Arsenic speciation in natural waters by cathodic stripping voltammetry

Area of Science:

• Environmental Science
• Analytical Chemistry
• Water Quality Monitoring

Background:

• Arsenic contamination in groundwater poses a significant health risk, particularly the highly toxic As(III) species.
• Existing methods for arsenic determination lack suitability for in-situ speciation analysis at original pH and without sample preparation.

Purpose of the Study:

• To develop and validate a novel method for determining reactive arsenic(III) and total dissolved arsenic in groundwater.
• To enable arsenic speciation analysis at original pH and without prior sample manipulation.

Main Methods:

• Utilized cathodic stripping voltammetry (CSV) with a vibrating gold microwire electrode to detect reactive As(III).
• Employed adsorptive deposition of As(OH)(3)(0) followed by electrochemical reduction for As(III) detection.
• Developed a protocol involving CSV for As(III) at original pH and anodic stripping voltammetry (ASV) after acidification for As(III)+As(V) and total dissolved arsenic determination.

Main Results:

• The method accurately determines reactive As(III) in waters with pH 7-12.
• Achieved an analytical range of 1 nM to 100 microM (0.07-7500 ppb) with a limit of detection of 0.5 nM for As(III).
• Successfully applied the speciation protocol to diverse raw groundwater samples from the UK and West Bengal.

Conclusions:

• The presented CSV and ASV method offers a robust and sensitive approach for arsenic speciation in groundwater.
• This technique facilitates on-site monitoring of toxic arsenic species, improving water safety assessments.
• The method's suitability for various groundwater conditions highlights its potential for widespread application in public health protection.