Development of an amperometric assay for phosphate ions in urine based on a chemically modified screen-printed carbon electrode

• Published in: Analytical biochemistry Vol. 393; no. 2; pp. 242 - 247
• Main Authors: Gilbert, L., Jenkins, A T.A., Browning, S., Hart, J.P.
• Format: Journal Article
• Language: English
• Published: United States Elsevier Inc 15.10.2009
• Subjects: Amperometry; Biosensing Techniques - instrumentation; Calibration; Carbon; Cellulose - analogs & derivatives; Cobalt phthalocyanine; Coenzymes - metabolism; Decarboxylation; Enzymes, Immobilized; Humans; Hydrogen Peroxide - analysis; Hydrogen-Ion Concentration; Indoles; Ion-Selective Electrodes; Membranes, Artificial; Microchemistry - instrumentation; Organometallic Compounds; Phosphate; Phosphates - urine; Pyruvate Oxidase - metabolism; Pyruvic Acid; Screen-printing; Temperature; Urine; Urine; Amperometry; Cobalt phthalocyanine; Screen-printing; Phosphate
• ISSN: 0003-2697; 1096-0309; 1096-0309
• DOI: 10.1016/j.ab.2009.06.038

An amperometric assay for the determination of inorganic phosphate (Pi) in urine has been developed without the need for sample preparation. A screen-printed carbon electrode modified with the electrocatalyst cobalt phthalocyanine (CoPC–SPCE) and covered with a cellulose acetate membrane (CAM) serves as the sensor. The sensor detects hydrogen peroxide (H 2O 2), which is produced as a result of the oxidative decarboxylation of pyruvate, catalyzed by pyruvate oxidase (PyOd), in the presence of Pi, oxygen, and cofactors. Following optimization of solution conditions, and in the presence of a urine sample, a linear range was found to exist between the rate of current increase and phosphate concentration over the range of 2.27 × 10 −5 to 1.81 × 10 −4 M, and the limit of detection was found to be 4.27 × 10 −6 M. The assay was applied to the determination of phosphate ions in the urine of a normal subject, and the mean concentration in unspiked urine was found to be 3.40 × 10 −5 M with a coefficient of variation of 8.0% ( n = 5). The mean recovery of phosphate added to urine samples was 98.7% with a coefficient of variation of 5.5% ( n = 3). To the authors’ knowledge, this is the first report of an amperometric assay for Pi that incorporates a CoPC–SPCE as the sensing device.