Trimethylsilylated residue, analysis

Glycosyl-residue compositions were determined by GC-CIMS analysis of the per-O-trimethylsilylated methyl glycosides [23] separated on a fused-silicaDB-1 capillary column. The identity of each peak was confirmed by CIMS on a HP-5989 MS Engine (Hewlett-Packard). 

After evaporation of the alcohol, the trimethylsilyl ether was prepared by dissolving the residue or the standard acid (after methylation) in 0.2 cm3 of dioxane, 0.2 cm3 of hexamethyldisila-zane, and 0.1 cm3 of trimethylchlorosilane and mixing thoroughly. The preparation in a 2-cm3 test tube with Teflon lined cap was left for 30 min at room temperature. After centrifugation, 0.5 pi of the supernatant can be injected into the gas chromatographic instrument. The derivatives are stable if kept in a desiccator. It is recommended that the analysis be carried out the same day. 

The presence of residual THF in the final product is easily detected by the characteristic NMR signals at 6 1.85 (4 H) and 3.75 (4 H). The checkers found GLC to be more convenient than 1H NMR for analysis at this point. Either a 6 x 2 mm glass column of 3% 0V-101 on MHP 80/100 with 30 nt/min He or a 15 m x 0.25 mm fused silica capillary column of DB-5 (cross-linked phenyl silicone) with 1 mL/min H2 proved sufficient to resolve butane, trimethylsilylacetylene, butyltrimethylsilane, THF, 1-chlorobutane, and b1s trimethylsilyl)acetylene. 

The aqueous residue of the acid hydrolysed flavone glycoside could either be identified by paper or thin layer chromatographic analysis by comparing with the standard samples or after preparing their trimethylsilyl derivatives they were subjected gas chromatographic separations, and measuring the retention times will let us know the identity of the sugars [4, p.24-32],... 

GC-MS analysis is an indirect method to detect TTX in a crude extract which is difficult to purify for other advanced analysis. In this method, TTX and its derivatives (0.2 ml with 25 MU) are dissolved in 2 ml of 2 mol/liter NaOH and heated in a boiling water bath for 45 minutes. After being cooled at room temperature, the alkali-decomposed compounds are adjusted to pH 4.0 with 1 mol/liter HCl and extracted thrice with three volumes of 1-butanol. The extracts are combined and evaporated to dryness in vacuum, and to the residue is added a mixture of N,0-bis acetamide, trimethylchlorosilane, and pyridine (2 1 1), in order to derive trimethylsilyl (TMS) Cg-base compounds. The derivatives are then submitted to GC-MS analysis. The column temperature is maintained from 180 to 250° C at a rate of 5°C/minute. The flow rate of inlet helium carrier gas is maintained at 20 ml/minute. The ionizing voltage is usually kept at 70 eV with the ion source temperature at 200°C. 

Preparation of methylboronate esters-trimethylsilyl ethers [131] Methaneboronic acid (I molar proportion) in dry pyridine was added to the steroid diol (100 jUg) and the mixture was kept at 60 °C for 30 min. Silylation was carried out after removal of the solvent by treating the methylboronate with BSTFA (5/ll) and heating at 60 °C for 2 min or with BSTFA in DMF (20 fi, 1 3 v/v) for 60 for 5 min. The solution was evaporated to dryness and the residue was dissolved in ethyl acetate for GC and GC--MS analysis. 

It is also possible to perform GLC on the trimethyl-silyl ethers of the sterols. In that case, the residue is gently heated with a mixture of dimethylformamide, hexamethylsilazane and trimethylchlorosilane to prepare the trimethylsilyl ethers. The gas chromatographic method described provides a qualitative analysis of sterols in oils and fats. However, it can be employed for quantitative analysis within certain limitations (a) the response of each sterol is a function of the type of detector used (b) an accurate quantitative interpretation of the chromatogram... 

A gas chromatographic method may be employed for analysis for both benzoic acid and sorbic acid in food, as described in AOAC method 983.16. The acids are extracted from an acidified aqueous homogenized food sample into ether. The acids are then extracted from the ether solution into aqueous alkali, and after acidification they are re-extracted into dichloromethane. Treatment of the residue with N-methyl-N-trimethylsilyltrifluoroacetamide converts the benzoic and sorbic acids into trimethylsilyl esters. These esters are then analyzed with a glass column packed with a support coated with OV-1, in a temperature programmed analysis. Phenylacetic and caproic acids are used as internal standards for benzoic and sorbic acids, respectively. An LC method has also been described for analysis of benzoic acid with simultaneous determination of sorbic acid, and methyl, ethyl, propyl, and butyl p-hydroxybenzoates. The preservatives were extracted from meat or seasonings with 70% ethanol, and analyzed by reversed-phase LC using a Cig stationary phase with a linear gradient from 10 to 70% methanol in 1.5% aqueous ammonium acetate and 1.5% aqueous acetic acid. 

Methods for the GC analysis of the fumonisins require the hydrolytic removal of the two very polar tricarboxylic acid residues and subsequent trimethylsilylation of the several hydroxyl groups and amino acid groups present in the parent molecule. Ideally confirmation with GC-MS is still desirable but only available in a very limited number of laboratories. 

A coryneform bacterium growing on either D-glucose or soluble starch synthesized a viscous polysaccharide (mol. wt. 2.5 x 10 ) composed of residues of D-mannose, D-galactose, o-glucose, o-glucuronic acid, and pyruvate (molar proportions 1 1 1 3 1). The non-Newtonian flow and dynamic viscoelasticity of the polysaccharide resemble those of guar gum. Analysis (g.l.c.-m.s.) of the products obtained on methanolysis, N-acetylation, and either 0-trimethylsilylation or 0-acetylation of partially methylated colominic acid (an extracellular polysaccharide from E. coli) has confirmed that adjacent AT-acetylneuraminic acid residues are (2 8)-linked. ... 

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