title: Quantitation of major choline fractions in milk and dietary supplements using a phospholipase d bioreactor coupled to a choline amperometric biosensor.
abstract: Current analytical methods lack the capacity of simultaneous determination of the content of free choline and phosphatidyl-bound choline, mainly phosphatidyl choline, in raw milk. Quantitative determination of total, free, and phosphatidyl-bound choline in milk and a dietary supplement is described using a phospholipase D packed bioreactor coupled to a choline oxidase-based amperometric biosensor. The response for choline and phosphatidyl choline was linear up to 0.5 mM and 1 mM, respectively, and the detection limits were 0.02 and 0.03 mM, respectively. The conversion efficiency of phosphatidyl choline to choline was 50% at 0.2 mL min(-1). The within days coefficient of variation for choline and phosphatidyl choline determination in milk samples was 2.8% and 3.2%, respectively. With the addition of an acid hydrolysis step, the method can quantify the concentrations of total, free, phosphatidyl-bound, and non-phosphatidyl-bound choline esters, thus permitting determination of major choline fractions in a complex matrix.
authors.affiliation: Dipartimento di Chimica, Università di Bari, Via Orabona, 4, 70126 Bari, Italy.
authors.forename: S
authors.initials: S
authors.lastname: Pati
authors.forename: F
authors.initials: F
authors.lastname: Palmisano
authors.forename: M
authors.initials: M
authors.lastname: Quinto
authors.forename: P G
authors.initials: PG
authors.lastname: Zambonin
mesh_terms: D000818:Animals; D019149:Bioreactors; D015374:Biosensing Techniques; D002794:Choline / Q000032:analysis*; D019587:Dietary Supplements / Q000032:analysis*; D004800:Enzymes, Immobilized; D008892:Milk / Q000737:chemistry*; D010713:Phosphatidylcholines / Q000032:analysis; D010739:Phospholipase D
chemical_list: D004800:Enzymes, Immobilized; D010713:Phosphatidylcholines; D010739:Phospholipase D; D002794:Choline