Arsenic measurement using anodic stripping voltammetry

Abstract

Measurement of arsenic in an aqueous solution is provided. The pH of the aqueous solution is adjusted to a pH of about 7.0 or higher. The pH adjusted aqueous solution is then analyzed using anodic stripping voltammetry to obtain an indication of a quantity of arsenic in the solution. In one aspect, the pH is adjusted using a phosphate buffer.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagrammatic view of an arsenic measurement system employing anodic stripping voltammetry in accordance with an embodiment of the present invention.

FIG. 2 is a flow diagram of a method of measuring arsenic in an aqueous sample in accordance with an embodiment of the present invention.

FIG. 3 is a chart illustrating various examples of anodic stripping voltammetry using square wave voltammetry of arsenic (III) in a pH 7 phosphate buffer with a gold working electrode.

Claims

1. A system for quantifying the presence of arsenic in an aqueous sample, the system comprising: a working electrode configured to contact the sample;a second electrode configured to contact the sample;a pH-adjusting material disposed within the aqueous sample, the pH adjusting material configured to adjust the pH to at least about 7.0; andan analyzer coupled to the working electrode and the second electrode, the analyzer being configured to perform anodic stripping voltammetry on the pH adjusted sample to determine an amount of arsenic in the sample.

2. The system of claim 1, wherein the pH-adjusting material is a buffer.

3. The system of claim 2, wherein the buffer is a phosphate buffer.

4. The system of claim 1, and further comprising an additional additive to the sample, the additive being configured to react with at least one interfering metal.

5. The system of claim 4, wherein the additive is a chelating ligand.

6. The system of claim 5, wherein the chelating ligand is ethylenediaminetetraacetic acid.

7. The system of claim 1, wherein the working electrode is constructed from a material selected from the group consisting of gold, graphite, glassy carbon, and diamond thin film.

8. A method for measuring a quantity of arsenic in an aqueous sample, the method comprising: adjusting the pH of the aqueous sample to be at least 7.0;generating a negative potential on a working electrode for a period of time; andreversing the potential of the working electrode and measuring a current related to the presence of arsenic in the sample.

9. The method of claim 8, wherein adjusting the pH of the aqueous sample includes adding a buffer to the sample.

10. The method of claim 9, wherein the buffer is a phosphate buffer.

11. The method of claim 8, and further comprising adding at least one chelating ligand to the aqueous sample.

12. The method of claim 11, wherein the chelating ligand is ethylenediaminetetraacetic acid.