Determination of choline in milk, milk powder, and soy lecithin hydrolysates by flow injection analysis and amperometric detection with a choline oxidase based biosensor |
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| Authors: | Pati Sandra Quinto Maurizio Palmisano Francesco Zambonin Pier Giorgio |
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| Institution: | Dipartimento di Chimica, Università degli Studi di Bari,Via Orabona 4, 70126 Bari, Italy. |
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| Abstract: | A fast-response and interference-free amperometric biosensor based on choline oxidase immobilized onto an electropolymerized polypyrrole film for flow injection determination of choline in milk, milk powder, and soy lecithin hydrolysates is described. The sensor displayed an Imax value of 1.9 +/- 0.2 microA and an apparent Michaelis-Menten constant, k'M, equal to 1.75 +/- 0.07 mM. Detection limits of 0.12 microM could be obtained. Because even a slight deterioration of the anti-interference membrane can adversely affect measurement accuracy, a real time monitoring of the biosensor selectivity has been achieved by a dual Pt electrode flow-through cell where the enzyme modified electrode is coupled to an enzyme-free electrode in a parallel configuration. Finally, bracketing technique (alternate injections of sample and standards) allows a two-point calibration to be performed in real-time, correcting for any drift in sensor response. |
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