Electrochemical heavy metal analysis detector

Anodic stripping voltammetry (ASV) is a highly sensitive electrochemical analysis technique suitable for the detection of trace heavy metals such as lead, cadmium, and copper. The following is a key point analysis:

1. Basic principles

ASV is divided into two stages:

• Electrochemical enrichmentUnder negative potential, target metal ions (such as Pb ² ⁺, Cd ² ⁺, Cu ² ⁺) are reduced to metallic states and deposited on the surface of working electrodes (such as glassy carbon electrodes or mercury film electrodes) to achieve pre concentration.
• Dissolution analysisReverse application of forward potential scanning causes the deposited metal to be oxidized back into ions, resulting in characteristic dissolution current peaks. Qualitative analysis through peak potential, quantitative analysis through peak current or area.

2. Testing process

• Sample pretreatmentAcidification, filtration, or digestion (complex matrices require removal of organic/particulate matter).
• Support electrolyte selectionAcetic acid buffer or potassium nitrate are commonly used to adjust pH and enhance conductivity.
• Deoxygenation treatmentRemove dissolved oxygen by passing nitrogen/argon gas to avoid interference.
• Enrichment parameter optimizationAdjust the sedimentation potential (e.g. -1.2 V vs. Ag/AgCl), time (60-300 seconds), and stirring speed to enhance sensitivity.
• Dissolution scanning modeDifferential pulse voltammetry (DPV) can improve resolution and distinguish adjacent peaks (such as Cd ² ⁺, Pb ² ⁺, Cu ² ⁺ peaks with potential differences of about 0.1-0.3 V).

3. Quantitative methods

• Standard Curve MethodEstablish peak current concentration relationship using a known concentration standard solution.
• standard addition methodSuitable for complex substrates to counteract background interference.

4. Metal leaching characteristics

• Typical peak potential (vs. Ag/AgCl)：
  • Cadmium (Cd ² ⁺): Approximately -0.8 V
  • Lead (Pb ² ⁺): approximately -0.5 V
  • Copper (Cu ² ⁺): approximately -0.1 V
• sequenceThe dissolution peak appears in sequence from negative to positive potential (Cd → Pb → Cu).

5. Key influencing factors

• electrode materialMercury film electrodes have high sensitivity but are toxic, while glassy carbon electrodes are more environmentally friendly but require surface modification (such as bismuth film).
• Interference controlChelating agents (such as EDTA) can mask coexisting ions or selectively enrich target metals by adjusting pH.
• pollution prevention and controlUltra pure reagents and acid washed containers to avoid environmental cross contamination (especially for ppb level detection).

6. Applications and advantages

• sensitivityThe detection limit is as low as μ g/L or even ng/L.
• Simultaneous detection of multiple elementsA single scan can analyze multiple metals (if peak potential separation is good).
• Applicable scenariosDetection of trace heavy metals in environmental water samples, food, and biological fluids.

7. Precautions

• Electrode maintenanceRegularly polish the glassy carbon electrode and avoid drying the mercury film electrode.
• parameter validationOptimize sedimentation time, scanning rate, etc. for different samples to avoid overload or signal saturation.
• Regulatory complianceFollow laboratory safety regulations, especially when dealing with mercury or strong acid.

Through the above steps, ASV can efficiently and accurately quantify heavy metals such as lead, cadmium, copper, etc., which is suitable for environmental monitoring and food safety fields. In practical applications, it is necessary to optimize methods based on sample characteristics to ensure data reliability.