<p><strong>🎤 Presenter:</strong> <strong>Darshil Patel </strong>(University of North Dakota)</p><p>💾 <a target="_blank" rel="noopener noreferrer" href="https://gcms.labrulez.com/paper/32781"><strong>PDF presentation</strong></a></p><h3><strong>Abstract</strong></h3><p><strong>Flow-modulated two-dimensional gas chromatography (GCxGC) is an excellent solution for low-boiling point compounds that are difficult to separate by thermal modulation without cryogens. Pairing a quadrupole mass spectrometer (QMS) with GCxGC can offer better dynamic range, increased sensitivity, and lower cost to GCxGC applications, however, many MS instruments can not accept the high flow rate coming from flow-modulated GCxGC.</strong></p><p>In this study, a flow modulator was installed in a QMS system designed to accept high GC flow rates, and tested using perfume and pesticide applications. Results detailing the sensitivity and effectiveness of the QMS system with high GCxGC flow input will be discussed, as well as a comparison to thermal modulation results from the same system.</p><h3><strong>Video Transcription</strong></h3><p>Darshil Patel opened the presentation by discussing the concept of human odor and its transition after death. He explained that living humans possess a unique antemortem scent composed of volatile organic compounds (VOCs) released from the skin through microbiome activity, sweat, and breath. After death, this odor profile gradually changes into what is known as postmortem odor. The exact timing and progression of this transition remain poorly understood.</p><p>The presenter emphasized the practical importance of understanding this transition in disaster victim recovery operations. Search-and-rescue dogs are trained to detect odors associated with living individuals, whereas human remains detection dogs are trained to identify postmortem odors. Determining when antemortem odor disappears and postmortem odor becomes dominant can improve the deployment and training of these specialized canine units.</p><h4><strong>Research Objectives</strong></h4><p>The study focused on the early postmortem period in humans and aimed to:</p><ul><li>Characterize VOCs released during the fresh stage of decomposition</li><li>Track the evolution of donor VOC profiles over time</li><li>Identify the transition point between antemortem and postmortem odor</li></ul><p>Patel noted that prior to this research, only one study involving pig remains had examined odor transition during decomposition.</p><h4><strong>Human Decomposition Overview</strong></h4><p>The presenter reviewed the five major stages of decomposition:</p><ol><li>Fresh stage</li><li>Bloat stage</li><li>Active decay</li><li>Dry remains</li><li>Skeletonization</li></ol><p>The research concentrated specifically on the fresh stage, encompassing the earliest postmortem interval.</p><p>During this stage, several immediate physiological changes occur:</p><ul><li><strong>Algor mortis</strong> – cooling of the body</li><li><strong>Rigor mortis</strong> – stiffening of muscles</li><li><strong>Livor mortis</strong> – pooling of blood</li></ul><p>At the microscopic level, decomposition involves:</p><ul><li><strong>Autolysis</strong> – cellular breakdown</li><li><strong>Putrefaction</strong> – microbial degradation of tissues</li></ul><p>These processes generate VOCs that collectively contribute to postmortem odor.</p><h3><strong>Experimental Design</strong></h3><h4><strong>Human Donors and Study Sites</strong></h4><p>The study examined three human donors (cadavers) and monitored their VOC profiles both:</p><ul><li>In the morgue</li><li>At the REST outdoor decomposition research facility in Canada</li></ul><p>REST is currently the only Canadian outdoor human decomposition research facility.</p><h4><strong>VOC Sampling Procedures</strong></h4><h5>Morgue Sampling</h5><p>Upon arrival at the morgue:</p><ul><li>Bodies arrived enclosed in shroud-like materials or body bags</li><li>The bags were briefly opened to release VOCs accumulated during transportation</li><li>Bags were resealed for 20 minutes to allow VOC accumulation</li><li>VOCs were collected using:<ul><li>Tenax TA/Carbograph sorbent tubes</li><li>Active low-flow sampling pumps</li></ul></li><li>Sampling conditions:<ul><li>10-minute collection</li><li>100 mL/min flow rate</li></ul></li></ul><p>Background and body-bag controls were also collected.</p><h5>REST Facility Sampling</h5><p>At the outdoor decomposition facility:</p><ul><li>Donors were placed unclothed on their backs</li><li>Anti-scavenging cages protected remains from animals</li><li>During sampling:<ul><li>An aluminum hood was placed over the donor</li><li>VOCs accumulated for 20 minutes</li><li>VOCs were then collected onto sorbent tubes</li></ul></li></ul><p>Sampling conditions matched those used in the morgue to maintain methodological consistency.</p><h4><strong>Instrumentation and Analytical Workflow</strong></h4><h5><strong>GC×GC-TOFMS Analysis</strong></h5><p>Samples were analyzed using:</p><ul><li><a target="_blank" rel="noopener noreferrer" href="https://gcms.labrulez.com/products/37"><strong>LECO Pegasus BT system</strong></a></li><li>Mid-polar column combination with Stabilwax columns</li></ul><p>An internal standard was injected into every sample.</p><h5><strong>Decomposition Standard Mix</strong></h5><p>Researchers also analyzed a decomposition standard mixture containing 25 compounds previously reported in human decomposition studies. This standard was used to monitor method performance and VOC evolution throughout the study.</p><h4><strong>Data Processing Workflow</strong></h4><p>Initial data processing was conducted using <a target="_blank" rel="noopener noreferrer" href="https://gcms.labrulez.com/products/41"><strong>ChromaTOF software</strong></a> with the following criteria:</p><ul><li>Minimum signal-to-noise ratio: 100</li><li>Spectral similarity match: ≥850</li></ul><p>Further processing was completed in <strong>RStudio</strong>.</p><h5><strong>Data Filtering Steps</strong></h5><p>The workflow included:</p><ul><li>Exporting chromatographic peak tables as CSV files</li><li>Classification into experimental and control samples</li><li>Pairwise peak alignment</li><li>Normalization to internal standards</li><li>Removal of background contaminants</li><li>Filtering out siloxanes and column-derived artifacts</li><li>Manual verification using:<ul><li>ChromaTOF</li><li>NIST libraries</li></ul></li></ul><p>Final datasets contained normalized peak areas for validated compounds only.</p><h4><strong>Decomposition Observations</strong></h4><p>The three donors displayed visibly different decomposition trajectories despite being exposed to similar environmental conditions. Patel emphasized that decomposition is highly variable and no two bodies decompose identically.</p><h4><strong>Early Postmortem VOC Profiles</strong></h4><p>The early decomposition VOC profiles contained multiple chemical classes. The most abundant were:</p><ul><li>Nitrogen-containing compounds</li></ul><p>Acids were detected at relatively low abundance, which aligned with existing literature indicating acids typically become prominent during later decomposition stages.</p><h4><strong>Identification of VOC Categories</strong></h4><p>The researchers compared their VOC dataset with published literature describing:</p><ul><li>Antemortem VOCs from living humans</li><li>Postmortem VOCs from decomposition studies</li></ul><p>This comparison identified:</p><ul><li>24 VOCs associated with antemortem odor</li><li>35 VOCs associated with postmortem odor</li></ul><p>Additionally, a third category emerged:</p><ul><li>VOCs present in both antemortem and postmortem periods</li></ul><p>These compounds were termed:</p><h5><strong>“Transmortem VOCs”</strong></h5><p>In living humans, these VOCs were linked to skin emissions, while in decomposition they appeared associated with microbial breakdown processes.</p><h4><strong>Transition of Odor Profiles</strong></h4><p>The presenter analyzed VOC evolution over time using accumulated degree days (ADD), calculated from ambient temperature measurements.</p><p>Key observations included:</p><ul><li>Antemortem VOCs persisted throughout the early postmortem period</li><li>Transmortem VOCs were consistently detected</li><li>Postmortem VOCs increased sharply during later experimental days</li></ul><p>This pattern was observed consistently across all three donors.</p><h4><strong>Transition Point</strong></h4><p>Visual observations and chemical data both indicated that:</p><ul><li>Around experimental day 3</li><li>Bodies began transitioning toward the bloat stage</li><li>Postmortem VOC abundance increased substantially</li></ul><p>The study therefore proposed that the odor transition begins approximately around day 3 of decomposition under the tested outdoor conditions.</p><h4><strong>Implications for Detection Dogs</strong></h4><p>The persistence of antemortem and transmortem VOCs during early decomposition may explain why search-and-rescue dogs occasionally alert to deceased victims.</p><p>Patel suggested that overlapping odor signatures could create confusion for canine detection systems in disaster scenarios.</p><h4><strong>Conclusions</strong></h4><p>The study demonstrated that:</p><ul><li>The transition from antemortem to postmortem odor can be chemically monitored</li><li>Postmortem VOCs become dominant as decomposition progresses</li><li>Environmental decomposition studies provide valuable insight into odor evolution</li></ul><p>Patel emphasized that significantly more research is needed across:</p><ul><li>Different environments</li><li>Seasonal conditions</li><li>Additional donor populations</li></ul><p>to fully understand human odor transition after death.</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>

Identifying the transition from antemortem to post-mortem odor in cadavers cadavers in an outdoor environment (Darshil Patel, MDCW 2026)

<p><strong>Our Library never stops expanding. What are the most recent contributions to LabRulezGCMS Library in the week of 18th 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 / InfoMass</strong> and brochure by <strong>Thermo Fisher Scientific!</strong></p><h3><strong>1. MDCW / InfoMass: Development of a Fully Software-Controlled, Alignment-Free Loop-Delay Thermal Modulator for GC×GC</strong></h3><ul><li>Poster</li><li><a target="_blank" rel="noopener noreferrer" href="https://gcms.labrulez.com/labrulez-bucket-strapi-h3hsga3/P_22_Wu_0662310ba1.pdf"><strong>Full PDF for download</strong></a></li></ul><section><div><div><div><div><div><div><p>Loop-delay thermal modulation is a well-established approach for comprehensive two-dimensional gas chromatography (GC×GC) and inherently requires precise alignment of the modulation loop. In conventional designs, this alignment must be performed manually by the user, a process that is difficult, time-consuming, and often unreliable, as the modulation loop can shift during operation due to repeated hot-jet gas pulses, leading to misalignment and degraded modulation performance. This work addresses these limitations through a redesigned loop-delay modulator in which precise alignment is ensured intrinsically by the modulator geometry, eliminating user-dependent alignment while improving mechanical stability and operational robustness.&nbsp;</p><h4><strong>Key Improvements &nbsp;</strong></h4><ul><li>Intrinsic loop alignment by geometry, eliminating user-performed alignment&nbsp;</li><li>Mechanically secured loop holder, preventing loop movement during hot-jet gas pulses &nbsp;</li><li>Easy loop winding, simplifying installation and replacement&nbsp;</li><li>No moving mechanical parts, improving robustness and reliability&nbsp;</li><li>Fully software-controlled modulation, including hot-jet temperature, valve timing, modulation period, and cold-jet gas flow&nbsp;</li><li>Programmable cold-jet gas flow, providing indirect control of modulation temperature&nbsp;</li><li>Programmable modulation period, enabling flexible optimization for correcting peak wrap-around.&nbsp;</li><li>Independent of GC controls, enabling standalone operation</li></ul><h4><strong>Installation and Compatibility&nbsp;</strong></h4><p>Precise loop alignment is automatically achieved through the modulator’s mechanical design. The loop remains fixed during operation and is not affected by hot-jet gas pulses. The compact, modular system is compatible with most commercial gas chromatographs and operates independently of GC control hardware and software</p><h3><strong>2. Shimadzu: Simultaneous Analysis of Methoxypyrazines in Processed Tomato Products by GC–MS/MS with SPME Arrow</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_01141_en_78979e911f.pdf"><strong>Full PDF for download</strong></a></li></ul><h5><strong>User Benefits</strong></h5><ul><li>SPME Arrow enables high-sensitivity determination of methoxypyrazines in processed tomato products by efficiently preconcentrating volatile compounds.</li><li>GC–MS/MS in MRM mode provides isomer selectivity and reliable quantitation of methoxypyrazines, even in complex sample matrices.</li><li>The AOC-6000 Plus multifunctional autosampler automates SPME Arrow injection to increase throughput and improve repeatability.</li></ul><p>In processed vegetable foods and beverages, small changes in aroma and flavor can strongly affect perceived quality. For processed tomato products in particular, a vegetative (green) or hay-like off-flavor is often a key concern. This off-flavor has been linked to methoxypyrazines present at very low levels (ppt levels around 10 ng/L).&nbsp;</p><p>Methoxypyrazines include many closely related analogs. Therefore, a robust quantitative method must deliver both high sensitivity and sufficient selectivity (and/or separation) to handle real matrices.&nbsp;</p><p>In this article, five methoxypyrazines previously detected in vegetables (Table 1) were analyzed using a GC-MS/MS system with the <a target="_blank" rel="noopener noreferrer" href="https://gcms.labrulez.com/library?mainauthorItems=1&amp;search=SPME+Arrow"><strong>SPME Arrow</strong></a> injection method. The method provides stable quantitation at ng/L (ppt) levels, even in complex, interference-rich samples.</p><h4><strong>System Configuration</strong></h4><p>All measurements were performed with a <a target="_blank" rel="noopener noreferrer" href="https://gcms.labrulez.com/library?mainauthorItems=1&amp;search=GCMS-TQ8040+NX"><strong>GCMS-TQ8040 NX triple quadrupole</strong></a> GC–MS/MS system equipped with an <a target="_blank" rel="noopener noreferrer" href="https://gcms.labrulez.com/library?mainauthorItems=1&amp;search=AOC6000+Plus"><strong>AOC6000 Plus</strong></a> multifunctional autosampler (Fig. 1).&nbsp;</p><p>The AOC-6000 Plus supports multiple sample introduction techniques—including liquid injection, headspace, and SPME— and can switch between them automatically based on the method. This flexibility makes it well suited for laboratories that handle many sample types and applications.</p><h4><strong>Conclusion</strong></h4><p>By using an AOC-6000 Plus autosampler with the GCMS-TQ8040 NX system and optimizing the SPME Arrow injection method, five off-flavor methoxypyrazines were successfully measured at ng/L (ppt) levels. Using MRM improved selectivity and enabled isomer-specific analysis, including differentiation of isomers that are difficultto separate by GC alone.&nbsp;</p><p>When applied to real processed tomato products, the method enabled quantitation of 2-methoxy-3,5-dimethylpyrazine (MDMP). This system reduces matrix interference and provides high sensitivity for trace-level off-flavor compounds.</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.&nbsp;</p><h5><strong>Fugitive emissions of toxic VOCs&nbsp;</strong></h5><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><h5><strong>Analytical platform&nbsp;</strong></h5><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><h5><strong>Comprehensive data collection&nbsp;</strong></h5><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><h5><strong>Membrane inlet mass spectrometry&nbsp;</strong></h5><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 21, 2026

<p><strong>There are various ways to categorize gas chromatographic detectors. The main classifications include:</strong></p><ol><li>Detectors sensitive to concentration vs mass flow rate sensitive detectors</li><li>Selective vs universal (non-selective) detectors</li><li>Non-destructive vs destructive detectors</li></ol><p>A<strong> concentration-sensitive detector </strong>is one in which the <strong>peak response depends on the absolute analyte concentration</strong>. At constant concentration, the response is constant regardless of change in flow rate of the carrier gas. If the flow rate changed, there will be no effect on the peak height of the analytes.</p><p>On the other hand, a <strong>mass flow rate sensitive detector</strong> is one in which the<strong> peak response changes with the flow rate of the carrier gas</strong>. In other words, if the carrier gas flow rate is decreased, there will be a proportional decrease in peak height.</p><p><strong>Universal detectors </strong>can see a wider variety of compounds, whilst a<strong> selective detector </strong>is very specific to certain chemical elements or groups.<strong> Non-destructive detectors</strong> maintain the same structure of the analytes as they had whilst passing through the column, while<strong> destructive detectors </strong>break down the actual molecule to produce signals.</p><p>In GC analysis there is<strong> not much significance</strong> if the detector is<strong> destructive or non-destructive </strong>as there is no <strong>preparative work involved</strong>.</p><p><strong>Electron capture detectors</strong> (<strong>ECD</strong>) are <strong>mass flow dependent detectors selective to electronegative elements and they are also non-destructive.</strong> ECD is actually the go-to and most sensitive detector for the analysis of electronegative compounds.</p><p>The carrier gas is ionized by an electron source such as <strong><sup>3</sup>H </strong>or <strong><sup>63</sup>Ni</strong>. A low-energy stream of electrons produces a <strong>steady current </strong>that is magnified and measured. The<strong> current decreases </strong>when an electron-capturing compound enters the detector. Loss of electrons by the electronegative compound is measured as the signal.</p><p>ECD can detect from the picogram to <strong>nanogram level of concentration</strong>. As ECD is selective for electronegative compounds, it is the go-to detector for <strong>halogenated compounds, nitrogen-, oxygen-, and carbonyl group-containing compounds</strong>.</p><h4><strong>Points to Remember About ECD</strong></h4><ul><li>The ECD detector has a radioactive element in it. Maintenance of the detector should be performed only by qualified professionals with appropriate radioactive shielding. Hardware disposal is strictly regulated by local legislation.</li><li>The ECD is compatible with ultra-high-purity nitrogen and helium as the carrier gas.</li><li>Since the detector is a mass flow rate detector, there is a proportional impact on peak area and peak height with change in flow rate. The method should be run under constant flow mode for quantitative analysis.</li><li>Nitrogen or argon-methane mixture can be used as makeup gases. The makeup gas flow and composition should be optimized for higher sensitivity and maintained constantly between consecutive runs to obtain reproducible quantitative results.</li><li>The detector should operate at the temperature mentioned in the detector’s user manual. Usually, the upper limits are 350–400 °C, depending on the manufacturer and model. Most ECDs are equipped with automatic shut-down if the temperature limit is exceeded.</li><li>The carrier gas used for analysis should be free of oxygen, moisture, and halocarbons to extend detector lifetime and avoid baseline problems.</li></ul><p>ECDs can be baked out at higher temperatures to clean them. However, the<strong> bakeout temperature should not exceed the maximum limit </strong>mentioned in the detector’s user guide. Since ECD contains a radioactive beta particle source, no attempt should be made to<strong> clean the detector mechanically</strong>.</p>

What You Need to Know About Electron Capture Detectors

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News from LabRulezGCMS Library - Week 21, 2026

Identifying the transition from antemortem to post-mortem odor in cadavers cadavers in an outdoor environment (Darshil Patel, MDCW 2026)