Determination of mercury and silver at a modified carbon paste electrode containing glyoxal bis(2‐hydroxyanil)

Abstract

AbstractModified carbon paste electrodes(CPEs) for the analysis of mercury and silver have been constructed by incorporating a Schiff base, glyoxal bis(2‐hydroxyanil) (GHA) into the graphite powder and mixing with Nujol oil. Simple immersing of the GHA‐modified CPE into the measuring solution led to the chemical deposition of the metal ions onto the electrode. The cyclic, differential pulse, and stripping voltammetry were used to characterize the modified electrodes, which selectively responded to the mercury(II) and silver(I) ions. The analyses of Hg and Ag were carried out separately with the CPE in the acetate buffer and neutral aqueous solution. The electrode surface was regenerated after each measurement, by cycling the potential from more positive than that for the stripping of the reduced Hg to the more negative than that for the reduction of AgI ion. After seven deposition/measurement/regeneration cycles, the peak current of the analyte decreased. The response reproduced around 5% relative standard deviation using the differential pulse stripping voltammetry. The detection limits for HgII and AgI ions were 1.0 × 10−9 M and 1.0 × 10−10 M, respectively, for 40 min of deposition. After pretreatment of silver(I) ion with KCl, we could not observe any interference by other metal ions in the determination of the HgII ion in aqueous solution. Our results obtained in the determination of mercury are verified using a certified standard urine reference material, SRM's 2670 (trace elements in urine).