Construction and Characterization of a Beet Stem Based Biosensor for Oxalate

This report describes the construction and characterization of an oxalate-sensing electrode. The electrode is based on the incorporation of ground beet stem into the graphite paste of a graphite paste electrode. The hydrogen peroxide generated by enzymatic degradation of oxalate is monitored at a working voltage of 0.900 V vs SCE. All measurements were conducted in a succinic acid/EDTA buffer at pH 4.00. Under these conditions, the electrodes exhibit reproducible responses to oxalate. The lower limit of oxalate detection was less than 1.03 × 10−4 M. The time to achieve a steady state response after exposure to a step change in oxalate concentration in solution is less than one minute. The magnitude of response to oxalate over the oxalate concentrations studied varies among several electrode tested as does the degree of linearity of response. An electrode studied still exhibited analytically useful responses to oxalate on the 15th day of its use. The beet stem-based electrodes display little respo...