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Abstract
The features of a biosensor based on a platinum electrode modified with a poly(phenol) film coupled with two enzymes, alkaline phosphatase(AP) and glucose oxidase(GOD), were studied. The modification of the surface of the working electrode decreases interference from ascorbic acid, uric acid and some oxidizable organic materials (e.g. glycine), and decreases the noise of the current. The concentration of substrate, the activity ratio of the two enzymes, the applied potential, and the assembling of biosensor are important for the determination of low levels of phosphate.
The two enzymes have been immobilized on an Immobilon(R) membrane. The linearity range appears in two sections with different sensitivity: one from 8-110 μmol I−1 and another one from 0.1-1.0 mmol I−1, with 1.2 μA/mmol/cm2 and 0.4 μA/mmol/cm2, respectively. Except for some heavy metal ions, ascorbic acid and some oxidizable organic materials, common anions and cations don't interfere with the determination of phosphate.
The biosensor has been used to determine phosphate in some synthetic and real samples with a detection limit of 4 μmol I−1 of phosphate. The results were compared with a standard spectrophotometric method. The accuracy and recovery of phosphate with the biosensor procedure are ±2% and 96 to 103%, respectively.
∗Visiting scientist on leave from Institute of Soil Science, Academia Sinica 210008, Nanjing, China.
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∗Visiting scientist on leave from Institute of Soil Science, Academia Sinica 210008, Nanjing, China.