Substances in the Calf Alimentary Tract interfering in the Determination of Polyethylene Glycol

Abstract

THE water-soluble polyethylene glycols of high molecular weight promise to be of great value as reference substances in the study of exchange processes in the alimentary canal. In particular, a mixture of such polymers with a molecular weight of about 4,000 appears to pass largely unchanged and unabsorbed through the alimentary tract in sheep, humans, hens, cows and calves^1,2. Polyethylene glycol can readily be determined turbidimetrically, once interfering substances have been removed, after precipitation with trichloracetic acid solution containing barium chloride^2,3. We found, in agreement with Hydén³, that an initial treatment with barium hydroxide, zinc sulphate and barium chloride sufficed to remove interfering substances (mainly protein and sulphate) from milk and from calf rumen contents, urine and faeces extracts. The method failed, however, in two respects when it was applied to samples from fistulas in the small intestines of milk-fed calves.