Heavy metals like lead (Pb), mercury (Hg), cadmium (Cd), and arsenic (As) can be toxic even at very low concentrations. Detecting them in environmental samples (water, soil, air, plants) requires sensitive and accurate techniques.
Common Methods for Detecting Heavy Metals
1. Atomic Absorption Spectroscopy (AAS)
- Measures absorption of specific wavelengths of light by metal atoms.
- Can detect metals in water, soil, or biological samples.
- Graphite Furnace AAS (GFAAS) is used for very low concentrations.
2. Inductively Coupled Plasma Techniques
- ICP-OES (Optical Emission Spectroscopy): Detects multiple metals simultaneously.
- ICP-MS (Mass Spectrometry): Extremely sensitive; can detect trace and ultra-trace levels.
3. X-ray Fluorescence (XRF)
- Non-destructive technique that detects metals in soil, sediments, or solids.
- Measures characteristic X-rays emitted by elements when irradiated.
4. Electrochemical Methods
- Anodic stripping voltammetry (ASV) measures metal ions in water.
- Sensitive and can detect trace levels of heavy metals.
5. Colorimetric and Spectrophotometric Methods
- Use chemical reagents that form colored complexes with metals.
- Example: Dithizone method for lead.
- Simpler but less sensitive than AAS or ICP.
6. Chromatography Coupled with Detection
- HPLC or GC coupled with AAS or MS can separate metal-containing compounds before detection.
- Useful for organometallic compounds like methylmercury.
In short:
Heavy metals in environmental samples are detected using AAS, ICP-OES/MS, XRF, electrochemical methods, and colorimetric techniques, depending on the sample type, concentration, and required sensitivity.