Simultaneous determination of choline and betaine in some fish materials

Abstract

The assay of choline and betaine, as water-insoluble reineckate derivatives, has been adapted to the simultaneous determination of these two quaternary nitrogenous compounds. No preliminary column fractionation is required. The solution resulting from the initial extraction - hydrolysis stage is divided into two portions; one portion is adjusted to pH 1.0 and the other to pH 8–9 before the addition of ammonium reineckate. Under acidic conditions, choline and betaine reineckate are precipitated and at an alkaline pH only choline reineckate precipitates. The reineckate salts are re-dissolved in acetone to give pink solutions for spectrophotometric measurement at 526 nm. Choline reineckate has a higher linear absoptivity than betaine reineckate and this feature is allowed for by reference to the respective calibration graphs; the choline content of the extract is determined directly and the betaine content by difference. Model systems containing 2–3 mg of pure choline or betaine can be assayed but sample masses of 3–4 g of biological material are recommended for the analysis.