Determination of Choline in Milk and Infant Formulas by Enzymatic Analysis: Collaborative Study

Abstract

Abstract A collaborative study was conducted on a coupled enzymatic–spectrophotometric method for the determination of choline in infant formula and milk powders. Twenty-nine laboratories participated in the analysis of 8 blind duplicates over the range of 45–175 mg/100 g sample. After the combined acid hydrolysis–phospholipase release of choline, incubation with choline oxidase in the presence of peroxidase and phenol generates a quinoneimine chromophore with 4-aminoantipyrine. Following raw data screening, overall mean RSDR was estimated at 5.14% (range, 4.26–6.34%) with a HORRAT value of 0.91 (range, 0.76–1.00) and an overall mean RSDr:RSDR value of 0.53 (range, 0.42–0.74). The method was also compared with alternative independent analytical techniques for several of the collaborative study samples.