PubMed · 7321549
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E H Foerster, J C Garriott. Analysis for volatile compounds in biological samples.. https://doi.org/10.1093/jat%2F5.5.241
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A simple, reproducible, and rapid gas chromatographic method for short-chain fatty acid determination in human feces was developed. It involves direct injection of fecal supernatants into the gas chromatograph, without any pretreatment. Contamination of the gas chromatographic column with nonvolatile fecal material was prevented by the use of a glass liner in the injector. This liner, which acted as a precolumn, was stoppered with a glass wool plug at the lower end of the liner. Injection was performed against the glass wall of the liner, ensuring an immediate contact of the injected sample with the hot glass wall. More than 100 injections of fecal supernatants could be carried out before the liner had to be replaced by a new one. Peak tailing and ghosting was prevented by the use of formic acid in the fecal samples. The method gave sharp peaks with baseline separation for all the fatty acids.
We devised a sensitive and simple method for determining cyanide and its major metabolite, thiocyanate, in blood using an extractive alkylation technique. Pentafluorobenzyl bromide was used as the alkylating agent, and tetradecyldimethylbenzylammonium chloride was used as the phase-transfer catalyst. The derivatives obtained were analyzed qualitatively by gas chromatography-mass spectrometry and quantitatively by gas chromatography with an electron-capture detection. The detection limits of cyanide and thiocyanate were 0.01 and 0.003 mumol/ml, respectively, while the gross recovery of both compounds was 80%. The calibration curve was linear over the concentration range from 0.02 to 1.0 mumol/ml for cyanide and from 0.01 to 1.0 mumol/ml for thiocyanate. The accuracy and precision of the method were evaluated, and the coefficients of variation were found to be within 10%. Using the method, the blood levels of two victims who had died from cyanide poisoning were determined.
The alcohol-insoluble substance (AIS) from red beet (Beta vulgaris var. conditiva Alef.) (3.31% of the edible substance) was extracted sequentially with water, ammonium oxalate, 0.05 N HCl and 0.05 N NaOH. Accordingly 3.93 g, about 0.8 g, 2.96 g resp. 3.80 g galacturonan/100 g AIS were extracted with this procedure. These pectin extracts were purified as Cu2 +-salts and fractionated into a water-soluble and a water-insoluble part. The composition of neutral monosaccharide units was estimated in the fractions. Gal, Ara and Glc dominated; Xyl, Rha and Man were also present but in smaller amounts. A higher GalA content was found in the soluble fractions (with the exception of the alkali extract). Pectins from red beet are middle- or low-esterified and partially acetylated. The composition of the AIS and of the residue after pectin extraction (RE) was determined (14.6 resp. 9.5% pectin; 10,6 resp. 17.6% protein; 58.7 resp. 64.9% total polysaccharides). In the AIS 23.3% soluble and 54.7% insoluble dietary fiber were estimated, whereas in RE 15.3 resp. 54.7% were found (enzymatic method). Following dietary fiber fractions were determined by the detergent method for both preparations: 39.0 resp. 52.7% NDF; 6.3 resp. 4.5% NDF filtrate; 23.6 resp. 41.8% ADF; 1.2 resp. 1.8% lignin. The water binding capacity decreased from 19.85 g water (AIS) to 11. 53 g water (RE) related to 1 g AUS. From these just 50% were found in the NDF fractions and about 13% in the ADF fractions. Alterations of the grown biological structures during pectin extraction and dietary fiber analysis (detergent method) were investigated by scanning electron microscopy.