Development of acid phosphate inhibition-based amperometric biosensor for determination of inorganic phosphate

The present study describes construction of amperometric biosensor for determination of inorganic phosphate (IP) using single enzyme acid phosphatase (ACP). A blend of biopolymers agarose and guar gum was used to immobilize ACP and estimation of inorganic phosphate was carried out electrochemically using substrate L-ascorbic acid-2-phosphate. Enzyme catalyzes substrate hydrolysis and ascorbic acid is formed as a product which shows oxidation peak at +0.08 V. This peak intensity decreases when enzyme electrode is dipped in inorganic phosphate solution prior to monitoring substrate hydrolysis. The response is linear in the range of 1 × 10^-6 M to 4 × 10^-5 M IP with a detection limit of 5 × 10^-7 M. The enzyme sensor was stable over a period of three months with a marginal loss in enzyme activity when stored at 4° C under dry conditions. This single enzyme approach tries to overcome the drawbacks of multi-enzyme system for inorganic phosphate determination yet maintaining sensitivity and selectivity of enzymatic methods. Possible influence of other species coexisting with inorganic phosphate in water samples was investigated. The performance of this single enzyme based biosensor was in good agreement with earlier reports on biosensors for inorganic phosphate determination using multi-enzyme approach.