Suitable pretreatment method for the determination of amino acids and their D/L ratios in soil samples

An extraction method for amino acids in soil samples to determine their, concentrations and D/L ratios was developed. The amounts of amino acids extracted with a mixture of HF and HCl were much more than those extracted with hot water. Digestion of soil matrix with HF is necessary for extracting amino acids in soils. Since racemization of chiral amino acids occurred during extraction, different periods of HF extraction were employed to determine the initial D/L ratio. The extract was subjected to acid hydrolysis with 6 M HCl for 2 h to obtain free amino acids. The present procedure is promising to study amino acids in geological samples.