DETERMINATION OF PROTEIN AMINO-ACIDS AS BUTYLTHIOCARBAMYL DERIVATIVES BY REVERSED-PHASE HIGH-PERFORMANCE LIQUID-CHROMATOGRAPHY WITH PRECOLUMN DERIVATIZATION AND UV DETECTION

Twenty-two protein amino acids were derivatized to butylthiocarbamyl derivatives by precolumn reaction at 40 degrees C for 30 min with butyl isothiocyanate. All of the derivatives were quantitatively resolved in 27 min by RP-HPLC on a Nova-Pak C-18 column and detected at 250 nm with a UV detector. Asparagine and serine were resolved in a single peak. The relative standard deviations of the relative molar responses with respect to the methionine peak were less than 5% for all of the derivatives except cysteine. The calibration graphs showed good linearity in the range 0.5-2.5 nmol. Correlation coefficients for all of the calibration graphs were highly significant (p < 0.001). The stability of the derivatives at room temperature was about 8 h.