Development of an amperometric biosensor for β-N-oxalyl-L-α,β-diaminopropionic acid (β-ODAP)

An amperometric method for the determination of the neurotoxic amino acid beta-N-oxalyl-L-alpha,beta-diaminopropionic acid (P-ODAP) using a screen printed carbon electrode (SPCE) is reported. The electrode material was bulk-modified with manganese dioxide and used as a detector in flow injection analysis (FIA). The enzyme glutamate oxidase (GlOx) was immobilized in a Nafion-film on the electrode surface. The performance of the biosensor was optimized using glutamate as an analyte. Optimum parameters were found as: operational potential 440 mV (vs. Ag/ AgCl), flow rate 0.2 mL min(-1), and carrier composition 0.1 mol L-1 phosphate buffer (pH 7.75). The same conditions were used for the determination of beta-ODAP The signal was linear within the concentration range 53 - 855 mumol L-(1) glutamate and 195-1950 mumol L-1 beta-ODAP. Detection limits (as 3sigma value) for both analytes were 9.12 and 111.0 mumol L-1, respectively, with corresponding relative standard deviations of 3.3 and 4.5%. The biosensor retained more than 73% of its activity after 40 days of on-line use.