Rapid enzymatic method for the determination of phosphoryl choline using the fluorescence of the enzyme choline oxidase. Sequential determination of choline and phosphorylcholine in milk powder for children

In this paper we present a rapid method for determining phosphorylcholine (ChoP). ChoP was first hydrolysed by the enzyme alkaline phosphatase (AP); the choline formed was then submitted to a reaction with Choline Oxidase (ChOx). Both reactions were carried out simultaneously, in the same test without previous steps of incubation. The analytical signals used were the intrinsic fluorescence of ChOx due to FAD and that corresponding to a fluorescein derivative bonded to ChOx (ChOx-FS); both can be related with the concentration of ChoP. Once the conditions were optimized, the response range for ChoP was 5.2×10−7–1.0×10−5M using the peak area as the analytical parameter with a precision of about 4% (RSD) at both ChOx and ChOx-FS wavelengths.