News from LabRulezGCMS Library - Week 30, 2025

Our Library never stops expanding. What are the most recent contributions to LabRulezGCMS Library in the week of 21st July 2025? Check out new documents from the field of the gas phase, especially GC and GC/MS techniques!

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This week we bring you posters by Agilent Technologies / ASMS, Shimadzu / ASMS, presentation by UCT / MDCW and technical note by Thermo Fisher Scientific!

1. Agilent Technologies / ASMS: Beyond the Ion Source: Optimizing GC/MS Sensitivity with Capillary Chromatography  

• Poster
• Full PDF for download

Evolutions of ionization sources have allowed to push the limits of detection in gas chromatography/mass spectrometry (GC/MS) down to attogram levels with the Agilent 7010D triple quadrupole GC/MS system. At such low concentrations, impacts due to matrix, column phase selection, and thermal stability will have greater impact on peak shape and can have the potential to limit sensitivity. Additionally, interactions between solvent polarity and column phase polarity will also impact solvent focusing and may lead to the distortion of peaks. In the analysis of trace-level analytes, splitless and pulse splitless injections are needed to achieve the desired sensitivity, but this will also increase the solvent introduced to the head of the gas chromatography column and the possibility of interactions between the solvent and the analytical column phase.¹ 

In this poster we will examine how interactions between traditional and nontraditional solvents and column phase used in gas chromatography impact sensitivity, illustrate the mechanism of action, and discuss strategies to mitigate risk and maintain sensitivity for trace level analytes.

Experimental

An Agilent 8890 GC coupled with an Agilent 7010D HES 2.0 was used for data acquisition and Agilent MassHunter Qualitative Analysis software, version 10.0, was used for data analysis. A representative pesticide mixture, Agilent Pesticide checkout solution (p/n 5190-0468), was prepared in acetonitrile and dichloromethane at concentrations ranging from 10 to 500 ppb to monitor analyte response from interactions between column phase and solvent polarity.

The Role of Thermal Stability and Solvent Focusing

A factor for determining the thermal stability of a GC column is due in part to the deactivation process of the fused silica and the natural presence of silanols on the surface of the fused silica. Depending on how the fused silica is produced, there can be differences in the concentration of silanols present, fully hydrated silica, and can range from 6 to 10 silanols per square nanometer on the capillary surface. 

As analytes and solvent diffuse into and out of the analytical column phase, they will also interact with free silanols, and can lead to activity, which is why it is important to perform a silanol deactivation. This deactivation will decrease the silanol content as much as possible and can be done in a variety of ways.⁷ 

Polar solvents will have a greater affinity for silanols, and when the solvent is recondensed at the head of the column, the interaction between the solvent and silanols can cause a decreased flooded zone. Conversely, when less free silanols are present, the solvent has less affinity for the column phase and will cause an increase in the flooded zone.

With recent advancements in deactivation technologies, it has been possible to create a deactivation that further decreases the silanol content on the fused silica surface, creating ultrathermally stable and ultra inert columns. But as their silanol content is further decreased, mismatch in solvent polarity and column phase can lead to an increase of the flooded zone, especially in the case of splitless injections where the initial starting oven temperature is lower than the boiling point of the solvent.

Conclusion

For a gas chromatography analysis to be successful there are many factors to consider, such as injection speed, solvent choice, installation of the column, and column phase selection. Solvent selection is important in more decisions than determining which solvent will dissolve analytes. Splitless injections will be more impacted by solvent selection, as there will be a greater amount of solvent introduced to the column and greater interactions between the solvent and column phase. To mitigate the problem of using a polar solvent with a nonpolar column, a guard column can be used to help refocus the solvent and analytes at the head of the analytical column and improve analyte peak shape.

2. UCT Prague / MDCW: Forensic olfactronics and human scent signatures created from GC×GC-MS data 

• Presentation
• Full PDF for download

The concept of forensic olfactronics explores the complex and unique chemical profile of human scent as a tool for personal identification. Originally motivated by a request from the Czech police, Prof. Štěpán Urban and his team at UCT Prague began analyzing human scent samples to support canine-based identification. Despite the limited scientific literature available, the team discovered that human scent is an intricate mixture of over 100,000 compounds with vastly differing concentrations.

Using comprehensive two-dimensional gas chromatography coupled with time-of-flight mass spectrometry (GC×GC-TOF-MS), the researchers achieved unprecedented resolution of scent profiles. They categorized scent compounds into primary (genetically determined), secondary (lifestyle- and environment-dependent), and tertiary (external influences). Focusing on primary scent markers, they developed digital scent signatures that enable individual identification based on the unique concentration ratios of these compounds.

Beyond forensics, the method also allows classification based on gender, ethnicity, blood type, and even the use of hormonal contraception. Emerging applications in medical olfactronics are especially promising, as changes in primary scent composition may signal genetic mutations or degenerative diseases like diabetes, Alzheimer’s, and cancer. These findings suggest a new frontier where scent analysis contributes not only to justice, but also to personalized diagnostics.

As part of ongoing development, Urban’s team continues to build a scent signature database and refine analytical techniques. Their research positions GC×GC-MS not just as a forensic tool, but as a powerful platform for studying the human body through the chemistry of scent.

3. Shimadzu / ASMS: Ensuring drinking water quality through a single method of VOCs analysis and taste- and odor-causing substances

• Poster
• Full PDF for download

Monitoring contaminants in drinking water is essential to protect public health. A recurring issue is the presence of off-flavor (musty and earthy odor), mainly caused by the compounds 2- methylisoborneol (2-MIB) and geosmin, produced by cyanobacteria and actinobacteria. Brazilian regulations, such as CONAMA Resolution No. 357 and Portaria GM/MS 888/21, define limits for volatile organic compounds (VOCs), but lack of limits for musty/earthy odor substances. Regarding to the method, the US EPA 524.4, from the United States Environmental Protection Agency (USEPA), proposes the analysis of VOCs by GC-MS coupled to Purge & Trap as sample introduction technique

Considering the need for versatility, a unique method was developed that allows the simultaneous analysis of VOCs, 2-MIB, and geosmin in a single run.

Methods

• The P&T system was used, which is a dynamic headspace system, in which purge gas is passed through the water sample, and the volatile analytes are forcibly expelled with the purge gas and trapped by an appropriate adsorbent (Fig 1).
• The EST Analytical Evolution2 Purge & Trap concentrator and Centurion autosampler were interfaced to a Shimadzu GCMSTQ8050 NX (Fig 2)
• In accordance with the method EPA 524.4, the analysis was configured in Selected Ion Monitoring (SIM) mode. The compound 1-Bromo-4-Fluorobenzene (BFB) was used as the internal standard and nitrogen was used as the purge gas, due to the shortage and high cost of high purity helium.
• Therefore, helium was exclusively used as the carrier gas. Ultrapure water samples were fortified with target compounds, covering a concentration range of 0.1 to 10 ppb, for 20 different compounds and a range of 5.0 to 50 ppb for the 1,4-Dioxane compound.
• To achieve high analytical sensitivity and a low LOQ for the odor-causing compounds, it was necessary to acquire in Multiple Reaction Monitoring (MRM) mode, the method operated in simultaneous SIM/MRM mode.

Results and Discussion

Using the P&T-GC-MS/MS system for single method analysis, the chromatographic runtime was 18 minutes. The substances were separated using a 0.25 mm × 30 m × 1.4 ȝP SH-I-624Sil MS capillary column. The chromatogram from a single injection of VOCs, 2-MIB, and geosmin is represented in Fig 3.

Conclusion

The results obtained demonstrated the feasibility of using these instruments to monitoring drinking water quality through the most comprehensive methodology possible, in compliance with Brazilian regulations and EPA Method 524.4. This study stands out due to the lack of single, highly sensitive methods for comprehensive drinking water analysis that include all purgeable VOCs, especially when using nitrogen as the purge gas and taste and odor (T&O) compounds, as required by Brazilian standards. Specifically for 2-MIB and geosmin, the most commonly used analytical technique is solid-phase microextraction (SPME). However, integrating the analysis of all these compounds into a single analytical method is essential in terms of productivity, operational simplicity, and analytical sensitivity.

4. Thermo Fisher Scientific: Grant application resource: Using the Orbitrap Exploris GC 240 mass spectrometer to accelerate research 

• Technical note
• Full PDF for download

Scientific research laboratories need to obtain confident results while maintaining the highest levels of accuracy and confidence. For many researchers, it is critical to have the flexibility and analytical power to tackle a diverse range of analytical challenges to gain a comprehensive understanding of their samples. Most of these laboratories rely on both targeted and untargeted analytical approaches, using both gas chromatography and liquid chromatography coupled to single quadrupole or triple quadrupole mass spectrometry (MS) instrumentation. These systems cover the wide range of chemical classes to be detected but provide only limited information for discovery workflows. For targeted applications, they are limited to detect only those compounds in the target list, and they require careful optimization of acquisition parameters for each compound. High-resolution, full scan mass spectrometry using Orbitrap technology provides a solution to: 

• Detection and quantification of an increasing number of compounds 
• Identification and elucidation of the chemical composition and structure of unknown compounds 
• Retrospective analysis of samples long after data acquisition 

High-resolution Orbitrap mass spectrometry has been available with both liquid and gas chromatography for many years and has proven to be a highly valuable analytical technique. More recently, the technology in gas chromatography moved to join the Thermo Scientific Orbitrap Exploris Mass Spectrometer series. This new platform of a benchtop hybrid quadrupole-Orbitrap mass spectrometer opens up new research opportunities in a system with significantly reduced footprint, saving both energy and raw materials in their manufacture. 

High-resolution Orbitrap mass spectrometry has proven to be a highly valuable analytical technique for both analytical science and scientific research applications. 1-3 Orbitrap mass spectrometry technology coupled to gas chromatography (GC) has evolved with the Orbitrap Exploris GC 240 mass spectrometer system (Figure 1), which delivers a maximum resolving power of 240,000 (FWHM at m/z 200), in a compact design and with intelligent informatic solutions. Researchers gain the ability to have the right answers the first time and the flexibility to adapt to ever changing needs from superior mass accuracy, dynamic range, and robustness.

Additional features for research applications: 

• Thermo Scientific™ ExtractaBrite™ Electron Ionization (EI) source
•  Ion source includes ion volume, repeller, source lenses, RF lens, and dual filaments in all ionization modes, programmable from 50 ˚C to 350 ˚C
•  VeV tuning allows optimized low electron energy acquisition down to 8 eV 
• Chemical ionization (CI) source for acquisition with positive ion chemical ionization (PCI) and negative ion chemical ionization (NCI) 
• Entire ion source can be removed or changed to a CI source in under 2 minutes without venting 
• Vent-free column exchange with patented source plug combination EI/PCI/NCI ion volume can be used without the need for source interchange

Conclusions 

• With unprecedented resolving power of 240,000 and consistent sub-ppm mass accuracy, the Orbitrap Exploris GC 240 mass spectrometer is a unique laboratory tool for targeted and discovery workflows, where screening, quantitation, compound identification, and structural elucidation applications are required. 
• The Orbitrap Exploris GC 240 mass spectrometer provides selectivity to resolve target compounds from other interfering compounds and/or from matrix ions of similar mass, which is essential for the compound confirmation in targeted or untargeted experiments. As an example, a mass resolving power of 240,000 (corresponding to a mass resolution of 230,000 at m/z 167.08113) is needed to separate bifenthrin from the background interfering ions in a soil sample extract. 
• High sensitivity is maintained across all resolving power settings, ensuring unmatched analytical performance irrespective of matrix complexity and providing limits of detection of ppt levels. 
• Excellent sub-ppm mass accuracy accelerates the identification of elemental composition and compound identification in unknown workflows by allowing the use of narrow mass tolerances. 
• Availability of soft chemical ionization, such as PCI coupled with MS/MS, allows for structural elucidation and confirmation of parent molecules using accurate mass information.