title: Determination of choline in milk and infant formulas by enzymatic analysis: collaborative study.
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 micrograms/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.
authors.affiliation: AgriQuality NZ Ltd., Auckland, New Zealand.
authors.forename: D C
authors.initials: DC
authors.lastname: Woollard
authors.forename: H E
authors.initials: HE
authors.lastname: Indyk
mesh_terms: D000429:Alcohol Oxidoreductases / Q000378:metabolism; D000675:Ampyrone; D000818:Animals; D002138:Calibration; D002794:Choline / Q000032:analysis*; D004798:Enzymes; D006801:Humans; D006863:Hydrogen-Ion Concentration; D006868:Hydrolysis; D007225:Infant Food / Q000032:analysis*; D007753:Laboratories / Q000592:standards; D016014:Linear Models; D008892:Milk / Q000737:chemistry*; D009195:Peroxidase / Q000378:metabolism; D019800:Phenol; D010740:Phospholipases / Q000378:metabolism; D011786:Quality Control; D012015:Reference Standards; D012680:Sensitivity and Specificity; D013053:Spectrophotometry
chemical_list: D004798:Enzymes; D000675:Ampyrone; D019800:Phenol; D000429:Alcohol Oxidoreductases; C019888:choline oxidase; D009195:Peroxidase; D010740:Phospholipases; D002794:Choline