Automated HPLC method for the measurement of free amino acids including cysteine in musts and wines; first applications

An analytical method for the determination of free amino acids and especial ly of cysteine in musts and wines is reported. This technique involves the use of a pre-column derivatisation with iodoacetic acid (IDA) and -phthaldi aldehyde (OPA). Isoindole-type fluorescent derivatives were formed in alkal ine solution from OPA, 2-sulphanylethanol and the primary amine group of th e amino acids. The derivatives were separated by HPLC using a linear multis tep solvent gradient and were detected by spectrofluorimetry. This method i s suitable for the separation of most free amino acids including cysteine. It allows high recovery and satisfies the necessary requirements with respe ct to accuracy, repeatability and sensitivity. The first application of thi s analytical method to the measurement of cysteine in musts and wines is re ported. (C) 2001 Society of Chemical Industry.