Detection of heavy metals with differential pulse voltammetry

Importance of the Topic

Differential pulse voltammetry (DPV) is a highly sensitive electroanalytical technique for detecting trace levels of heavy metal ions in aqueous environments. Because heavy metals such as lead (Pb) and cadmium (Cd) pose serious environmental and health risks, reliable quantification methods are essential for water quality monitoring, regulatory compliance, and research applications.

Goals and Overview of the Study

This application note presents a voltammetric approach to quantify Pb and Cd ions in water samples using DPV. The study demonstrates how Metrohm’s INTELLO and NOVA software platforms, combined with standard addition calibration, enable accurate determination of heavy metal concentrations down to the low microgram-per-liter range.

Methodology and Instrumentation

DPV measurements were performed by superimposing a constant-height pulse onto each step of a staircase linear sweep. Samples were preconditioned by forming a fresh mercury drop on a hanging dropping mercury electrode (HDME). Under nitrogen purging and stirring, Pb2+ and Cd2+ ions were reduced onto the mercury surface at –0.9 V. After accumulation, stirring was halted and the potential was swept positively from –0.9 V to –0.2 V. Two successive standard additions of known Pb and Cd concentrations allowed calibration by plotting peak current versus added concentration.

Used Instrumentation

• Autolab PGSTAT302N potentiostat/galvanostat
• Metrohm 663 VA measuring stand
• Multi-Mode Electrode pro (HDME) hanging dropping mercury electrode
• Double junction Ag/AgCl reference electrode
• Acetate buffer electrolyte (1 mol/L ammonium acetate + 1 mol/L acetic acid)

Main Results and Discussion

DPV oxidation peaks for Cd and Pb appeared at –0.58 V and –0.40 V, respectively. Peak heights increased linearly with each standard addition. Regression of peak current against added concentration yielded x-axis intercepts corresponding to sample concentrations of 12.04 µg/L for Cd and 12.41 µg/L for Pb. These results demonstrate the method’s precision and the ability to correct for matrix effects via standard addition.

Benefits and Practical Applications

• High sensitivity and selectivity for trace heavy metals
• Effective separation of closely spaced oxidation peaks
• Compatibility with existing electrochemical platforms (INTELLO and NOVA)
• Standard addition calibration minimizes matrix interference

Future Trends and Opportunities

Advancements include integration of VIONIC powered by INTELLO for higher voltage and current capacity, miniaturized and field-deployable DPV systems, and automated on-site monitoring. Improved software algorithms will further enhance data processing and result accuracy.

Conclusion

DPV coupled with standard addition provides a robust, sensitive, and accurate approach for quantifying Pb and Cd in water samples. Metrohm’s instrumentation and software streamline the workflow, making this method well suited for environmental analysis, quality control, and research applications.

References

Metrohm Application Note AN-SENS-002: Detection of Heavy Metals with Differential Pulse Voltammetry