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 especially of cysteine in musts and wines is reported. This technique involves the use of a pre‐column derivatisation with iodoacetic acid (IDA) and o‐phthaldialdehyde (OPA). Isoindole‐type fluorescent derivatives were formed in alkaline solution from OPA, 2‐sulphanylethanol and the primary amine group of the amino acids. The derivatives were separated by HPLC using a linear multistep solvent gradient and were detected by spectrofluorimetry. This method is suitable for the separation of most free amino acids including cysteine. It allows high recovery and satisfies the necessary requirements with respect to accuracy, repeatability and sensitivity. The first application of this analytical method to the measurement of cysteine in musts and wines is reported. © 2001 Society of Chemical Industry