Thermal treatment hyphenated with gas chromatography is a versatile and powerful tool in the study of polymer characterization. An inexpensive system where thermal treatment at different temperatures occurs inside a PTV injector is described. The samples investigated, commercial plastics, are complex mixtures that contain several polymers and additives. These plastics as well as their pure constituents are subjected to multi-step thermal treatment. The individual chromatograms of the various constituents of polymeric sample are correlated with those of the final material in order to indentify additives (thermal desorbtion) and degradation products (pyrolysis). Results obtained with the new method indicate the interesting potentials of the technique for the characterization of polymer compositions. Reproducibility of absolute and relative peak areas has been considered and found to be acceptable. The absence of a heated transfer line and switching valves, which are always present in conventional sep-ups, eliminates the risk of losses of high molecular weight components. Further advantages of the technique proposed are simplicity, versatility and its inexpensive nature.

Thermally assisted hydrolysis and methylation-gas chromatography (THM-GC) is an important tool to analyse fatty acid in complex matrices. Since THM-GC has major drawbacks such as isomerisation when applied to fatty acids in natural matrices, a direct thermal desorption (DTD) interface and an incubation time of 30 min were used to circumvent these problems. Using vegetable oils such as sunflower oil and triarachidonin, the conversion of triglycerides into their fatty acid methyl esters (FAMEs) was investigated. The yields using a DTD (and trimethylsulfonium hydroxide as a reagent) were found to be similar or even higher than when applying a conventional off-line method, while the FAME profiles were identical. When the procedure was applied to analyse the FAME profiles of microbial cells in a methanolic or aqueous suspension, it was found that accurate profiles are obtained for such samples. Thus, the present approach opens the route to analyse fatty acids in microbial cells in a fully automated fashion, which will allow high sample throughput.

A direct thermal desorption (DTD) interface was applied to profile the fatty acid composition of whole/intact aquatic micro-organisms using trimethylsulfonium hydroxide (TMSH) as derivatization reagent in a fully automated fashion without any sample treatment. DTD was used to release cellular free and esterified fatty acids, after conversion into their methyl esters, from the very limited amounts of cells available in plankton community analysis using fluorescence-activated cell sorting of mixed (natural) microbial/algal populations. The liner of the GC injector is used as a sample-and-reaction container with the aid of the DTD interface. The fatty acids are converted into their methyl esters after an incubation (hydrolysis) time of 30min with TMSH. After transportation into the injector, the liner is heated to effect thermally assisted methylation. Simultaneously, the fatty acid methyl esters (FAMEs) are introduced from the liner into the capillary GC column.On the basis of peak intensities, the fatty acid compositions, thus obtained, were shown to be closely similar to those of a conventional lipid extraction and methylation procedure.The method was applied to some common freshwater algae, the green algae Scenedesmus acutus, the diatom Asterionella formosa and the filamentous cyanobacterium, Limnothrix sp. strain MRI. Using this novel method, poly-unsaturated fatty acids were methylated into their corresponding methyl esters without isomerization/pyrolytic side-reactions.The present method has been used to perform large series of analyses of algal and microbial cells. Up to 18 samples could be analysed per day. In order to reach this sample throughput, preparation of the ( n+1)th sample was performed simultaneously with GC analysis of the nth sample.

On-line coupled size exclusion chromatography–pyrolysis gas chromatography mass spectrometry (SEC–Py-GC–MS) is studied as a novel tool for the characterization of complex polymer samples. An automated system for on-line SEC–Py-GC–MS allowing transfer of multiple fractions was developed based on stop-flow operation of the SEC dimension, syringe-based transfer of the SEC fraction to the GC instrument and solvent elimination with subsequent pyrolysis in a programmed temperature vaporization (PTV) injector. After optimization the system was applied to the characterization of a complex terpolymer composed of very similar monomers. The use of the system for combined pyrolysis and additive analyses in polycarbonate was also demonstrated. Results obtained with the new method indicate the interesting potentials of the method for detailed characterization of polymeric materials.

Size-exclusion chromatography (SEC) and pyrolysis-gas chromatography (Py-GC) are commonly used to characterize copolymers. SEC is a powerful method to determine the molecular-weight distribution of polymers whereas Py-GC provides valuable information on their chemical composition. The combination of these two techniques could yield combined size and composition information for copolymers or polymer mixtures. A fully automated system was constructed to perform these two-dimensional (2D) characterizations...

The feasibility of a versatile system for multi-step direct thermal desorption (DTD) coupled to comprehensive gas chromatography (GCxGC) with time-of-flight mass spectrometric (TOF-MS) detection is studied. As an application the system is used for the characterization of fresh versus aged olive oil after treatment at 70, 175, 250 and 600°C.

In this paper, we discuss the use of a direct thermal desorption (DTD) interface as an alternative to Curie-point flash pyrolysis system as an inlet technique in gas chromatography-combustion isotope-ratio mass spectrometry (GC/C-IRMS) analysis of whole/intact phytoplankton and zooplankton specimens. The DTD in combination with a combipal auto-injector is programmed to perform the injection, evaporation of solvents, transport of capped programmed-temperature vaporizer (PTV) liners to the PTV injector and chemical derivatisation (thermally assisted hydrolysis/methylation; THM) such that a profile of a cellular fatty acids is obtained. Flow-cytometric sorted microalgae and handpicked zooplankton are used as samples with trimethylsulfonium hydroxide (TMSH) as methylating reagent. A major advantage of this novel approach over the Curie-point technique is the automation of the total procedure, which allows unattended analysis of large sample series. The profiles and delta(13)C carbon isotopic signatures of the fatty acid methyl esters (FAMEs) produced are very similar to those obtained using the Curie-point flash pyrolysis method. It is shown that algal samples must be kept no longer than 48h in the DTD sample tray prior to the THM-analysis in order to maintain the integrity of their FAME profile.

Gas chromatography (GC) has in recent times become an important tool for the fatty acid profiling of human blood and plasma. An at-line procedure used in the fatty acid profiling of whole/intact aquatic micro-organisms without any sample preparation was adapted for this work. A direct thermal desorption (DTD) interface was used to profile the fatty acid composition of human plasma and whole human blood of eight volunteers in a procedure omitting the usual lipid extraction steps that precede sample methylation in the traditional (off-line) protocols. Trimethylsulfonium hydroxide (TMSH) was used as reagent for thermally assisted methylation. In a fully automated manner, the liner of the GC injector is used as a sample-and-reaction container with the aid of the DTD interface. The fatty acid methyl ester (FAME) profiles obtained using this novel approach, were very identical to those obtained when the traditional off-line protocol was applied. FAME yields obtained in the at-line DTD method were found to be very similar for saturated fatty acids, but significantly higher for polyunsaturated fatty acids compared to off-line yields. As a result of the contribution of circulating cell membranes in blood, substantial differences were observed when the amount of FAMEs obtained in whole human blood and human plasma samples were compared after their analysis. Thanks to the fully automated operation of this novel procedure, large series of analyses can easily be performed.

Gas chromatography is an important analytical technique for qualitative and quantitative analysis in a wide range of application areas. It is fast, provides a high peak capacity, is sensitive and allows combination with a wide range of selective detection methods including mass spectrometry. However, the application area of GC is limited because the molecules to be analysed have to be thermally stable and sufficiently volatile. Numerous molecules do not meet these requirements and hence are not amenable to direct GC analysis. Recent research has resulted in better chromatographic columns and methods for sample preparation that enable a significant expansion of the molecular application range of GC. The strategies exploited include conversion of (macro)molecules into smaller species and approaches to reduce the polarity of molecules. In this review we identify four generic routes for extending the applicability of GC. These include high-temperature GC, derivatisation, pyrolysis and thermochemolysis. The principles, recent developments and future perspectives of these routes are discussed and examples of applications using the different options will be shown. Life sciences, metabonomics and profiling strategies for sample characterization are identified as important future drivers for the continued development of GC.

A recently developed hyphenated system for “organic” size-exclusion chromatography–pyrolysis-gas chromatography–mass spectrometry (SEC–Py-GC–MS) is adapted to allow the use of aqueous LC eluents as applied in the characterization of water-soluble polymers. The system uses syringe-based transfer of multiple LC-fractions to the GC instrument with solvent elimination and subsequent pyrolysis in a programmed temperature vaporization injector. The problems of the large-volume injections of aqueous, salt containing eluents into the Pyrolysis GC–MS are solved by using a ‘sintered-bed liner’ for elimination of the water at a high temperature, a volatile salt and the installation of a back-flush option. After optimization, the system was applied for the determination of the combined molecular weight–chemical composition of a polyethylene glycol–polypropylene glycol block copolymer. This analysis was done with the system in the aqueous SEC–Py-GC–MS mode. Also demonstrated is the automated at-line characterization of a random polystyrene–polymethylmethacrylate copolymer, now with the system in the gradient reversed-phase LC–Py-GC–MS mode. The methods proposed in the present work are very useful for the detailed characterization of water-soluble copolymers.

Unlike single compounds, polymers consist of many different molecules. These molecules are derived from the same building blocks, but diier in chain length, end-group, degree of branching, etc. For a true understanding of a polymer and its properties detailed knowledge of all features is necessary. Here it is generally not sufficient to just know the average distribution of isolated single parameters such as the molecular weight distribution or the average composition of the polymer. Multi-dimensional information is needed, giving for example copolymer composition as a function of molecular weight. Hyphenated combinations of a liquid chromatographic separation and pyrolysis GC provide an ideal means of deriving such information, as will be shown below.