Determination of the chloride content of small muscle samples

Abstract The chloride content of fat-free dry muscle tissue can be determined by dilute nitric acid extraction or alkaline digestion followed by titration with silver ions. If the sample of tissue weighs less than 30 mg a significant exponential relationship is found between the chloride content and sample size. Evidence is presented to suggest that free sulphydryl groups are present in varying amounts in extracts of fat-free dry muscle samples weighing less than 30 mg. These combine with silver ions in a reaction similar to that between silver and chloride ions and this effect accounts for the relationship between chloride content and sample size. This relationship is not observed if alkaline digestion is followed by perborate oxidation, or if chloride is measured by microdiffusion analysis instead of by silver ion titration.