70 Studies on Phospholipids 3 . DETERMINATION OF CHOLINE

Micromethods for the determination of choline have been described by Beattie (1936) and Glick (1944). Both procedures involved the use of Reinecke salt as a precipitant, required 20150 pmoles of choline and depended on measurement of the pink colour of an acetone solution of the precipitate. More sensitive modifications of the reineckate method depend upon measurement of the chromium content of the precipitate (Marenzi & Cardini, 1943) or the absorption at 328 mye (Winzler & Meserve, 1945). The use of potassium periodide as a choline precipitant was described first by Stanek (1905) and has since been modified by Erickson, Avrin, Teague & Williams (1940) and by Appleton, La Du, Levy, Steele & Brodie (1953). Levine & Chargaff (1951) have described a semiquantitative method involving chromatography on paper and subsequent treatment with phosphomolybdic acid. Choline shows up as a yellow spot which may be reduced with stannous chloride to give a blue colour. The reaction between choline and phosphomolybdic acid has been investigated and this paper presents the results obtained and provides details of a method for the microdetermination of choline.