Densitometry for analysis of protein and peptide hydrolysates: application to luteinizing hormone releasing hormone

Densitometric analysis has been performed on various standard protein and peptide solutions and on luteinizing hormone releasing hormone hydrolysate. After thin-layer chromatographic separation using two-dimensional separation on cellulose plates, the plates were mapped and each amino acid was assayed individually in order to obtain a specific integration profile of the hydrolysate. Densitometry proved to be a useful method for the screening of protein hydrolysates and is accurate enough for the assay of peptide hydrolysates. The hormone was hydrolysed with hydrochloric acid-trifluoroacetic acid (1:1, v/v) in the presence of thioglycolic acid. This limits the loss of tryptophan and does not interfere with the analysis. Results were sufficiently reliable, accurate and reproducible for routine analysis.