EU Regulation 396/2005: Pesticide Residue Testing and the Critical Role of QuEChERS Evaporation in Food Safety

<p><strong>🎤 Presenter:</strong> <strong>Caleb Marx </strong>(University of Lethbridge)</p><p>💾 <a target="_blank" rel="noopener noreferrer" href="https://gcms.labrulez.com/paper/32847"><strong>PDF presentation</strong></a></p><h3><strong>Abstract</strong></h3><p><strong>Smoke from fires releases large quantities of hazardous chemicals into the atmosphere causing poor air quality at local, regional, and global scales. Due to the complexity of smoke emissions, the health impacts from inhalation and dermal exposure vary with fuel type and combustion conditions. Accurate emissions characterization data is critical for understanding health risks associated with smoke exposure. To date, smoke characterization has been predominately conducted utilizing filter extracts and standard GC-MS. This method has several limitations including lengthy extraction times, excessive use of toxic solvents, and cluttered chromatograms resulting in peak coelution. The use of </strong><a target="_blank" rel="noopener noreferrer" href="https://gcms.labrulez.com/library?instrumentationItems=8"><strong>thermal desorption (TD)</strong></a><strong> combined with two-dimensional gas chromatography offers an appealing alternative to traditional methods by improving recovery, eliminating solvent use, and enhancing chromatographic clarity through second dimension separation. However, limited work has been published optimizing these techniques for smoke emissions.</strong></p><p>This research sought to optimize sorbent bed selection and TD method parameters to allow non targeted analysis of smoke emissions. We explored the application of 6 unique sorbent bed combinations to optimize analyte retention of smoke compounds with varying polarity and volatility. Following sorbent selection, a design of experiment approach was applied to optimize the analytical desorption parameters (time, temperature, and flow) and conditioning methodology (time, temperature). The method was validated using smoke collected from lab-scale combustion chamber under controlled conditions. This study establishes a strong analytical foundation to improve our understanding of both primary and secondary smoke emissions, supporting more accurate risk assessment and informing public health and environmental policy.</p><h3><strong>Video Transcription</strong></h3><h4><strong>Thermal Desorption–GC×GC for Wildfire Smoke Analysis</strong></h4><p>Wildland fires are a major global source of atmospheric contamination. Beyond the direct destruction caused by flames, wildfire smoke releases large amounts of carbon and a complex mixture of airborne pollutants that can travel hundreds of kilometers and affect air quality far from the fire source.</p><p>Smoke can be viewed as a highly complex chemical mixture containing particulate matter, inorganic gases such as carbon dioxide, carbon monoxide and nitrogen oxides, and a broad range of volatile organic compounds (VOCs). Of particular analytical interest are compounds such as BTEX and polycyclic aromatic hydrocarbons (PAHs), which are relevant to both environmental and human health impacts.</p><p>A key challenge is that smoke composition changes as it moves through the atmosphere. Primary VOCs emitted directly from combustion can undergo oxidation and contribute to secondary organic aerosol formation, shifting material from the gas phase into the particulate phase. This means that smoke characterization should consider both freshly emitted compounds and the chemical changes that occur during atmospheric aging.</p><h4><strong>Limitations of Conventional Filter Sampling</strong></h4><p>Filter sampling is widely used for wildfire smoke studies and remains a valuable approach for particulate matter characterization. Filters can be extracted for organic analysis, digested for metals, or used to determine particulate loading and size distributions.</p><p>However, filter sampling does not adequately capture gas-phase organic compounds. This is a significant limitation when the goal is to characterize the full chemical profile of smoke emissions. Thermal desorption offers a complementary approach by enabling collection and analysis of volatile and semi-volatile organic compounds, including compounds present in the gas phase.</p><h4><strong>Thermal Desorption as a Sampling Strategy</strong></h4><p>Thermal desorption uses sorbent-packed tubes to trap VOCs from air samples. These tubes may contain one or more sorbent materials, allowing the method to be tailored to a target volatility range. Common sorbent types include porous polymers such as Tenax TA, graphitized carbon black and carbon molecular sieves.</p><p>Sorbent selection is critical. Stronger sorbents can retain more volatile analytes, but they may also retain more water, which can complicate analysis. Multi-bed tubes can broaden the analyte range, but require careful optimization to balance analyte recovery, water retention and desorption efficiency.</p><p>After sampling, the thermal desorption tube is transferred to the laboratory, where heat and carrier gas release the trapped analytes into the analytical system.</p><h4><strong>Why GC×GC Matters for Smoke</strong></h4><p>Because wildfire smoke is chemically complex, comprehensive two-dimensional gas chromatography (GC×GC) is especially useful. In this work, thermal desorption was coupled with GC×GC using a non-polar first-dimension column, a semi-polar second-dimension column and flow modulation.</p><p>This configuration provides enhanced separation capacity for complex smoke samples, where one-dimensional GC may struggle with coelution. In the wildfire smoke application, each sample produced an average of approximately 166 unique peaks, highlighting the complexity of the matrix.</p><h4><strong>Method Optimization</strong></h4><p>The study optimized thermal desorption for smoke analysis through four main experiments:</p><ul><li>sorbent bed selection</li><li>tube conditioning optimization</li><li>desorption parameter optimization</li><li>long-term storage stability</li></ul><p>A combined liquid standard mixture was used, containing 41 target compounds across a broad range of retention indices, hydrophobicities and Henry’s law constants. Liquid standards were introduced onto thermal desorption tubes using a nitrogen stream, allowing controlled evaluation of recovery, linearity and detection limits.</p><h4><strong>Sorbent Selection and Concentration Effects</strong></h4><p>Six sorbent tube configurations were compared, including in-house and commercially packed tubes. Performance was evaluated using recovery, linearity and limits of detection.</p><p>An important observation was that sorbent performance depended on analyte concentration. At higher concentration, a Tenax TA/Carbopack X configuration showed strong retention performance across the target analytes. At lower concentration, a triple-bed tube performed better.</p><p>This concentration-dependent behavior is important for field applications. Urban air sampling, where analyte levels may be low, may benefit from a different sorbent strategy than wildfire smoke sampling, where concentrations can be much higher.</p><h4><strong>Conditioning and Desorption Optimization</strong></h4><p>Tube conditioning is the cleaning step that allows thermal desorption tubes to be reused. The study showed that conditioning temperature and time could be reduced below commonly recommended conditions while still removing retained analytes effectively. This can save laboratory time and may extend sorbent lifetime.</p><p>Desorption parameters, including time, temperature and trap flow, were also optimized. The results suggested that desorption conditions could be reduced without significantly affecting peak area. This is beneficial because lower desorption stress can preserve sorbent performance, reduce gas consumption and shorten analytical runs.</p><p>Some concentration-dependent effects were observed at the high and low ends of the calibration range, suggesting that further study of desorption conditions across concentration ranges may be valuable.</p><h4><strong>Storage Stability</strong></h4><p>A 35-day storage stability experiment was conducted across eight sampling intervals. No significant analyte loss was observed over the full storage period. This is a practically important finding for field sampling campaigns, where samples may need to be transported or stored before analysis.</p><h4><strong>Application to Wildfire Smoke</strong></h4><p>The optimized method was applied to smoke generated from combustion of white spruce in a controlled setup. Approximately one liter of emitted smoke was collected and analyzed by TD–GC×GC.</p><p>The method detected a complex chromatographic profile, with most peaks falling in the C6–C14 range. Of the 41 standard compounds, 19 were identified in the smoke samples, including PAHs and BTEX compounds. These analytes fell within the established linear range, supporting the suitability of the method for targeted and broader smoke characterization.</p><h4><strong>Conclusion</strong></h4><p>Thermal desorption coupled with GC×GC offers a powerful approach for wildfire smoke analysis, particularly because it can address gas-phase organic compounds that are not captured effectively by conventional filter sampling.</p><p>The work demonstrates that sorbent selection, conditioning, desorption parameters and storage stability all play important roles in method performance. The observed concentration dependence of sorbent behavior is especially relevant for adapting methods to different sampling scenarios, from urban air monitoring to high-concentration wildfire smoke studies.</p><p>Overall, optimized TD–GC×GC provides a robust platform for characterizing complex smoke emissions and improving understanding of how wildfire-derived organic compounds affect air quality and environmental exposure.</p><blockquote><p><strong>This text has been automatically transcribed from a video presentation using AI technology. It may contain inaccuracies and is not guaranteed to be 100% correct.</strong></p></blockquote>

Selection, Optimization, and Validation of Thermal Desorption for analysis of VOCs and PAHs in Combustion Emissions (Caleb Marx, MDCW 2026)

<p><strong>Our Library never stops expanding. What are the most recent contributions to LabRulezGCMS Library in the week of 4th May 2026? Check out new documents from the field of the gas phase, especially GC and GC/MS techniques!</strong></p><blockquote><p><span style="font-size:20px;">👉 </span><a target="_blank" rel="noopener noreferrer" href="https://gcms.labrulez.com/library"><span style="font-size:20px;"><strong>SEARCH THE LARGEST REPOSITORY OF DOCUMENTS ABOUT GCMS AND RELATED TECHNIQUES</strong></span></a></p></blockquote><blockquote><p><strong>👉 Need info about different analytical techniques?</strong> Peek into <a target="_blank" rel="noopener noreferrer" href="https://lcms.labrulez.com/library"><strong>LabRulezLCMS</strong></a> or <a target="_blank" rel="noopener noreferrer" href="https://icpms.labrulez.com/library"><strong>LabRulezICPMS</strong></a> libraries.</p></blockquote><p>This week we bring you application note by<strong> Shimadzu, </strong>presentation by <strong>MDCW / JEOL</strong> and technical note by <strong>Thermo Fisher Scientific!</strong></p><h3><strong>1. MDCW / JEOL: Flow-Modulated GCxGC-QMS Analysis Without Splitting Off the GC Flow</strong></h3><ul><li>Presentation</li><li><a target="_blank" rel="noopener noreferrer" href="https://gcms.labrulez.com/labrulez-bucket-strapi-h3hsga3/O_16_Jensen_11e29d5022.pdf"><strong>Full PDF for download</strong></a></li></ul><section><div><div><div><div><div><div><p>This presentation by Kirk Jensen (JEOL USA) explores the feasibility of performing <strong>flow-modulated comprehensive two-dimensional gas chromatography (GC×GC) coupled with quadrupole mass spectrometry (QMS)</strong> without splitting the GC flow, which is traditionally required to protect MS systems from high carrier gas flows. The core concept builds on GC×GC, where compounds are separated using a primary and secondary column connected via a modulator, significantly increasing separation power compared to one-dimensional GC. The presentation contrasts <strong>thermal modulation</strong> (offering sharper peaks and higher theoretical sensitivity but requiring cryogenic cooling) with <strong>flow modulation</strong>, which avoids cryogens, handles volatile analytes well, and is more flexible, but typically demands higher gas flows that standard MS systems cannot tolerate .</p><p>To address this limitation, the study utilizes the <a target="_blank" rel="noopener noreferrer" href="https://gcms.labrulez.com/library?manufacturerItems=24&amp;search=JMS-Q1600GC"><strong>JEOL JMS-Q1600GC</strong></a><strong> UltraQuad quadrupole GC-MS system</strong>, which can accept unusually high carrier gas flows (up to ~20 mL/min), enabling direct coupling with a <strong>SepSolve INSIGHT flow modulator</strong> without splitting the effluent . The analytical setup includes dual GC columns (e.g., Zebron ZB-5MSplus for the first dimension and BPX50 for the second), high secondary flow rates (~25 mL/min), and electron ionization (EI) MS detection. Additional system components include optional FID detection, bleed line control, and ChromeSpace software for data processing . This configuration allows full analyte transfer into the MS, eliminating the need for flow splitting and potentially improving detection efficiency.</p><p>Experimental results demonstrate the applicability of this approach to complex mixtures, including a <strong>pesticide mixture containing over 200 compounds</strong> and real-world samples such as perfumes and fuels. The GC×GC-MS system produced detailed two-dimensional chromatograms with high spectral quality, enabling the correct identification of approximately 120 compounds despite relatively moderate spectral match factors . Comparisons at different flow rates (e.g., 25 vs. 50 mL/min) showed that spectral integrity and compound identification remain robust, indicating that higher flow operation does not significantly compromise MS performance.</p><p>In conclusion, the work demonstrates that <strong>flow-modulated GC×GC-QMS without flow splitting is feasible</strong>, provided that the MS system can tolerate high carrier gas flows. While further optimization is needed (e.g., column selection, inlet pressure, and separation conditions), the approach offers a practical alternative to thermal modulation by eliminating cryogens and simplifying operation. Future work will focus on improving sensitivity, optimizing separations, and exploring alternative carrier gases such as hydrogen to reduce costs and expand applicability</p></div></div></div></div></div></div></section><h3><strong>2. Shimadzu: Detailed Hydrocarbon Analysis by Nexis GC-2030 Using ASTM D6730</strong></h3><ul><li>Application note</li><li><a target="_blank" rel="noopener noreferrer" href="https://gcms.labrulez.com/labrulez-bucket-strapi-h3hsga3/an_01_00863_en_eb633bc741.pdf"><strong>Full PDF for download</strong></a></li></ul><h5><strong>User Benefits</strong></h5><ul><li>Detailed compositional analysis of gasoline in accordance with ASTM D6730 is feasible using the Nexis GC-2030.&nbsp;</li><li>By employing PONAsolution, a PONA/DHA analysis software, laborious identification tasks can be reduced, and quantitation calculations and report generation can be performed automatically.</li></ul><p>ASTM D6730 specifies the analysis of hydrocarbons in gasoline and oxygenates such as ethanol, methyl tert-butyl ether (MTBE), and ethyl tert-butyl ether (ETBE) over a boiling point range up to 225 ̊C. Identification and quantification of individual compounds in gasoline are critically important for refinery process control and product quality assurance. In this application news, we report compositional analysis of gasoline conforming to ASTM D6730 using the <a target="_blank" rel="noopener noreferrer" href="https://gcms.labrulez.com/library?mainauthorItems=1&amp;search=Nexis+GC-2030"><strong>Nexis GC-2030 gas chromatograph</strong></a>. Gasoline typically comprises over 100 hydrocarbons, making identification tasks highly complex; however, PONAsolution, a PONA/DHA analysissoftware,simplifies this process.</p><h4><strong>PONAsolution</strong></h4><p>PONAsolution Ver.6 provides retention index libraries for each relevant standard (ASTM D6730, D6729, D5134, D6733). Identification of n-alkanes automatically corrects the retention times of the remaining several hundred components, thus streamlining the identification process. When only a specific retention region requires adjustment, the two-point identification function is useful (Fig. 1). In the two-point identification procedure, reference and sample chromatograms are compared while assigning corresponding peaks. First, click on an identified component mark in the reference data (Fig. 1, a), then click the matching sample peak (Fig. 1, b). Repeat this for a second pair of peaks. The retention times of components between these two anchor points are then automatically corrected.</p><h4><strong>Conclusion</strong></h4><p>Compositional analysis of gasoline in accordance with ASTM D6730 was performed. The combination of SH PONA Tuning Column and SH-1 PONA main column enabled separation of compounds with closely spaced retention times. Moreover, use of PONAsolution software greatly simplifies complex identification tasks.</p><h3><strong>3. Thermo Fisher Scientific: Fiber optic probes add flexibility to Raman chemical analysis</strong></h3><ul><li>Technical note</li><li><a target="_blank" rel="noopener noreferrer" href="https://gcms.labrulez.com/labrulez-bucket-strapi-h3hsga3/drx3_flex_tech_note_tn54708_bebb56b870.pdf"><strong>Full PDF for download</strong></a></li></ul><p>Fourier Transform Infrared Spectroscopy (FTIR) and Raman Spectroscopy are non-destructive analytical techniques that rely on the interaction of electromagnetic radiation with molecular vibrations to provide information about the chemical composition and structure of a sample. Despite their similarities, there are some distinct differences between the two techniques. In principle, FTIR is based on the absorption of infrared radiation by molecules and measures changes in dipole moment during molecular vibrations. Raman spectroscopy, on the other hand, is based on the inelastic scattering of monochromatic light and measures changes in polarizability during molecular vibrations.&nbsp;</p><p>When applied to bulk chemical analysis, both FTIR and Raman spectroscopy can be used to analyze solids, liquids, and gases, but the nature of Raman spectroscopy lends some unique sampling advantages. Additionally, Raman often requires little to no sample preparation. Presented herein are application examples that highlight some of the sampling advantages of Raman spectroscopy. All the spectral data in this technical note were collected using a <a target="_blank" rel="noopener noreferrer" href="https://gcms.labrulez.com/products/2238"><strong>Thermo Scientific™ DXR3 Flex Raman Spectrometer</strong></a> equipped with a fiber optic probe. (Fiber optics are readily available for Raman spectroscopy because of the use of visible and NIR light and do not require the exotic materials associated with FTIR fiber optics.) Preliminary tests for all samples were carried out using both 532 nm and 785 nm excitations, and it was determined that the 785 nm laser set gave an overall better balance between fluorescence and Raman scattering efficiency.</p><h4><strong>Summary&nbsp;</strong></h4><p>In this technical note, the analyses of a variety of samples by Raman spectroscopy are demonstrated. All samples were analyzed without sample preparation.&nbsp;</p><ul><li>Precise and localized analysis at the focal point of the Raman-exciting laser allows sampling through glass bottles, blister packaging and plastic containers, which eliminates possible cross contamination and analyst exposure to hazardous materials. The contributions from the packaging and containers depend on the type of container material, the container thickness, and the materials’ chemical compositional complexity, but these contributions can be readily subtracted out when needed.&nbsp;</li><li>Water is a weak Raman scatterer. Raman therefore has reduced water sensitivity, making it a preferred technique for aqueous solution analysis over FTIR. As demonstrated in the analysis of an energy drink, the Raman bands from water can be subtracted from the spectrum of the aqueous solution, leading to the identification of the components of the solution.&nbsp;</li><li>Raman spectroscopy is well suited for the analysis of inorganic materials, especially in identifying the crystal phases and polymorphs, as demonstrated by the analyses of minerals and pigments in a painting.&nbsp;</li><li>Fiber optic probes provide flexibility and ease of maneuverability. This is particularly advantageous when analyzing samples that are difficult to access or manipulate, such as large containers, geological samples and paintings</li></ul><p>The DXR3 Flex has multiple sampling options available. A properly configured fiber-optic probe is arguably the most versatile accessory for the analysis of bulk solids and liquids. The advantages, both from those inherent to Raman spectroscopy and those resulting from the use of fiber optic probe, provide opportunities for a wide variety of different applications when using the DXR3 Flex Raman Spectrometer.</p>

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News from LabRulezGCMS Library - Week 19, 2026

Selection, Optimization, and Validation of Thermal Desorption for analysis of VOCs and PAHs in Combustion Emissions (Caleb Marx, MDCW 2026)