Rapid and convenient determination of oxalic acid employing a novel oxalate biosensor based on oxalate oxidase and SIRE technology.

A new method for rapid determination of oxalic acid was developed using oxalate oxidase and a biosensor based on SIRE (sensors based on injection of the recognition element) technology. The method was selective, simple, fast, and cheap compared with other present detection systems for oxalate. The total analysis time for each assay was 2-9 min. A linear range was observed between 0 and 5 mM when the reaction conditions were 30 degrees C and 60 s. The linear range and upper limit for concentration determination could be increased to 25 mM by shortening the reaction time. The lower limit of detection in standard solutions, 20 microM, could be achieved by means of modification of the reaction conditions, namely increasing the temperature and the reaction time. The biosensor method was compared with a conventional commercially available colorimetric method with respect to the determination of oxalic acid in urine samples. The urine oxalic acid concentrations determined with the biosensor method correlated well (R=0.952) with the colorimetric method.