Microdetermination of fatty acids by gas chromatography
1973 Volume 22 Issue 7 Pages 872-875
Details
1973 Volume 22 Issue 7 Pages 872-875
Analytical method of fatty acids in a microgram scale was studied.
Fatty acid in amount of 10100μg in aqueous solution was quantitatively extracted by three times each for 2 min with diethyl ether in a separation funnel by hand. The extractant was dried over anhydrous sodium sulfate over a night. Then the dried extractant was distilled at 4045°C in a water bath to almost dryness.
Fatty acids were methylated with diazomethane for gas chromatography. A small amount of diazomethane was prepared according to the method of Schlenk et al., and bubbled into methanol-diethyl ether (1: 9 v/v) up to saturated with it.
The dry residue was treated with an excess of methanol-ethereal diazomethane at room temperature for 30 min, followed to heat at 4045°C in order to remove an excess diazomethane.
Methyl derivatives were eluted in 22 min using temperature programming from 90°C to 230°C at rate of 7.5°C/min on a glass column 4 ft×1/4 in (o. d.)containing 2.5% stabilized PEGA on Diasolid M (6080 mesh). Concentration was calculated by comparing the peak heights. Calibration curves were linear for each acid in the range of 5 to 100 ppm. The relative standard deviations for the peak heights of fatty acid methyl esters with temperature programming were within 3%.
Recovery of more than 90% was obtained at esterification of fatty acid using diazomethane, but lower for C8 and C10 acids, because some loss was observed for their volatility at the removal of an excess diazomethane. Recovery of more than 90% for fatty acid was obtained at extraction from the acidic solution (concentration of less than 1 ppm).
A 2.5% FFAP column was used for identification of fatty acid to the sample which were observed many peaks on a chromatogram, and a 10% PDEGS column was used to separate saturated and unsaturated fatty acids.
In the case of microanalysis, it was necessary before use to remove the impurities contained in diethyl ether, distilled water, sulfuric acid and anhydrous sodium sulfate used at extraction.
