Chromatographic-mass spectrometric determination of free fatty acids in blood plasma and urine using extractive alkylation.

A method is proposed for the extractive alkylation of free fatty acids (FFA) in blood plasma and urine for their subsequent chromatographic-mass spectrometric determination as methyl esters. The list of target compounds includes 19 saturated acids (C-C) and 20 unsaturated acids (C-C), including ω-3, ω-6, ω-9, and polyunsaturated fatty acids. For the simultaneous extraction of FFA from a matrix and derivatization, extractive alkylation with iodomethane was used. The peculiarity and advantage of the method is integration of the stages of extraction and preparation of volatile derivatives under mild conditions. The recovery and conversion are from 60 to 90%. The analytical range was from 0.02 to 20 µg/mL of a sample. The effect of samples storage conditions on the results of measurements is evaluated. The method was tested in the determination of FFA in blood plasma and urine of volunteers and laboratory animals. [ABSTRACT FROM AUTHOR]