Method of determination of some aromatic acids in soil solution from paddy fields by gas chromatography-mass spectrometry

Abstract

Abstract A simplified method for the determination of benzoic 2-phenylpropionic, 3-phenylpropionic, and 4-phenylbutyric acids in paddy field soils using a gas chromatograph-mass spectrometer equipped with a capillary column is described. The entire procedure of this method involves the collection of the soil solution, extraction with chloroform, methylation of the acids with diazo- methane and analysis by gas chromatography-mass spectrometry. In this method, extracts were prepared by shaking the soil solution with chloroform at room temperature for 60 min. The use of a chloroform extractant instead of ether enabled to omit the procedure for the removal of water after the extraction process. This method showed a high sensitivity and high selectivity in the analysis of the aromatic acids dissolved in the soil solution. The sample of soil solution collected through a porous cup was concentrated on a hot plate and extracted with chloroform after acidification. Aromatic acids in a dilute solution whose concentration was 1X 10-7 could be determined with a volume of soil solution less than 6 ml. Application of this method to the analysis of aromatic acids in the soil solution showed that the method was accurate enough to enable the evaluation of their inhibitory effect on the growth of rice roots.