Rapid determination of primary amino acids in grape juice using anULo/UL-phthaldialdehyde/N-acetyl-L-cysteine spectrophotometric assay.

摘要

This assay is based on the derivatization of primary amino groups with an o-phthaldialdehyde/N-acetyl-L-cysteine (OPA/NAC) reagent. The resulting isoindole derivatives formed rapidly and were stable at a wavelength of 335 nm. The procedure used a juice blank to account for the absorbance of non-derivative forming compounds in the juice. The assay was insensitive to proline, showed a 3.5% response to ammonium and correlated with HPLC estimates (R2 = 0.988). The relative standard deviations for replicated analyses ranged from 0.27 to 3.20%. Estimates made using this procedure were within the systematic errors for model solutions, and known additions of isoleucine to grape juices had recoveries of 97.6-101.3%. The relative accuracy, precision, rapidanalysis times and use of low-toxic reagents suggest that this procedure is appropriate for use in wineries.