title: Development of an amperometric assay for phosphate ions in urine based on a chemically modified screen-printed carbon electrode.
abstract: 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(2)O(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 x 10(-5) to 1.81 x 10(-4)M, and the limit of detection was found to be 4.27 x 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 x 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.
authors: Centre for Research in Analytical Materials and Sensor Science, University of the West of England, Bristol, UK.
authors: L
authors: L
authors: Gilbert
authors: A T A
authors: AT
authors: Jenkins
authors: S
authors: S
authors: Browning
authors: J P
authors: JP
authors: Hart
mesh_terms: D015374:Biosensing Techniques / Q000295:instrumentation*; D002138:Calibration; D002244:Carbon; D002482:Cellulose / Q000031:analogs & derivatives; D003067:Coenzymes / Q000378:metabolism; D003653:Decarboxylation; D004800:Enzymes, Immobilized; D006801:Humans; D006861:Hydrogen Peroxide / Q000032:analysis; D006863:Hydrogen-Ion Concentration; D007211:Indoles; D017736:Ion-Selective Electrodes; D008567:Membranes, Artificial; D008832:Microchemistry / Q000295:instrumentation*; D009942:Organometallic Compounds; D010710:Phosphates / Q000652:urine*; D011771:Pyruvate Oxidase / Q000378:metabolism*; D019289:Pyruvic Acid; D013696:Temperature
chemical_list: D003067:Coenzymes; D004800:Enzymes, Immobilized; D007211:Indoles; D008567:Membranes, Artificial; D009942:Organometallic Compounds; D010710:Phosphates; C063633:cobalt phthalocyanine; C005062:acetylcellulose; D002244:Carbon; D019289:Pyruvic Acid; D002482:Cellulose; D006861:Hydrogen Peroxide; D011771:Pyruvate Oxidase