Due to the difficulties involved in the visual estimation of amino acids in
protein hydrolysates from serial dilutions on chromatograms a very simple photoelectric
method was devised to facilitate the accurate estimation of amino acid
concentration. Sources of errors which must be avoided are temperature fluctuations
of the chromatographic tank, non-uniform application of ninhydrin to the
filter paper, too high amino acid concentrations and discolorations of the filter
paper by organic solvents.
The method was applied to the analysis of silk fibroin and values were
obtained which agreed well with those determined by previous workers.