Differential pulse anodic stripping voltammetric determination of heavy metals (Zn, Cd, Pb and Cu) in water

Date

4-1997

Degree

Bachelor of Science in Chemistry

College

College of Arts and Sciences (CAS)

Adviser/Committee Chair

Maxima E. Flavier

Co-adviser

Jose H. Santos

Abstract

ABSTRACT

MORAGA, WALTER C. University of the Philippines Los Banos, April 1997. Differential pulse anodic stripping voltammetric determination of heavy metals (Zn, Cd, Pb, and Cu) in water.

Adviser: Dr. Maxima E. Flavier

co-adviser: Dr. Jose H. Santos

Differential pulse anodic stripping voltammetry (DPASV) is one of the most sensitive electroanalytical technique. It is capable of detecting up to the nanogram-per-liter range, and can determine four to six elements simultaneously. The technique is applied in the determination of zinc, cadmium, lead, and copper at trace levels in samples of river, sea, and tap water without pretreatment. Deposition time and scan rate were parameters optimized. The effect of supporting electrolyte was studied using potassium chloride, nitric acid and acetate buffer at pH 4.6 as the supporting electrolytes. It was found out that a two minute deposition time and scan rate of 5 mVs-1 satisfactorily gave stripping peaks linear within the working concentration range of 2-200 ppb. Characteristic half-wave potentials were observed at -1.01 to -1.08 V for zinc, -0.60 to -0.66 V for cadmium, -0.41 to -0.46 V for lead and at 0.00 to -0.13 V for copper. Detection limit of 0.60, 0.02, 0.15, and 0.45 ppb were established for zinc, cadmium, lead and copper, respectively based on a 2:1 signal to noise ratio. River water was analyzed to contain 0.10 ± 0.00 ppb cadmium, 4.59 ± 1.04 ppb lead and 5.44 ± 1.29 ppb copper using 0.1 M KCl. In nitric acid, 0.17 ± 0.00, 6.10 ± 0.40 and 15.0 ± 1.30 parts per billion cadmium, lead and copper were detected. Zinc in river water was determined only with acetate buffer and its concentration is 114.3 ± 1.37 ppb. Cadmium level is at 1.10 ± 0.05; lead at 5.60 ± 0.32; and copper at 5.30 ± 0.52 parts per billion. Sea water was reported to have 1.12 ± 0.16 ppb cadmium, 4.59 ± 1.04 ppb lead, and 5.44 ± 0.68 ppb copper using KCl. In acetate buffer, 36.7 ± 1.43 ppb zinc, 4.40 ± 0.12 ppb lead and 7.20 ± 0.18 ppb copper were detected. Cadmium was not detected in sea water. In this study, the use of nitric acid as the supporting electrolyte was found to be not applicable. Tap water was detected to contain 83.58 ± 8.99 ppb zinc, 0.07 ± 0.00 ppb cadmium, 0.75 ± 0.29 ppb lead and 5.82 ± 1.29 copper • Results from nitric acid show 89.18 ± 7.78 ppb zinc, 0.04 ± 0.00 ppb cadmium, 1.50 ± 0.10 ppb lead and 3.80 ± 0.52 ppb copper contents. Using acetate, greatest concentrations were reported. It was found that 112.8 ± 10.48 µg zinc, 1.10 ± 0.05 µg cadmium, 4.50 ± 0.63 µg lead and 16.0 ± 0.52 µg copper were contained per liter of tap water. Interference associated mainly with zinc and its relatively large concentration did not permit the simultaneous determination of the four metals in some sample. The use of a buffered system, however, minimized if not eliminated, the interference allying simultaneous determination of the heavy metals in sea and river water.

Language

English

Location

UPLB Main Library Special Collections Section (USCS)

Call Number

LG 993.5 1997 C4 M67

Document Type

Thesis

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