The Amperometric Response Of Ag/Zsm-5/CPE

Fig. 7A displays the amperometric response of Ag/ZSM-5/CPE with successive injection of OA into a stirred solution of 0.1 M NaHPO4 pH= 2 recorded at the potential of 0.73 V vs. Ag|AgCl in the concentration ranges from 16 μM to 4.0 mM. It can be seen that the aerometric current increases clearly after each injection of OA. Fabricated sensor displays the rapid response towards change in the concentration of OA which reaches a steady state within 2 s by applying the potential of 0.73 V to Ag/ZSM-5/CPE. A calibration plot of the amperometric current response versus oxalic acid concentration is displayed in Fig. 7B.

Fig. 7

Results show that Ag/ZSM-5/CPE electrode can detect OA in linear ranges of 16 μM–0.18 mM and 0.18 mM–4.0 mM with a detection
Ag/ZSM-5/CPE indicates an immediate amperometric response toward the addition of 0.2 mΜ OA, whereas no remarkable effect was observed for the 50-fold excess concentration of possible interferrants such as ethylene glycol (E.G) (CH2OH-CH2OH), glyoxylic acid (GA) (CHO-COOH), dimethyl oxalate (DO) (CH3OOC-COOCH3) and glycolic acid (CH2OH-COOH) (Fig. 8A). However, a considerable response was observed after further addition of 0.2 mM OA into the solution containing of interferences. These results show that this sensor has high selectivity toward OA. Also, another interfererants such as ascorbic acid, tyrosine and uric acid may be interferences for the detection of OA at the Ag/ZSM-5/CPE. In order to investigate the influence of these the interferences, 0.2 mM of each species was added in solution containing of 0.1 M NaHPO4 pH= 2 buffer solution in presence of 0.2 mM of OA, and the amperometric response of sensor is displayed in Fig. 8B. It can be observed in Fig. 8B that these species had no significant effect on the amperometric response of OA. The obtained results confirm that mentioned compounds do not display interference