NITROGEN-SPECIFIC DETECTION OF PEPTIDES IN LIQUID-CHROMATOGRAPHY WITHA CHEMILUMINESCENT NITROGEN DETECTOR

High-performance liquid chromatography with chemiluminescent nitrogen detection (HPLC-CLND) in the reversed-phase mode was used to quantitat e peptides that were isolated from casein hydrolysate. When CLND is us ed simultaneously with a UV detector in peptide mapping, unique quanti tative information about the nitrogen distribution of the sample is ob tained. Nitrogenous compounds without UV chromophores are easily detec ted by CLND without pre- or post-column derivatization. Of further sig nificance, the non-nitrogenous compounds in the sample matrix are tran sparent to the detector. This paper will focus primarily on the analys is of two peptides, identified as 1 and 2. The UV peptide map showed p eptide 2 as the largest component. On the other hand, the CLND results indicated that peptide 1 was the major peak. RP-HPLC amino acid analy sis of the peptides 1 and 2 confirmed the CLND results. This analysis shows that peptide 1 was the major component and did not contain aroma tic amino acid residues. Peptide 2 however, contained aromatic groups with strong chromophores, thereby explaining the UV response.