Removal of acid by trioctylamine from samples for microbiological assay

Abstract

Histidine can be estimated by microbiological assay in aqueous extracts of tissues from which trichloroacetic acid has been removed by shaking with a chloroform soln. of trioctylamine according to Lester Smith and Page, provided that the extraction is followed by further extractions with chloroform and ether. These are necessary to remove inhibitory effects due to the retention of traces of trioctylamine in the aqueous phase. Histidine values for the blood of cat, rabbit, and man and for gastric mucosa and striated muscle of rabbit, cat and toad are given. Histidine in striated muscle increased about 20-fold on heating the soln. with acid, presumably owing to the hydrolysis of carnosine.