A rapid and sensitive colorimetric microdetermination of free and bound choline

✍ Scribed by C. J. F. Böttcher; C. Pries; C. M. van Gent

• Publisher: Elsevier Science
• Year: 2010
• Tongue: English
• Weight: 400 KB
• Volume: 80
• Category: Article
• ISSN: 0165-0513
• DOI: 10.1002/recl.19610801102

✦ Synopsis

Abstract

The colorimetric estimation of quaternary ammonium bases with the aid of cis‐aconitic anhydride ^6^ has been shown to be applicable to choline, and is superior in sensitivity and reproducibility to the usual precipitation methods for determining this substance. It can be applied to substances containing choline, e.g. some of the phospholipids, without the necessity of first liberating free choline by hydrolysis. For this purpose the colour must be developed for a longer time and at a higher temperature than formerly described, until the initial red‐purple colour changes through violet to green. The optimum wavelengths for determining the extinction of the red‐purple and green solutions are 515 and 530 mμ respectively.

The intensity of the green colour is linear with concentration over the concentration range 0.3‐5 μg quaternary nitrogen (N4) (= 3‐50μg choline, 20‐300 μg lecithin). The extinction per μg N4 is 0.110 for a light‐path of 1 cm and a final solution volume of 8 ml, and linearity is preserved if the solution is diluted after development of the colour. Both reproducibility and accuracy of the estimation are within ± 4%.