A 9.0 mL aliquot of synthetic sea water (ASTM D665) contaminated
with a standard solution containing lead, cadmium and zinc
(5.0 lg L1
), was added to the electrochemical cell that contained
1.0 mL of BR buffer and 30 lL of CQ 1.2 mmol L1 adjusting to
the 5.3 pH with NaOH solution. The analysis of these metal ions
was carried out using the standard addition method. The values
obtained were 4.8 ± 0.3; 5.0 ± 0.1; 4.9 ± 0.2 lg L1
; (RE 4.0%,
0.0% and 2.0%) respectively for lead, cadmium and zinc. The usefulness
of the present method was also evaluated by determining
these analytes in certified reference water TMDA-61. Fig. 6 shows
differential pulse voltammograms and calibration plot obtained
when 0.5 mL of TMDA-61 sample was added to 8.5 mL of deionized
water, 1.0 mL of BR buffer pH 5.3 (0.3 mol L1
) and 30 lL of
1.2 mmol L1 CQ. The values obtained for lead, cadmium and zinc
were 65.6 ± 1.2; 59.5 ± 0.6; 69.9 ± 0.9 lg L1
; (RE 6.8%, 2.6% and
2.0%). These values are satisfactory because this reference lake
Ontario water contains about 28 metal ions with concentrations
between 3.2 and 113 lg L1
.
3.4. Rea