temperature: 260 °C</li><li>Sparge vessel bake temperature: 120 °C</li><li>Bake time: 8 min</li><li>Bake flow: 85 mL/min</li></ul><h5>Auto-Sampler (EST Centurion WS):</h5><ul><li>Sample type: Soil</li><li>Sample Fill Mode: loop</li><li>Sample Volume: 10mL</li><li>Sample Prime Time: 5 sec</li><li>Loop Equilibration Time: 10 sec</li><li>Sample Transfer Time: 15 sec</li><li>Sample Loop Rinse: Off</li><li>Sample Loop Sweep Time: 15 sec</li><li>Number of Sparge Rinses: 1</li><li>Rinse Volume: 5mL</li><li>Rinse Transfer Time: 20 sec</li><li>Rinse Drain Time: 20 sec</li><li>Number of Foam Rinse Cycles: 1</li><li>Water Heater Temp.: 85°C</li><li>Sample Preheat Temp.: 40°C</li><li>Soil Valve Temp.: 85°C</li><li>Soil Transfer Line Temp.: 150°C &nbsp;</li></ul><h5>GC/MS Parameters</h5><ul><li>System: <a target="_blank" rel="noopener noreferrer" href="https://gcms.labrulez.com/library?mainauthorItems=10&amp;search=7890%2F5975">Agilent 7890/5975</a></li><li>Inlet: Split mode, 200 °C, 20:1 split ratio, 16.041 psi head pressure</li><li>Column: Rtx-1 60m x 0.25mm I.D. 1.0µm film thickness</li><li>Oven program: 35 °C (1 min) → ramp 4 °C/min → 230 °C, total run time of 49.75 min</li><li>Column flow rate: 1 mL/min helium</li><li>Total flow: 26.0 mL/min</li><li>Source temperature: 230 °C</li><li>Quadrupole temperature: 150 °C</li><li>Transfer line temperature: 180 °C</li><li>Scan range: m/z 35–265, 3.12 scans/sec</li><li>Solvent delay: 0.0 min</li></ul>The GC column was acquired from Restek while the instant coffees were purchased at a local retailer. The four roasts chosen for this study ranged from light to dark. One half of a gram of each coffee was dissolved in 40 mL of de-ionized water at room temperature. The vials were shaken in order to fully dissolve the coffee. Next, 5 mL of each coffee mixture were run in the soil mode using the Centurion WS autosampler and the Encon Evolution purge and trap concentrator. Each coffee was run in triplicate in order to verify the results. Figures 1 through 3 display a bar graph comparison of the flavors in each coffee blend. Chromatograms of the coffee blends are shown in Figures 4 through 7.<img src="https://storage.googleapis.com/labrulez-bucket-strapi-h3hsga3/EST_Analaytical_Figure_1_Buttery_Compound_Comparison_08f6fd5d05.jpg" alt="EST Analytical: Figure 1 Buttery Compound Comparison" srcset="https://storage.googleapis.com/labrulez-bucket-strapi-h3hsga3/thumbnail_EST_Analaytical_Figure_1_Buttery_Compound_Comparison_08f6fd5d05.jpg 245w," sizes="100vw" width="905" height="544"><img src="https://storage.googleapis.com/labrulez-bucket-strapi-h3hsga3/EST_Analaytical_Figure_2_Smoky_and_Spicy_Caramel_Compound_Comparison_6940d35e36.jpg" alt="EST Analytical: Figure 2 Smoky and Spicy Caramel Compound Comparison" srcset="https://storage.googleapis.com/labrulez-bucket-strapi-h3hsga3/thumbnail_EST_Analaytical_Figure_2_Smoky_and_Spicy_Caramel_Compound_Comparison_6940d35e36.jpg 245w," sizes="100vw" width="905" height="545"><img src="https://storage.googleapis.com/labrulez-bucket-strapi-h3hsga3/EST_Analaytical_Figure_3_Dark_Chocolate_Malty_Compound_Comparison_cbee579baf.jpg" alt="EST Analytical: Figure 3 Dark Chocolate - Malty Compound Comparison" srcset="https://storage.googleapis.com/labrulez-bucket-strapi-h3hsga3/thumbnail_EST_Analaytical_Figure_3_Dark_Chocolate_Malty_Compound_Comparison_cbee579baf.jpg 245w," sizes="100vw" width="905" height="545"><img src="https://storage.googleapis.com/labrulez-bucket-strapi-h3hsga3/EST_Analaytical_Figure_4_Light_Roast_Chromatogram_8380d110a6.jpg" alt="EST Analytical: Figure 4 Light Roast Chromatogram" srcset="https://storage.googleapis.com/labrulez-bucket-strapi-h3hsga3/thumbnail_EST_Analaytical_Figure_4_Light_Roast_Chromatogram_8380d110a6.jpg 245w," sizes="100vw" width="953" height="375"><img src="https://storage.googleapis.com/labrulez-bucket-strapi-h3hsga3/EST_Analaytical_Figure_5_Medium_Roast_Chromatogram_9a97a58a74.jpg" alt="EST Analytical: Figure 5 Medium Roast Chromatogram" srcset="https://storage.googleapis.com/labrulez-bucket-strapi-h3hsga3/thumbnail_EST_Analaytical_Figure_5_Medium_Roast_Chromatogram_9a97a58a74.jpg 245w," sizes="100vw" width="886" height="401"><img src="https://storage.googleapis.com/labrulez-bucket-strapi-h3hsga3/EST_Analaytical_Figure_6_Medium_Dark_Roast_Chromatogram_eb6a37cd16.jpg" alt="EST Analytical: Figure 6 Medium Dark Roast Chromatogram" srcset="https://storage.googleapis.com/labrulez-bucket-strapi-h3hsga3/thumbnail_EST_Analaytical_Figure_6_Medium_Dark_Roast_Chromatogram_eb6a37cd16.jpg 245w," sizes="100vw" width="877" height="410"><img src="https://storage.googleapis.com/labrulez-bucket-strapi-h3hsga3/EST_Analaytical_Figure_7_Dark_Roast_Chromatogram_79711f7858.jpg" alt="EST Analytical: Figure 7 Dark Roast Chromatogram" srcset="https://storage.googleapis.com/labrulez-bucket-strapi-h3hsga3/thumbnail_EST_Analaytical_Figure_7_Dark_Roast_Chromatogram_79711f7858.jpg 245w," sizes="100vw" width="856" height="412"><h4>Conclusion</h4>The lightest roast had the most buttery and dark chocolate/malty flavors while the darkest roast had more of the smoky flavor. Surprisingly, the darkest roast and the medium roast had similar proportions of the flavor compounds with the exception of the smoky flavor. While the light roast had large amounts of the flavors tested for, the chromatography of the light roast was much simpler than that of the darker roasts. Overall, the Encon Evolution Purge and Trap Concentrator in conjunction with the Centurion WS Autosampler proved to be an excellent system for sampling coffee. The results were reproducible and provided a lot of information on the flavors of the respective coffees.

Analysis of Coffee Flavors by Purge and Trap Sampling

Analysis of field samples in environmental laboratories can sometimes be complicated by how contaminated or “hot” the sample is. Many times “hot” samples have to be diluted in order to verify the level of contamination in the sample. The process of diluting samples is a time consuming process that can sometimes lead to human error when calculations are incorrect. A further problem is the loss of volatile organic compounds as the sample vial needs to be opened in order to perform the dilution.&nbsp;This poster will examine the benefits of automated dilutions. Since the syringe option of this system has the unique ability to dilute samples from two times to 400 times the original concentration, this study will examine the precision and accuracy for an array of dilutions in this comprehensive range. The dilution data will be compared to a manually prepared 50ppb calibration standard in order to determine the accuracy of the results. The precision will be established by examining four sequential dilutions and the percent relative standard deviation of the compounds’ respective area counts. Furthermore, in order to demonstrate the linearity of the dilutions, a calibration curve will be presented using the automated dilution option to prepare 200ppb standards for a calibration range of 0.5ppb (400x) to 200ppb (1x).<h4>Discussion&nbsp;</h4>Environmental laboratories often have to dilute field samples due to the analytes of interest having concentrations over the highest calibration level of the curve. In order to dilute these samples, the vial has to be opened and a portion of the sample has to be diluted manually and re-analyzed. Opening the vial can compromise the integrity of the sample as volatiles are lost when the seal of the vial is broken.&nbsp;EST Analytical has developed a syringe feature for the Centurion Autosampler that can dilute samples up to 400 times the original concentration. This feature is fully programmable and the sample vial does not have to be compromised in order to dilute the sample because the dilution process is automated. The sealed vial can be placed in the sample tray while the Centurion does all of the work.&nbsp;<h4>Experimental&nbsp;</h4>The <a target="_blank" rel="noopener noreferrer" href="https://gcms.labrulez.com/products/2159">Centurion WS autosampler</a> was configured with an <a target="_blank" rel="noopener noreferrer" href="https://gcms.labrulez.com/products/2160">Encon Evolution concentrator</a>. A Vocarb 3000 (K) trap was installed in the Evolution. Finally, the sampling system was connected to a GC/MS for sample analysis. The GC column employed for this study was an Rxi-624Sil MS 30m x 0.25mm x 1.4µm. Dilution Factors, Purge and Trap, and GC/MS parameters are listed below.<h5>Standard Concentration &amp; Dilution Factors</h5><ul><li>100ppb: 2x</li><li>250ppb: 5x</li><li>500ppb: 10x</li><li>2.5ppm: 50x</li><li>5ppm: 100x</li><li>10ppm: 200x</li><li>20ppm: 400x</li></ul><h5>Purge and Trap Parameters</h5><ul><li>Concentrator: EST Encon Evolution</li><li>Trap type: Vocarb 3000</li><li>Valve oven temperature: 150 °C</li><li>Transfer line temperature: 150 °C</li><li>Trap temperature: 35 °C</li><li>Moisture Reduction Trap (MoRT) temperature: 39 °C</li><li>Purge time: 11 min</li><li>Purge flow: 40 mL/min</li><li>Dry purge Temp.: Ambient</li><li>Dry Purge Flow: 40mL/min</li><li>Dry Purge Time: 1.0 min &nbsp;</li><li>Desorb pressure Control: ON</li><li>Desorb Pressure: 5psi</li><li>Desorb time: 0.5 min</li><li>Desorb preheat delay: 5 sec</li><li>Desorb temperature: 260 °C</li><li>MoRT bake temperature: 230 °C</li><li>Bake temperature: 265 °C</li><li>Sparge vessel bake temperature: 120 °C</li><li>Bake time: 8 min</li><li>Bake flow: 40 mL/min</li></ul><h5>GC/MS Parameters</h5><ul><li>System: <a target="_blank" rel="noopener noreferrer" href="https://gcms.labrulez.com/library?mainauthorItems=10&amp;search=7890%2F5975">Agilent 7890/5975</a></li><li>Inlet: Split mode, 200 °C, 40:1 split ratio, 12.153 psi head pressure</li><li>Column: Rxi-624Sil MS 30m x 0.25mm I.D. 1.4µm film thickness</li><li>Oven program: 45 °C (1 min) → ramp 18 °C/min → 220 °C, hold for 0.3 min</li><li>Column flow rate: 1 mL/min helium</li><li>Total flow: 44.0 mL/min</li><li>Source temperature: 230 °C</li><li>Quadrupole temperature: 150 °C</li><li>Transfer line temperature: 180 °C</li><li>Scan range: m/z 35–265, 3.12 scans/sec</li><li>Solvent delay: 0.7 min</li></ul>A 9 point calibration curve was manually prepared and run from 0.5 to 200ppb with standards ordered from Restek. After a linear calibration curve was established, a 50ppb calibration standard was run to establish instrument response for the compounds being analyzed. Next, a series of dilutions were run and compared with the initial 50ppb calibration standard. Each dilution factor was run four times with blanks in between. The final concentration of each dilution was 50ppb. The precision and accuracy of the dilutions are listed in Tables 4 and 5 and Figures 1 and 2 display the chromatograms of two of the dilutions.<img src="https://storage.googleapis.com/labrulez-bucket-strapi-h3hsga3/EST_Analytical_Figure_1_Overlay_of_50ppb_1_X_and_2500ppb_50x_Standards_29d90b4107.jpg" alt="EST Analytical: Figure 1 - Overlay of 50ppb (1X) and 2500ppb (50x) Standards" srcset="https://storage.googleapis.com/labrulez-bucket-strapi-h3hsga3/thumbnail_EST_Analytical_Figure_1_Overlay_of_50ppb_1_X_and_2500ppb_50x_Standards_29d90b4107.jpg 245w," sizes="100vw" width="1023" height="383"><img src="https://storage.googleapis.com/labrulez-bucket-strapi-h3hsga3/EST_Analytical_Figure_2_Overlay_of_50ppb_1_X_and_10000ppb_200x_Standards_7f939589b9.jpg" alt="EST Analytical: Figure 2 - Overlay of 50ppb (1X) and 10000ppb (200x) Standards" srcset="https://storage.googleapis.com/labrulez-bucket-strapi-h3hsga3/thumbnail_EST_Analytical_Figure_2_Overlay_of_50ppb_1_X_and_10000ppb_200x_Standards_7f939589b9.jpg 245w," sizes="100vw" width="1073" height="383"><img src="https://storage.googleapis.com/labrulez-bucket-strapi-h3hsga3/EST_Analytical_Table_4_Experimental_Results_2x_5x_10x_and_50x_dilutions_d81be1942f.jpg" alt="EST Analytical: Table 4 - Experimental Results (2x, 5x, 10x, and 50x dilutions)" srcset="https://storage.googleapis.com/labrulez-bucket-strapi-h3hsga3/thumbnail_EST_Analytical_Table_4_Experimental_Results_2x_5x_10x_and_50x_dilutions_d81be1942f.jpg 150w," sizes="100vw" width="1173" height="1220"><img src="https://storage.googleapis.com/labrulez-bucket-strapi-h3hsga3/EST_Analytical_Table_5_Experimental_Results_100x_200x_and_400x_dilutions_f29762c72e.jpg" alt="EST Analytical: Table 5 - Experimental Results (100x, 200x and 400x dilutions)" srcset="https://storage.googleapis.com/labrulez-bucket-strapi-h3hsga3/thumbnail_EST_Analytical_Table_5_Experimental_Results_100x_200x_and_400x_dilutions_f29762c72e.jpg 124w," sizes="100vw" width="972" height="1226">Finally, a nine point calibration curve was run by setting up the system to do the dilutions. The curve was run using nine 40ml vials filled to volume with a 200ppb calibration standard and doing serial dilutions on the standards. For example, the 200ppb was diluted 400x for the 0.5ppb standard, 200x for the 1.0ppb standard, etc. See Table 6 for the curve dilutions and Table 7 for the curve linearity and compound responses.<img src="https://storage.googleapis.com/labrulez-bucket-strapi-h3hsga3/EST_Analytical_Table_6_Syringe_Curve_Dilutions_4237e1d568.jpg" alt="EST Analytical: Table 6 Syringe Curve Dilutions" srcset="https://storage.googleapis.com/labrulez-bucket-strapi-h3hsga3/thumbnail_EST_Analytical_Table_6_Syringe_Curve_Dilutions_4237e1d568.jpg 245w," sizes="100vw" width="785" height="381"><img src="https://storage.googleapis.com/labrulez-bucket-strapi-h3hsga3/EST_Analytical_Table_7_Automated_Dilution_Curve_Results_356126f34f.jpg" alt="EST Analytical: Table 7 Automated Dilution Curve Results" srcset="https://storage.googleapis.com/labrulez-bucket-strapi-h3hsga3/thumbnail_EST_Analytical_Table_7_Automated_Dilution_Curve_Results_356126f34f.jpg 138w," sizes="100vw" width="927" height="1050"><h4>Conclusions&nbsp;</h4>The Centurion WS with the syringe option displayed remarkable precision and accuracy from as low as the 2x dilution to as high as 400x dilution. On the whole, the average precision of the instrument was less than 5%RSD while the overall accuracy was 90% to 110%. The system also is capable of curve automation with the average %RSD of below 10% for a 9 point curve from 0.5ppb to 200ppb. The automated dilution feature of the Centurion WS with the syringe option would enable laboratories to run samples more efficiently and the since the samples would not need to be compromised in order to perform dilutions, the accuracy of the experimental results would improve.

Automated Dilutions Using the Centurion Autosampler

<h4>Abstract&nbsp;</h4>The United States Environmental Protection Agency (USEPA) Method 8260 is used in order to ascertain volatile organic compounds in waters, soils and solid waste samples. Often times, soil and solid waste samples are so highly contaminated the sample needs to be dispersed in methanol. Sample collection for contaminated soils can be obtained in two ways. One, dispersing a bulk soil sample into a 40ml vial and adding methanol in the lab or two, sending preweighed vials with a septum sealed cap that already contains the pre-requisite methanol out in the field for soil sampling. No matter how the soil sample is dispersed in methanol, an aliquot of the methanol extract needs to be added to water and purged using USEPA Method 5030. This application will investigate automated sampling of methanol soil extractions.Introduction: Environmental labs are required to perform methanol extractions on highly contaminated solid waste samples. Additionally, these extractions are used for difficult matrices, for example oily waste samples, that are also soluble in methanol. Due to the variety of matrices that can be extracted with methanol there are assorted hurdles to cross in order to automate the sampling process. One of these obstacles is how the matrix can absorb the extraction solvent. For example, many soil samples require more methanol; due to the soil expanding with the solvent addition. Adding more methanol aids in rectifying this issue however, when automating sampling, the added methanol coupled with the soil expansion needs to be accommodated. For this reason, EST Analytical created software for the Centurion WS that allows the user to program the needle depth to different distances. In doing this, laboratories are able to sample soils at higher depths in order to adjust for sample absorption and at lower depths for samples that do not require the added solvent. In order to test volatile compounds in methanol extractions, a portion of the extract needs to be sampled from the vial, diluted, and purged on a purge and trap concentrator. This examination will look at the automated sampling of three different soil matrices.<h4>Experimental</h4>The <a target="_blank" rel="noopener noreferrer" href="https://gcms.labrulez.com/products/2159">Centurion WS autosampler</a> with the syringe option and the <a target="_blank" rel="noopener noreferrer" href="https://gcms.labrulez.com/products/2160">Evolution purge and trap concentrator</a> were set up to run methanol extractions. Since this is a volatile analysis, a Vocarb 3000 (K) trap was used for the analytical trap. The sampling system was configured to an <a target="_blank" rel="noopener noreferrer" href="https://gcms.labrulez.com/library?mainauthorItems=10&amp;search=7890A">Agilent 7890A Gas Chromatograph (GC) </a>and an <a target="_blank" rel="noopener noreferrer" href="https://gcms.labrulez.com/library?mainauthorItems=10&amp;search=5975C">Agilent 5975C inert XL Mass Spectrometer (MS)</a>. The column selected for this analysis was a Restek Rxi®-624 Sil MS, with dimensions of 30m x 0.25mm I.D. x 1.4µm film thickness. Experimental parameters used for this analysis are listed below.<h5>Purge and Trap Parameters</h5><ul><li>Concentrator: EST Encon Evolution</li><li>Trap type: Vocarb 3000</li><li>Valve oven temperature: 150 °C</li><li>Transfer line temperature: 150 °C</li><li>Trap temperature: 35 °C</li><li>Moisture Reduction Trap (MoRT) temperature: 39 °C</li><li>Purge time: 11 min</li><li>Purge flow: 40 mL/min</li><li>Dry purge Temp.: Ambient</li><li>Dry Purge Flow: 40mL/min</li><li>Dry Purge Time: 1.0 min &nbsp;</li><li>Desorb pressure Control: ON</li><li>Desorb Pressure: 6psi</li><li>Desorb time: 0.5 min</li><li>Desorb preheat delay: 15 sec</li><li>Desorb temperature: 260 °C</li><li>MoRT bake temperature: 210 °C</li><li>Bake temperature: 270 °C</li><li>Sparge vessel bake temperature: 120 °C</li><li>Bake time: 8 min</li><li>Bake flow: 85 mL/min</li></ul><h5>Purge and Trap Auto-Sampler: EST Centurion WS</h5><ul><li>Sample Type: Water</li><li>Water Volume: 5ml</li><li>Sample Prime Time: 5 sec</li><li>Loop Equilibration Time: 5 sec</li><li>Sample Transfer Time: 15 sec.</li><li>Syringe Rinse: On/6 ml</li><li>Number of Syringe Rinses: 2</li><li>Sample Loop Rinse: On/15 sec</li><li>Sample Sweep Time: 15 sec</li><li>Number of Sparge Rinses: On/2</li><li>Rinse Volume: 5 ml</li><li>Rinse Transfer Time: 15 sec</li><li>Rinse Drain Time: 25 sec</li><li>Internal Standard Vol.: 5 µl</li><li>Extraction: MeOH Prep A (Sand and Clay)</li><li>Extraction: MeOH Prep B (Potting Soil)&nbsp;</li></ul><h5>GC/MS Parameters</h5><ul><li>System: <a target="_blank" rel="noopener noreferrer" href="https://gcms.labrulez.com/library?mainauthorItems=10&amp;search=7890%2F5975">Agilent 7890/5975</a></li><li>Inlet: Split/splitless mode, 220 °C, 40:1 split ratio, 12.153 psi inlet head pressure</li><li>Column: Rxi-624Sil MS 30m x 0.25mm I.D. 1.4µm film thickness</li><li>Oven program: 45 °C (1 min) → ramp 15 °C/min → 220 °C, hold for 1.33 min, 14 min run time</li><li>Column flow rate: 1 mL/min helium</li><li>Total flow: 44.0 mL/min</li><li>Source temperature: 230 °C</li><li>Quadrupole temperature: 150 °C</li><li>Transfer line temperature: 180 °C</li><li>Scan range: m/z 35–300, 5.2 scans/sec</li><li>Solvent delay: 0.7 min</li></ul>The EPA method 8260 standards were acquired from Restek while the purge and trap grade methanol was procured from JTBaker. A nine point methanol curve was established from 0.5 to 200µg/L. Next Method Detection Limits (MDLs) were found running seven replicates of the low point on the curve. Precision and accuracy was determined by examining seven replicates of the 50µg/L standard. Table 3 displays the curve, MDL and precision and accuracy results. A set of three spiked sand matrix samples were used to establish the accuracy of the automated extraction at a 50µg/L concentration, see Table 4.<img src="https://storage.googleapis.com/labrulez-bucket-strapi-h3hsga3/EST_Analytical_Table_3_Curve_MDL_and_Precision_and_Accuracy_Results_38f2c858a9.jpg" alt="EST Analytical: Table 3 - Curve, MDL and Precision and Accuracy Results." srcset="https://storage.googleapis.com/labrulez-bucket-strapi-h3hsga3/thumbnail_EST_Analytical_Table_3_Curve_MDL_and_Precision_and_Accuracy_Results_38f2c858a9.jpg 159w," sizes="100vw" width="1102" height="1083"><img src="https://storage.googleapis.com/labrulez-bucket-strapi-h3hsga3/EST_Analytical_Table_4_Results_of_Automated_Extraction_of_a_Sand_Matrix_3874d74191.jpg" alt="EST Analytical: Table 4 - Results of Automated Extraction of a Sand Matrix" srcset="https://storage.googleapis.com/labrulez-bucket-strapi-h3hsga3/thumbnail_EST_Analytical_Table_4_Results_of_Automated_Extraction_of_a_Sand_Matrix_3874d74191.jpg 91w," sizes="100vw" width="741" height="1267">Finally, sand, clay and soil matrices were extracted in order to compare the chromatography of the automated extractions using different matrices. The matrix comparison required 5 grams of soil and 15mls of methanol due to the potting soils’ absorption of the methanol. Thus, in order to make a direct comparison, all of the matrices were spiked with the same volume of standard and extracted with 15mls of methanol. Figure 1 displays a comparison of the three matrices and their respective interaction with the extraction solvent and Figure 2 shows the chromatograms of the three matrices.<img src="https://storage.googleapis.com/labrulez-bucket-strapi-h3hsga3/EST_Analytical_Figure_1_Image_of_5g_of_soil_matrices_in_15mls_of_Methanol_fc02a00c9d.jpg" alt="EST Analytical: Figure 1 - Image of 5g of soil matrices in 15mls of Methanol" srcset="https://storage.googleapis.com/labrulez-bucket-strapi-h3hsga3/thumbnail_EST_Analytical_Figure_1_Image_of_5g_of_soil_matrices_in_15mls_of_Methanol_fc02a00c9d.jpg 185w," sizes="100vw" width="565" height="477"><img src="https://storage.googleapis.com/labrulez-bucket-strapi-h3hsga3/EST_Analytical_Figure_2_Chromatograms_of_Automated_Extraction_of_Sand_Clay_and_Soil_53e50f4fc4.jpg" alt="EST Analytical: Figure 2 - Chromatograms of Automated Extraction of Sand, Clay and Soil" srcset="https://storage.googleapis.com/labrulez-bucket-strapi-h3hsga3/thumbnail_EST_Analytical_Figure_2_Chromatograms_of_Automated_Extraction_of_Sand_Clay_and_Soil_53e50f4fc4.jpg 245w," sizes="100vw" width="1396" height="702"><h4>Conclusions</h4>The system produced excellent results. The curve and the compound response factors met all of the method requirements. The overall precision was less than 5% RSD while the system showed an average recovery of 94%. When examining the expected analyte concentration to the extracted sand results, it was found that the average recovery was approximately 102%. Thus, the automated extraction performed extremely well. When comparing the three different matrices it was found that they all displayed similar recoveries, however the sand matrix did perform the best of the three as expected since sand tends not to absorb analytes as readily as other matrices. Finally, the ability to control the needle depth on extraction samples was a great benefit for the different matrices as the system exhibited no issues with needle clogging due to the higher needle depth when performing the potting soil extractions. As demonstrated from this study, the Centurion WS automated extraction capability would be an asset to any lab performing extractions.

Automated Sampling of Methanol Extractions 

<h4>Abstract</h4>Desorb flow control was developed in order to help manage the moisture associated with the four minute desorb time required for USEPA method 524.2. An added benefit to this process is the reduction in helium consumption when using this technique. This application will explain the patented process of Desorb Flow Control (DFC) (United States Patent Office numbers: 8062905, 7951609, 7803635) for Helium conservation and moisture control.&nbsp;<h4>Introduction</h4>Helium has been an essential component in environmental testing for years. Since Helium is an inert gas with a similar diffusion speed as Hydrogen, it is ideal for using as a carrier gas in Gas Chromatography. In recent years, however, there has been an increasing shortage of Helium, leading laboratories to come up with different ways of conservation.&nbsp;Desorb Flow Control was developed to assist laboratories routinely running for USEPA Method 524.2. Method 524.2 requires a four minute desorb and laboratories are reporting issues with water when using the long desorb time. By using DFC, labs are now able to keep the required four minute desorb time and control the amount of water transferred to the GC by decreasing the flow through the trap during desorb while maintaining the desired split ratio at the GC inlet. Subsequently, DFC not only controls the amount of water transferred, but also decreases Helium consumption. See Figures 1 and 2.<img src="https://storage.googleapis.com/labrulez-bucket-strapi-h3hsga3/EST_Analytical_Figure_1_Traditional_GC_Flow_ebb2a6357c.jpg" alt="EST Analytical: Figure 1 - Traditional GC Flow" srcset="https://storage.googleapis.com/labrulez-bucket-strapi-h3hsga3/thumbnail_EST_Analytical_Figure_1_Traditional_GC_Flow_ebb2a6357c.jpg 245w," sizes="100vw" width="1106" height="553"><img src="https://storage.googleapis.com/labrulez-bucket-strapi-h3hsga3/EST_Analytical_Figure_2_GC_Flow_with_Encon_Evolution_using_DFC_5af219d179.jpg" alt="EST Analytical: Figure 2 - GC Flow with Encon Evolution using DFC" srcset="https://storage.googleapis.com/labrulez-bucket-strapi-h3hsga3/thumbnail_EST_Analytical_Figure_2_GC_Flow_with_Encon_Evolution_using_DFC_5af219d179.jpg 245w," sizes="100vw" width="1389" height="684"><blockquote>(NOTE: The Encon Evolution provides the increased flow after the trap during desorb at a set time in the desorb process.)&nbsp;</blockquote>The advent of more efficient purge and trap systems and more sensitive GC/MS systems has aided in laboratories’ production. However, water control is still an issue. Labs may pass an initial calibration curve, but as water builds up in the system, internal standard response drops over time, causing the laboratory to fail continuing calibration checks. In order to combat water, many labs use a high split rate. As a consequence, Helium consumption is much higher and sensitivity is decreased. Using DFC, labs can still achieve the moisture control required thus creating a more stable system and lowering Helium consumption by as much as 80%, depending on the experimental split rate. See Table 1. *The table below assumes a throughput of 72 samples per day.<img src="https://storage.googleapis.com/labrulez-bucket-strapi-h3hsga3/EST_Analytical_Table_1_Daily_Helium_Consumption_ee240f3668.jpg" alt="EST Analytical: Table 1 - Daily Helium Consumption" srcset="https://storage.googleapis.com/labrulez-bucket-strapi-h3hsga3/thumbnail_EST_Analytical_Table_1_Daily_Helium_Consumption_ee240f3668.jpg 245w," sizes="100vw" width="1454" height="323"><h4>Experimental</h4>The sampling system used for this study was the <a target="_blank" rel="noopener noreferrer" href="https://gcms.labrulez.com/products/2160">EST Analytical Encon Evolution concentrator</a> and the <a target="_blank" rel="noopener noreferrer" href="https://gcms.labrulez.com/products/2159">Centurion WS autosampler</a>. The concentrator was affixed with a Vocarb 3000 trap and connected to an <a target="_blank" rel="noopener noreferrer" href="https://gcms.labrulez.com/library?mainauthorItems=10&amp;search=7890A">Agilent 7890A GC</a> and <a target="_blank" rel="noopener noreferrer" href="https://gcms.labrulez.com/library?mainauthorItems=10&amp;search=5975C">5975C inert XL MS</a>. The GC was configured with a Restek Rxi-624 Sil MS 30m x 0.25mm x 1.4µm column. Two different split ratios were used for comparison in this study, a 40:1 split rate was used for the baseline data and a 10:1 split rate was used for the DFC data. Experimental parameters used for this analysis are listed below.<h5>Purge and Trap Parameters</h5><ul><li>Concentrator: EST Encon Evolution</li><li>Trap type: Vocarb 3000</li><li>Valve oven temperature: 150 °C</li><li>Transfer line temperature: 150 °C</li><li>Trap temperature: 35 °C</li><li>Moisture Reduction Trap (MoRT) temperature: 39 °C</li><li>Purge time: 11 min</li><li>Purge flow: 40 mL/min</li><li>Dry purge Temp.: Ambient</li><li>Dry Purge Flow: 40mL/min</li><li>Dry Purge Time: 1.0 min &nbsp;</li><li>Desorb pressure Control: ON</li><li>Desorb Pressure: 13.5 psi</li><li>Desorb time: 4.0 min</li><li>Desorb preheat delay: 10 sec</li><li>Desorb temperature: 250 °C</li><li>MoRT bake temperature: 210 °C</li><li>Bake temperature: 260 °C</li><li>Sparge vessel bake temperature: 110 °C</li><li>Bake time: 8 min</li><li>Bake flow: 85 mL/min</li></ul><h5>Purge and Trap Auto-Sampler: EST Centurion WS</h5><ul><li>Sample Type: Water</li><li>Water Volume: 25ml</li><li>Internal Standard Vol.: 5 µl</li></ul><h5>GC/MS Parameters</h5><ul><li>System: <a target="_blank" rel="noopener noreferrer" href="https://gcms.labrulez.com/library?mainauthorItems=10&amp;search=7890%2F5975">Agilent 7890A/5975</a></li><li>Inlet: Split/splitless mode, 200 °C, 40:1 and 10:1 split ratio, 7.45 psi inlet head pressure</li><li>Column: Rxi-624Sil MS 30m x 0.25mm I.D. 1.4µm film thickness</li><li>Oven program: 40 °C (1.5 min) → ramp 8 °C/min → 100 °C, ramp 20 °C /min to 210 °C, hold for 1.25 min, 16.5 min run time</li><li>Column flow rate: 1 mL/min helium</li><li>Total flow: 13.8 and 43.8 mL/min</li><li>Source temperature: 230 °C</li><li>Quadrupole temperature: 150 °C</li><li>Transfer line temperature: 180 °C</li><li>Scan range: m/z 35–300, 3.12 scans/sec</li><li>Solvent delay: 1.0 min</li></ul>The USEPA Method 524.2 standards were acquired from AccuStandard. The linear ranges of the experiments were established by running eight point calibration curves from 0.5 to 100ppb. Table 4 displays curve linearity and compound response for the curves. Figure 3 displays chromatograms of the 20ppb calibration point with and without DFC. Finally, an experiment was run using Selective Ion Monitoring (SIM) of m/z 20 with and without DFC. This was done in order to show water control using D2O as the compound of interest so as not to SIM for water and overwhelm the MS. Figure 4 displays the results of this experiment.<img src="https://storage.googleapis.com/labrulez-bucket-strapi-h3hsga3/EST_Analytical_Table_4_Curve_Linearity_and_Compound_Response_Summary_7303558674.jpg" alt="EST Analytical: Table 4 - Curve Linearity and Compound Response Summary" srcset="https://storage.googleapis.com/labrulez-bucket-strapi-h3hsga3/thumbnail_EST_Analytical_Table_4_Curve_Linearity_and_Compound_Response_Summary_7303558674.jpg 107w," sizes="100vw" width="684" height="1003"><img src="https://storage.googleapis.com/labrulez-bucket-strapi-h3hsga3/EST_Analytical_Figure_3_20ppb_Chromatograms_With_and_Without_DFC_bebdb4c00f.jpg" alt="EST Analytical: Figure 3 - 20ppb Chromatograms With and Without DFC" srcset="https://storage.googleapis.com/labrulez-bucket-strapi-h3hsga3/thumbnail_EST_Analytical_Figure_3_20ppb_Chromatograms_With_and_Without_DFC_bebdb4c00f.jpg 245w," sizes="100vw" width="1383" height="518"><img src="https://storage.googleapis.com/labrulez-bucket-strapi-h3hsga3/EST_Analytical_Figure_4_Overlay_of_D2_O_mz_20_With_and_Without_DFC_701bb4011c.jpg" alt="EST Analytical: Figure 4 - Overlay of D2O mz 20 With and Without DFC" srcset="https://storage.googleapis.com/labrulez-bucket-strapi-h3hsga3/thumbnail_EST_Analytical_Figure_4_Overlay_of_D2_O_mz_20_With_and_Without_DFC_701bb4011c.jpg 143w," sizes="100vw" width="939" height="1026"><h4>Conclusions</h4>The results of this study show the patented Desorb Flow Control is an exceptional tool for conserving helium and creating a more stable system. The option of maintaining the desired split ratio at the GC inlet while decreasing the flow through the trap during desorb provides sensitivity while controlling the amount of moisture being sent onto the GC column. Furthermore, the split rate during the GC/MS run time is substantially lower than during the desorb time. Laboratories can have the advantage of running a higher split rate during the desorb process then maintaining a lower split during the rest of the GC/MS separation and analysis, thus providing laboratories with up to an 80% reduction in GC/MS helium use.

Benefits of Using Desorb Flow Control with the Encon Evolution

For more than 30 years, oxygenated compounds have been added to gasoline. The use of oxygenates provides two primary benefits: a reduction in pollution caused by vehicle emissions, as oxygenated gasoline burns more efficiently, and an improvement in overall engine performance.However, the prolonged use of oxygenated compounds has also led to environmental concerns. Increased contamination of groundwater has been observed, primarily due to leaks from underground storage tanks, allowing oxygenates to migrate into soil and water. In addition, because these compounds are highly soluble in water, analytical methods must be carefully optimized to achieve adequate detection limits.<h4>Discussion</h4>This application note investigates purge-and-trap experimental conditions to determine the most efficient and accurate approach for purging highly soluble fuel oxygenates. The study focuses on evaluating the effects of sample volume and purge temperature on analytical performance.The parameters examined include purge volumes of 5 mL, 10 mL, and 25 mL, as well as purge temperatures at room temperature and 60 °C. Experimental results were compared in terms of calibration range, linearity, method detection limits (MDLs), and compound response.A key feature of this study is the use of the EST Encon Evolution purge-and-trap concentrator, which provides enhanced control over moisture introduction into the GC system. Unlike conventional concentrators, the Encon Evolution employs an 8-port valve design that transfers analytes directly from the analytical trap to the GC via the transfer line, while excluding the Moisture Reduction Trap (MoRT) from the desorption pathway. This design is particularly advantageous when operating at elevated purge temperatures, as was required in this study. Flow paths for purge and desorption are illustrated in Figures 1 and 2.<img src="https://storage.googleapis.com/labrulez-bucket-strapi-h3hsga3/EST_Analytical_Purge_and_Desrob_Flow_Path_f7c9fec3a8.jpg" alt="EST Analytical: Figure 1 &amp; 2: Purge and Desrob Flow Path" srcset="https://storage.googleapis.com/labrulez-bucket-strapi-h3hsga3/thumbnail_EST_Analytical_Purge_and_Desrob_Flow_Path_f7c9fec3a8.jpg 245w," sizes="100vw" width="1141" height="568"><h4>Experimental</h4><h5>Instrumentation</h5>The sampling and concentration system consisted of an <a target="_blank" rel="noopener noreferrer" href="https://gcms.labrulez.com/products/2159">EST Analytical Centurion WS autosampler</a> coupled to an <a target="_blank" rel="noopener noreferrer" href="https://gcms.labrulez.com/products/2160">EST Encon Evolution purge-and-trap concentrator</a>. Experiments were conducted in water mode.The concentrator was configured with a VOCARB 3000 trap and interfaced to an <a target="_blank" rel="noopener noreferrer" href="https://gcms.labrulez.com/library?mainauthorItems=10&amp;search=7890A">Agilent 7890A gas chromatograph</a> equipped with a <a target="_blank" rel="noopener noreferrer" href="https://gcms.labrulez.com/library?mainauthorItems=10&amp;search=5975C">5975 inert XL mass spectrometer</a>. GC/MS operating parameters were selected to support EPA Method 8260 analysis.<h5>Purge and Trap Parameters</h5><ul><li>Concentrator: EST Encon Evolution</li><li>Trap type: Vocarb 3000</li><li>Valve oven temperature: 150 °C</li><li>Transfer line temperature: 150 °C</li><li>Trap temperature: 35 °C</li><li>Moisture Reduction Trap (MoRT) temperature: 39 °C</li><li>Purge time: 11 min</li><li>Purge flow: 40 mL/min</li><li>Dry purge Temp.: Ambient</li><li>Dry Purge Flow: 40mL/min</li><li>Dry Purge Time: 1.0 min &nbsp;</li><li>Desorb pressure Control: ON</li><li>Desorb Pressure: 12 psi</li><li>Desorb time: 1.0 min</li><li>Desorb temperature: 250 °C</li><li>MoRT bake temperature: 150 °C</li><li>Bake temperature: 265 °C</li><li>Sparge vessel bake temperature: 130 °C</li><li>Bake time: 8 min</li><li>Bake flow: 40 mL/min</li></ul><h5>GC/MS Parameters</h5><ul><li>System: <a target="_blank" rel="noopener noreferrer" href="https://gcms.labrulez.com/library?mainauthorItems=10&amp;search=7890%2F5975">Agilent 7890A/5975</a></li><li>Inlet: Split/splitless mode, 200 °C, 40:1 split ratio, 17.311 psi inlet head pressure</li><li>Column: Rtx-624 20m x 0.18mm I.D. 1µm film thickness</li><li>Oven program: 45 °C (1 min) → ramp 18 °C/min → 220 °C, hold for 0.3 min</li><li>Column flow rate: 0.8 mL/min helium</li><li>Total flow: 38.8 mL/min</li><li>Source temperature: 230 °C</li><li>Quadrupole temperature: 150 °C</li><li>Transfer line temperature: 180 °C</li><li>Scan range: m/z 35–265, 3.12 scans/sec</li><li>Solvent delay: 0.7 min</li></ul><h4>Standards and Calibration</h4>Oxygenate standards were obtained from Restek. The California oxygenate mixture included:<ul><li>Diisopropyl ether (DIPE)</li><li>Ethyl tert-butyl ether (ETBE)</li><li>tert-Amyl methyl ether (TAME)</li><li>tert-Butyl alcohol (TBA)</li><li>Methyl tert-butyl ether (MTBE)</li></ul>Most ether compounds were prepared at 2000 µg/mL, while TBA was prepared at 10,000 µg/mL. Ethanol standards were also obtained from Restek at 10,000 µg/mL.Calibration curves consisted of nine concentration levels, ranging from 0.5 to 200 ppb for ether compounds and 2.5 to 1000 ppb for TBA and ethanol. Method detection limits were determined using seven replicate injections at low calibration levels.<h4>Results and Discussion</h4>Evaluation of purge volume and purge temperature demonstrated that increasing sample volume resulted in improved compound response. Additionally, the use of a heated purge at 60 °C significantly enhanced the response of polar compounds, particularly ethanol and TBA, with ethanol response more than doubling under heated purge conditions.<img src="https://storage.googleapis.com/labrulez-bucket-strapi-h3hsga3/EST_Analytical_Table_3_Sample_Volume_and_Temperature_Experimental_Results_Summary_ace694091d.jpg" alt="EST Analytical: Table 3: Sample Volume and Temperature Experimental Results Summary" srcset="https://storage.googleapis.com/labrulez-bucket-strapi-h3hsga3/thumbnail_EST_Analytical_Table_3_Sample_Volume_and_Temperature_Experimental_Results_Summary_ace694091d.jpg 245w," sizes="100vw" width="1600" height="372">While larger sample volumes generally increased sensitivity, the 10 mL sample volume combined with a 60 °C purge temperature provided the best balance of sensitivity, linearity, and chromatographic performance. This condition also produced the most consistent linear calibration range, especially for ethanol, which is traditionally difficult to analyze using purge-and-trap techniques.Chromatograms comparing room-temperature purge and heated purge conditions (Figures 3 and 4) clearly illustrate the improved peak response and signal stability achieved with heated purging.<img src="https://storage.googleapis.com/labrulez-bucket-strapi-h3hsga3/EST_Analytical_Figure_3_50ppb_Chromatogram_with_Room_Temperature_Purge_8ea1cd120f.jpg" alt="EST Analytical: Figure 3: 50ppb Chromatogram with Room Temperature Purge" srcset="https://storage.googleapis.com/labrulez-bucket-strapi-h3hsga3/thumbnail_EST_Analytical_Figure_3_50ppb_Chromatogram_with_Room_Temperature_Purge_8ea1cd120f.jpg 245w," sizes="100vw" width="1548" height="688"><img src="https://storage.googleapis.com/labrulez-bucket-strapi-h3hsga3/EST_Analytical_Figure_4_50ppb_Chromatogram_with_60_C_Purge_5246c294e6.jpg" alt="EST Analytical: Figure 4: 50ppb Chromatogram with 60 °C Purge" srcset="https://storage.googleapis.com/labrulez-bucket-strapi-h3hsga3/thumbnail_EST_Analytical_Figure_4_50ppb_Chromatogram_with_60_C_Purge_5246c294e6.jpg 245w," sizes="100vw" width="1513" height="773"><h4>Full 8260 and California Oxygenate Analysis</h4>Following optimization, a full EPA Method 8260 calibration and validation was performed using the selected conditions (10 mL sample volume, 60 °C purge). Method performance was evaluated for linearity, precision (%RSD), recovery, and detection limits across the complete compound list.<img src="https://storage.googleapis.com/labrulez-bucket-strapi-h3hsga3/EST_Analytical_Table_4_Summary_of_8260_and_California_Oxygenate_Data_614adf67d6.jpg" alt="EST Analytical: Table 4: Summary of 8260 and California Oxygenate Data" srcset="https://storage.googleapis.com/labrulez-bucket-strapi-h3hsga3/thumbnail_EST_Analytical_Table_4_Summary_of_8260_and_California_Oxygenate_Data_614adf67d6.jpg 211w," sizes="100vw" width="1600" height="1187"><img src="https://storage.googleapis.com/labrulez-bucket-strapi-h3hsga3/EST_Analytical_Figure_5_50ppb_Standard_of_8260_and_Fuel_Oxygenates_5edd5bd337.jpg" alt="EST Analytical: Figure 5: 50ppb Standard of 8260 and Fuel Oxygenates" srcset="https://storage.googleapis.com/labrulez-bucket-strapi-h3hsga3/thumbnail_EST_Analytical_Figure_5_50ppb_Standard_of_8260_and_Fuel_Oxygenates_5edd5bd337.jpg 245w," sizes="100vw" width="1219" height="560"><img src="https://storage.googleapis.com/labrulez-bucket-strapi-h3hsga3/EST_Analytical_Figure_6_Extracted_Ion_Chromatogram_of_the_50_ppb_Standard_of_the_Fuel_Oxygenate_Compounds_in_the_8260_Mix_1e1684dbca.jpg" alt="EST Analytical: Figure 6: Extracted Ion Chromatogram of the 50 ppb Standard of the Fuel Oxygenate Compounds in the 8260 Mix" srcset="https://storage.googleapis.com/labrulez-bucket-strapi-h3hsga3/thumbnail_EST_Analytical_Figure_6_Extracted_Ion_Chromatogram_of_the_50_ppb_Standard_of_the_Fuel_Oxygenate_Compounds_in_the_8260_Mix_1e1684dbca.jpg 245w," sizes="100vw" width="1188" height="561">Results demonstrated that the system met or exceeded all method performance criteria. Recoveries and precision were within acceptable limits for both volatile organic compounds and oxygenates, confirming suitability for regulatory compliance applications.<h4>Conclusions</h4>Overall, fuel oxygenate compounds exhibited higher responses with increased sample volume, while purge temperature had the greatest impact on polar analytes, particularly ethanol and TBA. The heated purge at 60 °C, combined with a 10 mL sample volume, produced optimal linearity and sensitivity.The EST Encon Evolution purge-and-trap system, equipped with a Moisture Reduction Trap (MoRT), proved to be highly effective for fuel oxygenate analysis. The system demonstrated excellent moisture control, robust analyte transfer, and reliable performance for both California oxygenates and full EPA 8260 compound lists. In all cases, method performance met or exceeded regulatory requirements.

California Oxygenates and 8260

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