Extraction and derivatization of some short chain fatty acids and their determination in fruit juices and fermented dairy products using gas chromatography

Abstract

Introduction: An in-situ dispersive liquid-liquid microextraction and derivatization method based on deep eutectic solvent has been developed for the analysis of five short chain fatty acids (as model compounds) in different beverage samples prior to their determination by gas chromatography-flame ionization detection. Actually an air-assisted liquid-liquid microextraction method followed by gas chromatography-flame ionization detection was developed for the extraction, derivatization, and determination of five short chain fatty acids including acetic acid, propionic acid, butyric acid, valeric acid, and caproic acid in different fruit juices. Expression of purpose: In this method, butyl chloroformate is used as extraction solvent and derivatization agent, simultaneously. Method: For this purpose, sample solution is adjusted at pH=8 and then mixed with picoline (as a catalyst). Then, a few microliters of butyl chloroformate is added and after performing predetermined extraction cycles, the obtained cloudy solution is centrifuged. The analytes are derivatized and extracted into the fine droplets of extracting agent, simultaneously. An aliquat of the sedimented phase is injected into the determination system. Results: Low limits of detection (3.2-9.6 ng mL-1) and quantification (10.8-32.4 ng mL-1) was obtained. Discussion and conclusion: The developed method was successfully used in determination of the analytes in different beverage samples.The method had a proper repeatability (RSDs≤7.4%) for intra- (n=6) and inter-day (n=5) precisions at a concentration of 50 ng mL-1 of each analyte, and high enrichment factors (360-415) extraction recoveries (72-93%), and enhancement factors (1126-1852). In this method, for the first time, a disperser solvent was simultaneously used as derivatization agent in DLLME. Under the optimum conditions, the obtained data indicated that the method has low LODs and LOQs, high EFs and ERs and short extraction time.