Ultra-microdetermination of Arginine by a Compound Microbiological Assay Method.

Abstract

The sensitivity of a microbiological assay method may be compounded by employing secondary microbiological assay to determine the D-lactic acid component of the products obtained from the response of the original assay. Sensitivities of up to several thousand times those realized by the standard microbiological procedures were possible theoretically in compound assays. The method descr. for the compound assay of arginine, designed purposely to be of relatively low sensitivity, was approx. 144 times as sensitive as the standard microbiological method. The avg. percentages of arginine found in casein (3.49%), gelatin (9.04%), and silk fibroin (1.02%, respectively, by the compound assay were approx. the same as those (3.67%, 8.78%, and 1.02%, respectively) by the standard method. The sample wts. required per assay (each including triplicate detns. at each of 4 or 5 sample levels) were: casein 45 [mu]g., gelatin 18 [mu]g., and silk fibroin 142 [mu]g. One hundred times these amts. were required for each assay by the standard microbiological method.