CONCERNING THE REINECKATE METHOD FOR THE DETERMINATION OF CHOLINE

Abstract

In the light of recent developments concerning the r6le of choline in nutrition and intermediary metabolism, the immediate need for a rapid quantitative chemical method for the determination of this substance is apparent.Most of the chemical methods employed to date have been based on the precipitation of choline as the reineckate, but other methods brought forth include the titrimetric determination of the trimethylamine formed by oxidative degradation of the choline (l-3), the precipitation of choline as the periodide with the subsequent liberation snd tit,ration of t,he iodine (4-7), and the determination of the mercury in the mercuric chloride double salt of choline (8, 9).An excellent recent review by Best and Lucas (10) includes a discussion of the estimat,ion of choline.Among the first to employ the reineckate method for the determination of choline were Bapfhammer and Bischoff (11) who dissolved the choline reineckate in acetone, evaporated the solvent, washed the residue with ether, and weighed it after drying.Greater sensitivity was obtained by Beattie (12) who, by subjecting the pink acetone solution of choline reineckate to calorimetry, could estimate around 0.3 mg. of choline in a concentration of 0.003 per cent with a maximum error of 3 per cent.Jacobi, Baumann, and Meek (13), Thornton and Broome ( 14), and Engel (15) applied photoelectric calorimetry to the acetone solution.The development of a brown color, by adding an iodine reagent to an aqueous solution of choline reineckate, was used as the basis of a method by Shaw (16).Later Marenzi and Cardini (17) described a calorimetric procedure in which the choline reineckate is oxidized by alkaline hydrogen peroxide and then treated with diphenylcarbazide in acid solution to yield a violetred color (Cazeneuve's reaction for chromate).The authors claim this method will allow the estimation of as little as 15 y of choline.For ordinary purposes, the met,hod depending on photoelectric measurement of the color int,ensity of the acetone solution of the reineckate is as good as any in current use.Since this method has the advantages of simplicity and speed, the present communication will deal with an examination of the steps in the procedure and certain improvements that have been effected during the course of this investigation.