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Thermally assisted hydrolysis and methylation-gas chromatography (THM-GC) using a vertical microfurnace pyrolyzer and a flame ionization detector (FID) was applied to rapid analysis of chemical composition for polyunsaturated fatty acid (PUFA) components in human serum. Here, the authors used a reactive thermal desorption (RTD) method, where 2 μL of a serum sample was subjected to the THM reaction at 250 °C for 20 s, to detect PUFA components with high selectivity and sensitivity. The resulting chromatograms clearly showed a series of fatty acid methyl esters including PUFAs without any interference peaks derived from the matrix components of the serum samples. Furthermore, the observed chemical composition and n-6 / n-3 ratio for PUFA components were in good agreement with those obtained by a conventional analytical technique involving solvent extraction and transmethylation. • Reactive thermal desorption (RTD) enabled selective detection of PUFAs. • N-6 / n-3 PUFA ratios were analyzed rapidly and conveniently. • Only 2 μL of a human serum sample was enough to be analyzed. • Tedious and time-consuming sample pretreatments were not required. [ABSTRACT FROM AUTHOR]

The presence of phenolic compounds, possessing outstanding antioxidant activity corresponding to ascorbic acid, in wasted acorn shells was revealed by means of thermochemolysis-gas chromatography/mass spectrometry (thermochemolysis-GC/MS) in the presence of organic alkalis. The chromatogram of intact acorn shell samples obtained by thermochemolysis-GC/MS using tetramethylammonium hydroxide (TMAH) showed a strong peak of 3,4,5-trimethoxybenzoic acid methyl ester. This product was also clearly observed on the chromatograms of the methanol and water extracts from the acorn shells, indicating that 3,4,5-trimethoxybenzoic acid methyl ester was derived from free and/or esterified gallic acids through the thermochemolysis reaction. Based on the peak intensities, the contents of gallic acid components were determined as ca. 27 wt% for the both extracts. Furthermore, the content of free gallic acid was selectively estimated with discriminating from its esterified counterpart by using tetramethylammonium acetate (TMAAc) as a methylating reagent. These results were also correlated with high antioxidant activity of the acorn shell extracts evaluated by a DPPH radical scavenging method. [ABSTRACT FROM AUTHOR]

Abstract: Thermochemolysis-gas chromatography in the presence of tetrabutylammonium hydroxide was applied to the direct determination of phenolic compounds present as “extractives” in a wood sample (Eucalyptus camaldulensis). The phenolic extractives converted into their perbutyl derivatives were separated from the other phenolic products derived from the lignin skeleton in the observed chromatogram of the wood sample. On the basis of their peak intensities, the contents of the phenolic extractives in the wood sample were rapidly and precisely determined without using preliminary solvent extraction of the wood sample. [Copyright &y& Elsevier]

Abstract: The molecular structure of lipids in whole bacteria cells was characterized in detail by using two different and complementarily direct analyses; thermally assisted hydrolysis and methylation-gas chromatography (THM-GC) and matrix-assisted laser desorption/ionization mass spectrometry (MALDI-MS) combined with on-probe sample pretreatment. First, THM-GC in the presence of tetramethylammonium hydroxide (TMAH) was applied to compositional analysis of the fatty acid components of lipids in whole bacterial cells. On the resulting chromatograms, a series of fatty acid components in bacterial lipids were clearly observed as resolved peaks of their methyl esters. The fatty acid compositions determined on the basis of the peak intensities were in good agreement with those obtained by the conventional technique involving solvent extraction of the lipids in the samples. Furthermore, MALDI-MS combined with the on-probe sample treatment, using 2,5-dihydroxybenzoic acid (DHB) and sodium iodide (NaI) as matrix and cationization reagents, respectively, was used to detect intact phospholipids directly from whole bacterial cells. The MALDI spectra thus obtained showed an array of ions generated from bacterial phospholipids, such as phosphatidylethanolamines (PEs) and phosphatidylglycerols (PGs). Finally, the bacterial lipids were comprehensively characterized in terms of the acyl groups and the molecular structures by taking both of the results obtained by THM-GC and MALDI-MS into consideration. [Copyright &y& Elsevier]

Abstract: The effect of off-line alkylation using a powerful methylating reagent of carbanion and methyl iodide on the kind and yield of degradation products of humic and fulvic acids in their pyrolysis-gas chromatography (Py-GC) was examined. The humic and fulvic acids used were prepared from three soils including a Dystric Cambisol, an Umbric Andosol, and a Podzol. The yields of aliphatic and lignin-derived phenolic compounds did not increase or decreased generally after the off-line methylation in comparison with conventional thermally assisted hydrolysis and methylation (THM) using tetramethylammonium hydroxide (TMAH) for unmethylated samples. However, benzenetetracarboxylic acid tetramethyl esters and benzenepentacarboxylic acid pentamethyl ester became detectable or increased in yield for all the three fulvic acids examined and one humic acid sample characterized by its high concentration of carboxyl groups. Benzenehexacarboxylic acid hexamethyl ester was also detected in off-line methylated fulvic acids soluble in dichloromethane and purified with Sephadex LH-20. The addition of TMAH in pyrolysis of the off-line methylated samples did not improve the yields. Hence, the conventional THM comparatively lead to lower yields of the benzenepolycarboxylic acids (BPCAs) with 4–6 carboxyl groups, and the Py-GC after the off-line methylation could give additional information on structural unit of humic substances, although its single use did not increase total yields of degradation products. [Copyright &y& Elsevier]

Thermally assisted hydrolysis and methylation-gas chromatography (THM-GC) in the presence of trimethylsulfonium hydroxide (TMSH) was applied to the analysis of the lipid contents and their fatty acid compositions in individual zooplankters, especially focusing on polyunsaturated fatty acid (PUFA) components. On the resulting chromatograms, fatty acid components including PUFAs such as eicosapentaenoic acid (EPA; C20:5) and docosahexaenoic acid (DHA; C22:6) in single zooplankters were clearly observed as their methyl esters without doing any tedious and time-consuming pretreatment. By using this technique, the lipid contents and fatty acid compositions in a powdered plankter sample prepared by cryomilling homogenization were estimated on the basis of the observed peak intensities with relative standard deviations of less than 6%. The fatty acid compositions thus determined were in good agreement with those obtained by the conventional technique involving solvent extraction of the samples for every fatty acid component including PUFAs. The differences among individual zooplankter samples were then evaluated by THM-GC method. As a result, the chemical compositions of EPA and DHA showed relatively large inter-individual fluctuations even for the samples cultured under the same conditions. This suggests that lipid biosynthesis of the highly unsaturated fatty acid components and their consumption proceeded differently depending on the life history for each individual zooplankter. [Copyright &y& Elsevier]

Highlights • THM-GC was applied to monitor the change in copolymer composition of film samples during soil burial test. • 3 HHx moieties in the polymer chains were preferentially biodegraded owing to their low crystallinity. • Local variation in the degree of biodegradation using only 30 μg of P(3HB-co-3HHx) film sample. Abstract Soil burial biodegradation behavior of poly(3-hydroxybutyrate- co -3-hydroxyhexanoate) [P(3HB- co -3HHx)] was studied based on its copolymer composition determined by thermally assisted hydrolysis and methylation-gas chromatography (THM-GC). The change in copolymer composition of P(3HB- co -3HHx) film samples during soil burial degradation test was monitored in detail by THM-GC. As a result, the copolymer compositions of 3HB units gradually increased, while those of 3HHx units decreased with soil burial time, almost correlating with recovery weight. Based on these results, the biodegradation mechanism of P(3HB- co -3HHx) was elucidated with considering the influence of the crystallinity on the biodegradability. Furthermore, local differences in biodegradability of a given P(3HB- co -3HHx) film after soil burial test were also successfully evaluated from the copolymer compositions obtained by THM-GC. [ABSTRACT FROM AUTHOR]

Abstract: In our previous paper, thermally assisted hydrolysis and methylation-gas chromatography (THM-GC) measurements of poly(butylene succinate-co-butylene adipate) (PBSA) in the presence of tetramethylammonium hydroxide had revealed that the butylene adipate (BA) content in the PBSA films gradually decreased with soil burial degradation time. In order to clarify the cause of this change in copolymer composition, biodegradation behavior of PBSA with lowered crystallinity was evaluated by THM-GC. PBSA film samples with lower degree of crystallinity, prepared by heating and cooling quickly the original commercially available films, were subjected to a soil burial biodegradation test at 30°C for up to 4 weeks. The copolymer compositions between BA and butylene succinate (BS) units in various stages of the degraded film samples were estimated on the basis of chromatograms obtained by THM-GC with less than 5% of the relative standard deviations. As a result, the change in copolymer composition for the heated PBSA films during soil burial was relatively small compared to the original films, suggesting that biodegradation for the heated films proceeded with the comparable rate for both BA and BS-rich moieties due to lowered crystallinity. Based on these results, the reason for the change in copolymer composition observed for the original PBSA films was clarified as follows: (1) the BA-rich moieties in the copolymer chains could show relatively lower crystallinity than the BS-rich moieties and (2) the BA-rich moieties were preferentially biodegraded during soil burial test, leading to the decrease in the BA content as the biodegradation proceeded. [Copyright &y& Elsevier]

Abstract: Conventional methods used to analyze total fatty acids in wood generally require tedious and time-consuming pretreatments such as solvent extraction and hydrolysis of esterified fatty acids of fats. In this study, both total fatty acid composition and the yield from free and esterified fatty acids of fats in Acacia species were investigated using a rapid and direct method of thermochemolysis–gas chromatography (GC)–flame ionization detector (FID)/mass spectrometry (MS) with organic alkalis. Using tetrabutylammonium hydroxide (TBAH) at 300°C, thermochemolysis–GC–FID/MS gave total fatty acids including the fat origin as pyrolyzates with suppressed lignin fragment formation because of the basicity of TBAH compared to other organic alkalis: tetramethylammonium hydroxide and tetramethylammonium acetate. The obtained results of fatty acid composition were consistent with those obtained using conventional methods consisting of a series of procedures such as solvent extraction, hydrolysis, derivatization, and analysis by GC–FID/MS in fatty acid composition analysis. Furthermore, thermochemolysis–GC–FID gave a higher yield of total fatty acid than the conventional method, quantitatively reflecting the difficulty in solvent extraction of these components. Consequently, thermochemolysis–GC with TBAH promises to be a rapid and direct method to characterize total fatty acids in wood, avoiding artifacts by solvent extraction of wood. Furthermore, this method discriminated Acacia auriculiformis from Acacia mangium based on the observed fatty acid contents and selected individuals containing low total fatty acids to minimize paper sliding on a printer drum. [Copyright &y& Elsevier]

Abstract: Copolymer composition of a biodegradable aliphatic copolyester, poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (P(3HB-co-3HV)) with a wide range of 3HV contents (ca. 4–23mol%) was determined by pyrolysis-gas chromatography (Py-GC) in the presence of tetramethylammonium hydroxide (TMAH). Nine major peaks of methylated products, five of which were attributed to the products from 3HV unit and the other four from 3HB unit, were commonly observed in the pyrograms. The copolymer compositions of P(3HB-co-3HV) samples estimated based on the relative intensities of these peaks were consistent with those by 1H NMR. These results demonstrated that Py-GC in the presence of TMAH can be applied to the accurate and highly sensitive compositional analysis of P(3HB-co-3HV) using trace amounts (ca. 0.1mg or less) of the samples. Furthermore, the fact that a small amount (ca. 1%) of the pyrolyzate from 3HV unit was also observed on the pyrogram of a commercially available poly(3-hydroxybutyrate), PHB, suggested that the given PHB might be actually a copolymer containing minor amount of 3HV unit. [Copyright &y& Elsevier]

A novel rapid and sensitive method to characterize wood extractives in wood samples was developed on the basis of reactive thermal desorption-gas chromatography (RTD-GC) in the presence of an organic alkali, tetramethylammonium acetate ((CH3)4N+OCOCH3−, TMAAc) without using any cumbersome pretreatment such as solvent extraction. The RTD at 200 °C using TMAAc allowed highly sensitive detection of wood extractives such as fatty acid, phenolic acid and gallocatechin components in Eucalyptus camaldulensis as their methyl derivatives on the resulting chromatograms with suppressing the pyrolysis of the major wood constituent to the utmost. The fatty acid contents were able to be determined directly by RTD-GC using approximately 100 μg of the powdered wood samples with in relative standard deviations of 5%. The observed result was in fairly good agreement with that obtained by the conventional standard method including off-line transmethylation of acetone extracts followed by GC measurements. [Copyright &y& Elsevier]