<p><strong>Concerns about injecting water into a GC system largely come from older column designs, where stationary phases were simply coated and could be affected by water exposure. Modern capillary columns are typically chemically bonded, which improves resistance to water injections and even supports water rinsing in many cases.</strong></p><p>One practical exception involves <strong>very polar polyethylene glycol </strong>(PEG / “wax”) phases. Because these phases strongly interact with water, repeated aqueous injections can allow water to accumulate and gradually shift selectivity. For many PEG-based columns, minimizing frequent water injections helps maintain consistent performance.</p><p>A separate—and often more important—issue is water’s<strong> very large vapor expansion in a hot inlet</strong>. If the vapor volume exceeds the inlet liner capacity, backflash can occur, sending sample vapor into cooler, unheated zones and increasing the risk of carryover. Using smaller injection volumes helps reduce this risk.</p><p>In workflows where water is the<strong> sample matrix </strong>(for example, volatile analysis), analytes may elute at relatively low oven temperatures while water and higher-boiling residues can linger. Periodic bake-off (high-temperature cleanup steps) is commonly used to restore column performance when water remains on the phase at low temperatures.</p><p>In summary, the biggest hesitation about water injections is rooted in legacy, coated column stories. With chemically bonded phases, the key considerations tend to be inlet expansion/backflash behavior, water retention on very polar phases, and routine maintenance practices like bake-out.</p><blockquote><h4><a target="_blank" rel="noopener noreferrer" href="https://gcms.labrulez.com/products/1571"><strong>Zebron ZB-WAX</strong><i><strong>PLUS</strong></i><strong> GC Columns</strong></a></h4><ul><li>100% aqueous stable, excellent for aqueous samples; bonded and solvent rinseable</li><li>Extremely inert for acidic compounds</li><li>Enhanced selectivity for low boiling solvents; high retention of alcohols and chlorinated solvents</li><li>Increased efficiency at 20&nbsp;°C</li></ul></blockquote>

Water in GC: Safe or Risky? Here’s What You Need to Know

<p><strong>Our Library never stops expanding. What are the most recent contributions to LabRulezGCMS Library in the week of 11th 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>poster by <strong>MDCW / William &amp; Mary</strong> and brochure by <strong>Thermo Fisher Scientific!</strong></p><h3><strong>1. MDCW / William &amp; Mary: Optimizing Solvent Selection and Data Reduction Workflows for GC×GC Fire Debris Analysis</strong></h3><ul><li>Poster</li><li><a target="_blank" rel="noopener noreferrer" href="https://gcms.labrulez.com/labrulez-bucket-strapi-h3hsga3/P_14_O_Brien_63304669ee.pdf"><strong>Full PDF for download</strong></a></li></ul><section><div><div><div><div><div><div><h5><strong>What are Ignitable Liquid Residues (ILRs)?&nbsp;</strong></h5><ul><li>Chemical remains of ignitable liquids (IL) (e.g., gasoline or diesel) that did not fully burn during a fire&nbsp;</li><li>ILRs are usually petroleum-based products and contain complex mixtures of volatile chemicals, like hydrocarbons&nbsp;</li></ul><h5><strong>Forensic Analysis of ILRs&nbsp;</strong></h5><ul><li>Collection of porous materials like wood from the fire’s point of origin&nbsp;</li><li>Must be stored in airtight containers to prevent volatile ILR from evaporation&nbsp;</li><li>Passive headspace extraction onto activate charcoal strips (ACS) is used to extract ILRs from debris, and dichloromethane (DCM) is used to extracts ILRs from charcoal strips&nbsp;</li><li>Emerging is the use of two-dimensional gas chromatography – time of fight - mass spectrometry (GC×GC-TOFMS), with higher separation and resolution</li><li>Resulting chromatograms presents a pattern of peaks which can be used to identified specific type of accelerant used&nbsp;</li></ul><h5><strong>Chemometrics&nbsp;</strong></h5><ul><li>The discipline that focuses on the application of statistical and mathematical methods to analyze chemical data and extract meaningful information (Bovens, 2019)&nbsp;</li><li>Helps make sense of large datasets from analytical instruments, find pattens, and classify samples</li></ul><h4><strong>Methods</strong></h4><h5><strong>Analytical Instrumentation&nbsp;</strong></h5><ul><li>LECO corporation <a target="_blank" rel="noopener noreferrer" href="https://gcms.labrulez.com/products/1097"><strong>BTX4D GC×GC-TOFMS</strong></a> with <a target="_blank" rel="noopener noreferrer" href="https://gcms.labrulez.com/products/1289"><strong>Paradigm Shift reverse fill-flush (RFF) flow modulator</strong></a></li></ul><h5><strong>Software&nbsp;</strong></h5><ul><li><a target="_blank" rel="noopener noreferrer" href="https://gcms.labrulez.com/products/1873"><strong>ChromaTOF Sync 2D</strong></a> (LECO corporation)&nbsp;</li><li>R Statistical Software</li></ul><h4><strong>Conclusions</strong></h4><p>This study demonstrated that the use of chemometrics can be integrated into a data processing workflow to better understand data sets and create a streamlined process. Using UMAP, patterns identified that were not originally seen in PCA lead to the preferred solvents of ILR extraction being hexane and methanol. Since UMAP allowed visualization of local and global structures, groupings of gasoline samples allowed for better analysis of solvent effect.</p><h3><strong>2. Shimadzu: Multiresidue Pesticides Analysis in Solvent Extract of Annatto (Natural Color Additive) Using </strong><a target="_blank" rel="noopener noreferrer" href="https://gcms.labrulez.com/library?mainauthorItems=1&amp;search=GCMS-TQ8050+NX"><strong>GCMSTQ8050 NX</strong></a></h3><ul><li>Application note</li><li><a target="_blank" rel="noopener noreferrer" href="https://gcms.labrulez.com/labrulez-bucket-strapi-h3hsga3/an_06_sip_gc_043_en_95576a9ac4.pdf"><strong>Full PDF for download</strong></a></li></ul><h5><strong>User Benefits</strong></h5><ul><li>&nbsp;Accurate and reproducible trace level quantitation of pesticides in highly pigmented complex matrix using Ultra-fast GCMSTQ8050 NX and QuEChERS extraction</li><li>Single-laboratory partial validated method for LOQ determination meeting regulatory guidelines</li><li>Ease of instrumental method optimization using GCMS Smart Pesticides Database Ver.2 from Shimadzu Corporation</li></ul><p>Annatto is an orange-red condiment and food colorant derived from the seeds of the achiote tree (Bixa Orellana) (Fig. 1). It is often used to impart a yellow to red-orange color to foods, but sometimes also for its flavor and aroma. Similar effects can be obtained by extracting some of the color and flavor principles from the seeds, which are then added to the food. Annatto and its extracts are now widely used in an artisanal or industrial scale as a coloring agent in many processed food products, such as cheeses, butter, baked goods, potatoes, snack foods, breakfast cereals, smoked fish etc. In these uses, Annatto is a natural alternative to synthetic food coloring compounds.&nbsp;</p><p>Owing to its large culinary uses and other diverse applications, use of chemical pesticides for its production in large quantities is imperative. Dye extraction process may result in concentration of pesticides and in turn contribute to adverse impact on human health when incorporated in various preparations. Hence quantitation of residual pesticides in Annatto extract becomes very important. As the oleoresin is a complex matrix, it is required to develop a rugged, sensitive and efficient method for extraction of residual pesticide and its analysis.&nbsp;</p><p>This study reports a highly sensitive method for simultaneous quantification of multiple pesticides in highly pigmented complex matrix of Annatto using modified QuEChERS[1] with triple quadrupole gas chromatography (GC-MS/MS) system.</p><h4><strong>Materials and Methods</strong></h4><p>For this study, customized reference standard mixture of most commonly observed pesticides in Annatto seeds was procured from Restek Corporation.</p><p>The calibration standards were analyzed from 0.5 to 1000 μg/L. Linearity was plotted by external standard method and using weighted regression of 1/C2. Sample was spiked at 3 levels i.e., 10, 25 and 100 μg/kg. Recovery samples were prepared in 6 replicates at each level. <a target="_blank" rel="noopener noreferrer" href="https://gcms.labrulez.com/library?mainauthorItems=1&amp;search=GCMS-TQ8050+NX"><strong>GCMS-TQ8050 NX</strong></a> (Fig. 2), manufactured by Shimadzu Corporation Japan, was used for quantitation. LabSolutions InsightTM was used for data processing, which helped in evaluating validation parameters with ease.</p><h4><strong>Conclusion</strong></h4><p>This study shows that the modified QuEChERS method combined with GC-MS/MS system is a reliable and efficient tool to quantify residual pesticides in Annatto extract sample. Although Annatto extract is a highly pigmented complex matrix, the modified QuEChERS method significantly reduces interference. Also, extremely sensitive Shimadzu GC-MS/MS allows trace level detection even after multifold dilution of sample. This helps in reducing contamination and enhancing ruggednessresulting in reproducible detection of analytes.</p><h3><strong>3. Thermo Fisher Scientific: Sentinel PRO 710 environmental mass spectrometer Precise real time gas analyzer for toxic volatile organic compounds</strong></h3><ul><li>Product specification</li><li><a target="_blank" rel="noopener noreferrer" href="https://gcms.labrulez.com/labrulez-bucket-strapi-h3hsga3/sentinel_pro_710_spec_sheet_en_886523bfc2.pdf"><strong>Full PDF for download</strong></a></li></ul><p>The <a target="_blank" rel="noopener noreferrer" href="https://gcms.labrulez.com/library?mainauthorItems=3&amp;search=Sentinel+PRO"><strong>Thermo Scientific™ Sentinel PRO Environmental Mass Spectrometer </strong></a>is a highly reliable and versatile gas analyzer ideal for reporting the presence of toxic VOCs from fugitive emissions in industrial settings to ensure worker safety.</p><h4><strong>Fugitive emissions of toxic VOCs&nbsp;</strong></h4><p>Wherever there is potential danger for fugitive emissions of toxic organic vapors from a chemical production unit, regulating authorities often require plants to keep records of ambient vapor concentrations to protect workers from exposure. Various forms of capture include evacuated vessels, organic vapor monitors, or purge and trap devices, all of which require samples to be sent for analysis. Alternatively, electrochemical sensors or open path FT-IR spectroscopy can provide more immediate results. However, none of these technologies are capable of providing the spatial and temporal resolution required to qualify as actionable information.&nbsp;</p><h4><strong>Analytical platform&nbsp;</strong></h4><p>The primary feature of the Sentinel PRO mass spectrometer is the magnetic sector analyzer. This field-proven technology has demonstrated the strongest performance for industrial on-line gas analysis. Magnetic sector technology offers precision, accuracy, long intervals between calibrations. The new touchscreen interface further enhances usability, providing intuitive in-person operation, simplified maintenance, and real-time data viewing. Multi-role user permissions ensure security and control allowing operators to customize settings based on their specific needs.&nbsp;</p><h4><strong>Comprehensive data collection&nbsp;</strong></h4><p>With speed and precision, the Sentinel PRO analyzer monitors all the critical areas for short-term exposure levels of toxic VOCs, and also provides accurate and time-weighted average exposure data. With a high number of sample points available, many can be located close to potential leak points such as valve stems, etc., enabling leak detection and correction before any toxic hazard is created.&nbsp;</p><h4><strong>Membrane inlet mass spectrometry&nbsp;</strong></h4><p>The analyzer is fitted with a membrane inlet to reduce the pressure of the sample air from atmospheric to the working pressure of the enclosed ion source. This allows a method of sample introduction that greatly enhances the system’s sensitivity to VOCs. Since the membrane is more permeable to VOCs than to major air gases, it provides enrichment by several orders of magnitude, enabling detection as low as 5 ppb (species dependent) permits easy membrane replacement during annual routine maintenance to minimize downtime and increase productivity.</p></div></div></div></div></div></div></section>

News from LabRulezGCMS Library - Week 20, 2026

<p><strong>🎤Lindsay Repka&nbsp;</strong></p><p><strong>Lindsay Repka is a chemistry professor at Middlebury College whose research explores photoredox chemistry, catalyst stability, and visible-light-driven transformations. Her lab emphasizes both mechanistic insight and hands-on student training in advanced analytical instrumentation.</strong></p><p>In this episode of Concentrating on Chromatography, we sit down with Lindsay Repka to discuss how LC-MS and GC-MS transformed her lab’s approach to photoredox chemistry.</p><p>What began as a project to develop a visible-light photocrosslinking handle unexpectedly led to a major discovery: the solvent (DMF) was reacting with the photocatalyst itself. Using high-resolution LC-MS, Lindsay’s team observed multiple solvent adducts forming — sometimes with complete catalyst consumption. That discovery reshaped their research direction.</p><p>This episode is a rare deep dive into both LC-MS and GC-MS within the same research project, showing how chromatography-driven insight can turn unexpected degradation into productive new reactivity.</p><p><strong>If you work in:</strong></p><ul><li>Photoredox chemistry</li><li>Reaction optimization</li><li>Mass spectrometry method development</li><li>Catalyst screening</li><li>Academic synthetic chemistry</li></ul><p>…this conversation will resonate.</p><h4><strong>Key Topics Covered</strong></h4><ul><li>Photocatalyst stability in DMF, DCE, and MeCN</li><li>Demethylation under mild visible-light conditions</li><li>High-resolution Q-TOF LC-MS quantitation</li><li>Internal standard methodology in GC-MS</li><li>Signal-to-noise improvement using extracted ion chromatograms</li><li>Reaction reproducibility and quality control strategy</li></ul><h3><strong>Video Transcription</strong></h3><p>In this interview, Lindsay Repka discusses the role of photoredox chemistry in method development, photocrosslinking, solvent activation, catalyst stability, and the use of LC-MS and GC-MS to understand reaction pathways.</p><h4><strong>What is photoredox chemistry?</strong></h4><p>Photoredox chemistry uses light to activate a photocatalyst, which can either donate or accept an electron from a substrate. This generates radical species that can undergo new types of reactivity.</p><p>Repka explains that one of the key advantages of photoredox chemistry is its ability to operate under mild conditions, often using visible light. This makes it attractive for sensitive molecules and biological systems, including potential applications in drug release, live-cell chemistry, and drug development.</p><h4><strong>Photocrosslinking and drug-target interactions</strong></h4><p>Repka’s group initially aimed to develop visible-light photocrosslinking methods to study drug interactions with biological targets. Photocrosslinking can covalently link a drug to its target, making it easier to identify the biological target of a compound.</p><p>Traditional photocrosslinking often uses UV light, but visible light offers milder and more biologically compatible conditions.</p><h4><strong>From photocrosslinking to solvent activation</strong></h4><p>The project shifted direction when the desired photocrosslinking reactions gave very low yields. Instead of reacting with amino acids as intended, the radical intermediate mainly reacted with itself.</p><p>The team explored different solvents to stabilize the radical, but found that some solvents, such as DMF, were not inert. Instead, the solvent reacted with the photocatalyst or radical species, revealing unexpected solvent activation chemistry.</p><h4><strong>Why LC-MS was critical</strong></h4><p>LC-MS became essential because the reaction mixtures were too complex and low-yielding for NMR or GC-MS. High-resolution LC-MS allowed the team to detect minor products, identify photocatalyst modifications, and observe solvent addition products with high confidence.</p><p>Repka emphasizes that LC-MS was both a qualitative and quantitative tool. It was used quantitatively to measure how much photocatalyst remained after light exposure, and qualitatively to identify degradation products and new reactivity pathways.</p><h4><strong>Photocatalyst stability workflow</strong></h4><p>The team developed a systematic workflow to evaluate photocatalyst stability under light exposure. Because catalyst degradation was time-sensitive, reproducibility required strict control of experimental conditions.</p><p>Key steps included using a glove box, commercial deoxygenated solvents, accurate weighing on a microbalance, controlled light exposure in a photoreactor, and temperature control with a chiller. These precautions helped reduce day-to-day variability and enabled reproducible measurements of catalyst remaining.</p><h4><strong>Quantifying catalyst remaining by LC-MS</strong></h4><p>Calibration curves were prepared using pure photocatalyst solutions and LC-MS ion areas. The team worked in the nanomolar range to maintain linearity.</p><p>Instead of relying only on total ion chromatograms, they used extracted ion chromatograms (EICs) to improve signal-to-noise for the photocatalyst signal. Baseline subtraction was also applied to reduce noise and improve quantitation at low concentrations.</p><p>Calibration curves and quality control samples were prepared and measured on the same day as the reaction samples, because LC-MS signal intensity can vary significantly from day to day.</p><h4><strong>Why GC-MS was used later</strong></h4><p>For demethylation studies, the group moved to GC-MS because the substrates and products were small and volatile enough for gas chromatography. GC-MS was better suited for rapidly screening many reaction conditions, including different photocatalysts, solvents, and oxidants.</p><p>Instead of generating full calibration curves for every experiment, the team used an internal standard to streamline analysis and determine percent conversion based on relative response factors.</p><h4><strong>Practical lessons from the project</strong></h4><p>Repka highlights the importance of careful sample preparation, especially when working with very small quantities of photocatalysts. A high-quality microbalance, stable granite platform, antistatic tools, and aluminum weigh boats improved weighing accuracy and reproducibility.</p><p>She also argues that mass spectrometry should be a standard part of photoredox method development because it can reveal minor products, support reaction optimization, and provide insights that may be difficult or impossible to obtain by NMR alone.</p><h4><strong>Final perspective</strong></h4><p>Beyond the chemistry, Repka emphasizes the importance of student training and mentoring. For her, research is not only about discovering new reactivity but also about giving students practical experience, helping them develop independence, and preparing them for future scientific careers.</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><blockquote><h4><strong>Concentrating on Chromatography Podcast</strong></h4><p>Dive into the frontiers of chromatography, mass spectrometry, and sample preparation with host David Oliva. Each episode features candid conversations with leading researchers, industry innovators, and passionate scientists who are shaping the future of analytical chemistry. From decoding PFAS detection challenges to exploring the latest in AI-assisted liquid chromatography, this show uncovers practical workflows, sustainability breakthroughs, and the real-world impact of separation science. Whether you’re a chromatographer, lab professional, or researcher you'll discover inspiring content!</p><p>You can find <strong>Concentrating on Chromatography Podcast </strong>in podcast apps:</p><ul><li><a target="_blank" rel="noopener noreferrer" href="https://open.spotify.com/show/1wZg67rCjoGju4yhqxI3tL"><strong>Spotify</strong></a></li><li><a target="_blank" rel="noopener noreferrer" href="https://podcasts.apple.com/tz/podcast/concentrating-on-chromatography/id1788429185"><strong>Apple podcast</strong></a></li><li><a target="_blank" rel="noopener noreferrer" href="https://podscan.fm/podcasts/concentrating-on-chromatography"><strong>podscan</strong></a></li></ul><p>and on <a target="_blank" rel="noopener noreferrer" href="https://www.youtube.com/@ChromatographyTalk/videos"><strong>YouTube channel</strong></a></p></blockquote>

Using LC-MS & GC-MS to Decode Photoredox Catalyst Stability

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