Search

A highly sensitive method to analyze the intact lipids in a single zooplankter individual at the level of a few tenths of a microgram was developed by matrix-assisted laser desorption/ionization mass spectrometry (MALDI-MS) combined with a direct sampling technique. The sampling procedure involved (1) putting a zooplankter individual sample onto the MALDI sample plate, (2) cutting the sample into a few pieces by means of tweezers, (3) depositing aliquots of matrix and cationization reagent solutions on the zooplankter sample, and (4) irradiating with a [N.sub.2] laser to cause MALDI. By using this technique, the mass spectra of the single zooplankter samples showed a series of ions generated from phospholipids with 34 or 36 carbons in the acyl groups and neutral lipids such as triglycerides and diacylglyceryl ethers with 50-54 carbons in their acyl and alkenyl groups. Accordingly, this method enabled us to estimate the relative quantity between 'structured lipids' (phospholipids) and 'storage lipids' (neutral lipids) in an individual zooplankter, which should give us a good clue to elucidate the roles of each class of lipids in its growth.

The combination of evolved gas analysis, trap-and-purge sampling of desired portions of the evolved fraction (heartcutting), and gas chromatography-mass spectrometry characterization (GC-MS) can be a very powerful method to investigate [...]

The combination of evolved gas analysis, trap-and-purge sampling of desired portions of the evolved fraction (heartcutting), and gas chromatography-mass spectrometry characterization (GC-MS) can be a very powerful method to investigate [...]

Detailed quantitative analysis of lignin monomer composition comprising p-coumaryl, coniferyl, and sinapyl alcohol and p-coumaraldehyde, coniferaldehyde, and sinapaldehyde in plant has not been studied from every point mainly because of artifact formation during the lignin isolation procedure, partial loss of the lignin components inherent in the chemical degradative methods, and difficulty in the explanation of the complex spectra generally observed for the lignin components. Here we propose a new method to quantify lignin monomer composition in detail by pyrolysis-gas chromatography (Py-GC) using acetylated lignin samples. The lignin acetylation procedure would contribute to prevent secondary formation of cinnamaldehydes from the corresponding alcohol forms during pyrolysis, which are otherwise unavoidable in conventional Py-GC process to some extent. On the basis of the characteristic peaks on the pyrograms of the acetylated sample, lignin monomer compositions in various dehydrogenative polymers (DHP) as lignin model compounds were determined, taking even minor components such as cinnamaldehydes into consideration. The observed compositions by Py-GC were in good agreement with the supplied lignin monomer contents on DHP synthesis. The new Py-GC method combined with sample preacetylation allowed us an accurate quantitative analysis of detailed lignin monomer composition using a microgram order of extractive-free plant samples.

A method to determine chemical composition of natural resin shellac was developed on the basis of reactive pyrolysis-gas chromatography (Py-GC) in the presence of an organic alkali, tetramethylammonium hydroxide ([(C[H.sub.3]).sub.4]NOH, TMAH). Py-GC using 25% TMAH aqueous solution enabled the highly sensitive determination of terpenic acids, aleuritic acid, several minor fatty acids, and the wax components of shellac as their methyl derivatives on the resulting pyrograms with less than 2.0% relative standard deviations without using any cumbersome pretreatment. The observed average distributions of each resin acid component determined by reactive Py-GC for shellac samples from India and Thailand showed that the average ratios among terpenic acids, aleuritic acid, and the other fatty acids were about 53:34:14 for Indian shellac and 51:35:14 for Thailand shellac, respectively, suggesting a slightly significant difference. However, clearer discrimination of the shellac samples from the two different growing places was attainable by applying principal component analysis for the mole percent distributions of all the acidic components determined by reactive Py-GC.

A new method to determine directly and rapidly the degree of acetylation of chitin/chitosan was developed based on reactive pyrolysis-gas chromatography in the presence of an oxalic acid aqueous solution. The degree of acetylation was precisely evaluated on the basis of peak intensities of the characteristic products such as acetonitrile, acetic acid, and acetamide originating from the N-acetyl group of N-acetyl-D-glucosamine units of chitin/chitosan. The observed values were in good agreement with those obtained by 1H NMR and the other methods. Moreover, the proposed technique was applicable to any kinds of chitin/chitosan samples over the whole range of acetylation including insoluble chitin/chitosan and perfectly acetylated artificial chitin having higher crystallinity to which 1H NMR had been inapplicable.

The end groups in poly(methyl methacrylate) (PMMA) macromonomers and their radically polymerized prepolymers were determined using a pyrolysis gas chromatograph (Py-GC) equipped with a simultaneous multidetection system. End groups associated with the initiator azobis(isobutyronitrile) (AIBN) and the chain transfer reagents such as thioglycolic acid and mercaptopropionic acid were of particular interest. Various characteristic pyrolyzates that reflected the end groups in the PMMAs were observed on the pyrograms. Pyrolysates that contain sulfur from the chain transfer reagent residues in the end groups were determined on the basis of the pyrograms simultaneously obtained by a sulfur-selective flame photometric detector and an ordinary flame ionization detector (FID). On the other hand, the cyano-group-containing end groups consisting of the AIBN residue were determined from the pyrograms simultaneously observed by FID and a nitrogen-phosphorus detector. The degree of polymerization estimated from the relative intensities of the end-group-specific pyrolyzates were comparable with those determined by size exclusion chromatography (SEC). Furthermore, the terminal ratio estimated by Py-GC proved to be in good agreement with those calculated from kinetic data.

Styrene copolymer sizing agents in paper are determined by pyrolysis gas chromatography. Styrene monomer derived from the styrene sequences in the copolymer is used as the key product in the pyrograms of paper samples. The amounts of the sizing agents retained in paper samples are determined with a precision of about 1.4% relative standard deviation. The results obtained suggest that about 80% of the sizing agents added in the pulp slurry are retained in the paper samples studied. Furthermore, the amounts of the sizing agents in paper are interpreted in terms of the degree of sizing.