High-performance liquid chromatography intercomparative study for amino acid analysis in two tissues by PITC- and OPA-derivatizations

In this paper, we have extensively investigated the pre-column derivatization method with o-phthaldialdehyde (OPA) to analyze cysteine, cystine, among with other 18 amino acids, using reversed-phase high-performance liquid chromatography analysis (RP-HPLC), and after we have compared it with an other method involving phenylisothiocyanate (PITC) in order to have a two sensitive methods to use accordingly the matrix. We have studied the analytical conditions for the OPA-reaction together with precision, linearity range, correlation coefficient (>0.998) and limit of detection (between 14 fmol and 1 pmol) for each amino acid. Then, we have applied the two methods to the analysis of larynx and kidney tissues: between the two methods, the amino acid recoveries (between 80% and 100%) and the correspondence of the OPA and PTC results are satisfactory considering the different involved derivatization procedures. PTC- and OPA-chromatograms obtained in the analysis of actual samples are reported together with the amino acid level, with particular regard to the cysteine/cystine determination.