News from LabRulezGCMS Library - Week 36, 2026

The presentation “The Century Mix: updates and cool projects” introduces the Century Mix, a standardized reference mixture developed for comprehensive two-dimensional gas chromatography (GC×GC). The mixture contains 100 compounds representing a broad range of chemical classes, including alkanes, alcohols, ketones, esters, lactones, phthalates, and aromatic compounds. Stability was a key criterion in compound selection, and the mixture was developed through cross-laboratory collaboration for column characterization, method assessment, and quality control. Its structured chromatographic behavior also makes it useful for studying how different compound classes behave in GC×GC separations.

A major part of the work examined the factors influencing retention indices (RI) in GC×GC systems, which are important for reliable compound annotation in non-targeted analysis. An inter-laboratory study involved 11 GC×GC systems using cryogenic, Peltier, and flow modulation, different detectors, and both normal and reversed column configurations. Principal component analysis showed clear grouping according to normal versus reversed orthogonality, confirming the strong influence of stationary-phase configuration. A subsequent design-of-experiments study evaluated 140 combinations of temperature ramp rate, carrier-gas flow rate, modulation period, and secondary-oven temperature offset.

The results showed that the influence of experimental conditions is strongly compound dependent. Of the compounds evaluated in the statistical model, 33 showed RI variation that could be linked to the investigated parameters, whereas 43 did not follow the model well. Compounds such as quinoline, phthalates, lactones, terpenes, and some aromatic compounds showed particularly pronounced effects. For quinoline, for example, the model explained about 93% of RI variability, with differences of approximately 75 RI units across the tested conditions, while 2-hexanone showed considerably weaker dependence. Overall, temperature ramp rate and flow rate emerged as particularly important parameters, although the magnitude of their effect depended on compound chemistry and column configuration.

The Century Mix is therefore being developed not only as a characterization mixture but also as a tool for system quality control and more reliable retention-index prediction. Repeated standardized QC measurements demonstrated very low RI variability and can be used to monitor system stability, experimental effects, and potential instrument drift. The broader goal is to better understand the fundamental chemistry governing GC×GC retention and ultimately improve method development, data processing, and identification of unknown compounds by combining high-quality separations, mass spectra, and predicted retention information.

3. Shimadzu: Determination of Free and Total Glycerol and Mono-, Di-, and Triglyceride Contents in Biodiesel According to EN 14105

• Application note
• Full PDF for download

User benefits

• Nexis GC-2060 offers reliable analysis of biodiesel samples regarding their free and total glycerol and mono-, di-, and triglyceride contents, using hydrogen as a cost-effective carrier gas 
• Hydrogen carrier gas can be used safely through built-in safety measures
• The multi-mode injection unit (MMI) allows selection of the preferred injection mode – direct (simple OCI) or convenient splitless PTV mode – both delivering excellent instrument performance in line with the standard’s requirements

Playing a vital part in countries’ efforts to lower greenhouse gas emissions, biofuels can be manufactured from various feedstocks such as vegetable oils, animal-derived fats, and recycled cooking oils. Biodiesel production predominantly uses rapeseed, soybean, and palm oils. Because feedstocks are so varied, ongoing quality monitoring is essential - since the raw material’s quality greatly influencesthe final biodiesel quality. 

The EN 14105:2024 describes the determination of free and total glycerol contents and mono-, di-, and triglyceride contents in biodiesel by means of gas chromatography with flame ionization detection (GC-FID). Injection shall be performed via on-column injector or an equivalent device¹. 

This study shows the analysis of biodiesel originating from rapeseed, soybean, and palm oil using the Nexis GC-2060 gas chromatograph and its multi-mode injection unit (MMI).

Configuration and Analysis Conditions

Gas chromatograph Nexis GC-2060 with multi-mode injection unit (MMI), flame-ionization detector (FID) and autosampler AOC -30i.

Conclusion 

Nexis and AOC are trademarks of Shimadzu Corporation or its affiliated companies in Japan and/or other countries.. Nexis GC-2060 provides reliable analysis of biodiesel samples for glycerol and glyceride contents according to EN 14105:2024 across the commonly used feedstocks. It supports hydrogen as a cost-effective carrier gas, while the multi-mode injection unit (MMI) offers selection of the injection mode based on user preference: direct mode representing simple on-column (OCI) analysis or splitless programmed temperature vaporization (PTV) mode as a convenient alternative that delivers comparable performance.

4. Thermo Fisher Scientific: Streamlined static headspace GC–MS approach for detection of impurities in recycled PET

• Application note
• Full PDF for download

Polyethylene terephthalate (PET) is a widely used thermoplastic polymer valued for its strength, low weight, durability, and adaptability. Owing to these properties, it is extensively applied in packaging, textile fibers, and electronic components. PET is particularly suitable for recycling because it can be melted and reshaped multiple times with minimal loss of performance, and it is easily recognizable by the recycling code “1” (♳). The recycling of PET involves several stages, including collection, sorting, transport, processing, washing, pelletizing, and remanufacturing into new products [1]. However, during these steps, contaminants such as plasticizers, residual monomers, and degradation byproducts may be introduced. 

The presence of such substances can pose potential risks to both environmental and human health, making the identification and characterization of contaminants in recycled PET essential for evaluating material quality and safety. Among the non-intentionally added substances (NIAS), benzene, acetaldehyde, and limonene are of particular relevance. Benzene is a recognized carcinogen and represents a serious health concern if present in PET. It may form as a degradation product of PET, with the reaction catalyzed by acidic compounds released at high temperatures by polymer impurities such as polyvinyl chloride (PVC). Poor temperature control or overheating can increase benzene formation as a degradation byproduct. Acetaldehyde, another degradation product of PET generated during bottle manufacturing, can alter the sensory properties of bottled beverages. Limonene, a flavor compound commonly present in soft drinks, may be absorbed into recycled PET and subsequently migrate into packaged beverages, potentially affecting product quality. 

Gas chromatography coupled to headspace sampling is a fast and simple technique that enables the extraction of volatile and semivolatile compounds from solid and liquid samples without the need for time-consuming sample preparation. 

In this study, headspace sampling coupled to single quadrupole mass spectrometry was used to assess the overall quantitative performance for analysis of acetaldehyde, benzene, and limonene in recycled PET packaging. 

The capability of the Thermo Scientific™ ISQ™ 7610 single quadrupole GC–MS of combining the simultaneous acquisition of both single ion monitoring (SIM) and full scan (FS) allowed for sensitive targeted analysis as well as screening of unknown contaminants possibly present in recycled PET bottles.

Experimental 

In all experiments, a TriPlus 500 HS autosampler was coupled to a Thermo Scientific™ TRACE™ 1610 Gas Chromatograph (GC), configured with a Thermo Scientific™ iConnect™ Split/splitless Injector Module (iConnect-SSL), and connected to an ISQ 7610 single quadrupole mass spectrometer. 

The separation of the target analytes was achieved using a Thermo Scientific™ Trace GOLD™ TG-624 SILMS capillary column, 60 m x 0.25 mm x 1.4 µm (Part No. 26059-3330). This column provides a low to mid polarity phase with high thermal stability (maximum operating temperatures up to 320 °C) and high inertness, enabling Gaussian peak shapes for analysis of volatile organics. The TriPlus 500 HS autosampler is connected directly to the analytical column, removing the use of a long external transfer line. In this configuration, the SSL injector module is used only for the pneumatic control of the carrier gas and split flow.

Conclusions 

The results presented in this work demonstrate that headspace coupled to GC–MS provides a suitable and simple solution for analysis of contaminants in rPET, with no complex sample preparation required. 

• The capability of combining FS with SIM acquisition allows for qualitative and quantitative analysis, increasing confidence in compound identification through spectral comparison with NIST library and allowing for the detection of possible analyte co-elution. 
• The TriPlus 500 HS autosampler provides highly repeatable solventless extraction from solid samples with absolute area counts RSD < 5%, permitting reliable and consistent quantitative data. 
• The ISQ 7610 single quadrupole GC–MS demonstrates an extended linear response (≥ 4–5 orders of magnitude) with R2 ≥ 0.997, calculated amounts within ± 20% the expected value, and ion ratio deviation ≤ 15% across the calibration curve. 
• Sensitivity was demonstrated with overall calculated LOD ≤ 0.03 ng/µL.
• Chromeleon CDS helps ensure data integrity, traceability, and effective data management from instrument control to the final report streamlining analysis and data review processes.