DETERMINATION OF MERCURY AND SILVER AT A MODIFIED CARBON-PASTE ELECTRODE CONTAINING GLYOXAL BIS(2-HYDROXYANIL)

Modified 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 Nujo l oil. Simple immersing of the GHA-modified CPE into the measuring sol ution led to the chemical deposition of the metal ions onto the electr ode. The cyclic, differential pulse, and stripping voltammetry were us ed to characterize the modified electrodes, which selectively responde d to the mercury(II) and silver(I) ions. The analyses of Hg and Ag wer e carried out separately with the CPE in the acetate buffer and neutra l aqueous solution. The electrode surface was regenerated after each m easurement, 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 Ag-I ion. After seven deposition/measurement/regeneratio n cycles, the peak current of the analyte decreased. The response repr oduced around 5% relative standard deviation using the differential pu lse stripping voltammetry. The detection limits for Hg-II and Ag-I ion s were 1.0 x 10(-9) M and 1.0 x 10(-10) M, respectively, for 40 min of deposition. After pretreatment of silver(I) ion with KCl, we could no t observe any interference by other metal ions in the determination of the Hg-II ion in aqueous solution. Our results obtained in the determ ination of mercury are verified using a certified standard urine refer ence material, SRM's 2670 (trace elements in urine).