Cobalt(II) tetrasulfophthalocyanine complex adsorbed on a silica gel surface chemically modified with 3-N-propylpyridinium chloride: Oxalic acid oxidation study

Cobalt(II) tetrasulfophthalocyanine complex was adsorbed on the 3-N-propylp yridinium chloride functionalized silica gel surface bit means of an ion ex change reaction. The specific surface area of the modified silica was S-BET = 320 m(2) g(-1) and the amount of the complex bonded to the substrate sur face was 17 mu mol g(-1). A carbon paste electrode made with electrocatalyt ically oxidized oxalic acid at an anodic potential E-pa = 850 mV in 0.5 M K Cl solution at pH 2. The anodic peak current intensities were linearly corr elated with oxalic acid concentrations between 3.97 and 19.2 x 10(-3) M. Th e electrode shelved a very reproducible response and was chemically very st able under various oxidation-reduction cycles. The electrode was applied in the determination of oxalic acid in a spinach sample.