What Is a Heavy Metal Test? Methods, Detection Limits & Applications
What Are Heavy Metals?
Heavy metals are a group of metallic elements with relatively high atomic mass and density that are toxic or hazardous to human health and environmental organisms at low concentrations. The most regulated heavy metals include lead (Pb), cadmium (Cd), mercury (Hg), arsenic (As), chromium (Cr — particularly hexavalent Cr⁶⁺), antimony (Sb), barium (Ba), and selenium (Se). They accumulate in biological systems (bioaccumulation) and are persistent in the environment.
Heavy metal testing is the analytical determination of the concentration of these elements in materials, products, water, soil, and biological samples — verifying compliance with regulatory limits designed to protect human health and environmental quality.
Why Heavy Metal Testing Is Required
Heavy metals enter products, materials, and the environment from multiple industrial sources: mining and smelting, electroplating and surface treatment, pigments and colorants, stabilisers in PVC, solder alloys, electronic components, and industrial wastewater. Their persistence and bioaccumulation make them subject to strict regulatory controls:
- RoHS Directive (EU): Restricts Pb, Hg, Cd, Cr⁶⁺, PBB, PBDE in electrical and electronic equipment to maximum concentrations of 0.1% (1000 ppm) for most substances and 0.01% (100 ppm) for cadmium
- REACH Regulation (EU): SVHC restrictions on lead compounds, mercury compounds, and hexavalent chromium in articles above 0.1% concentration
- EPA Drinking Water MCLs: Lead <15 µg/L, Arsenic <10 µg/L, Mercury <2 µg/L, Cadmium <5 µg/L
- CPSC Regulations (USA): Lead in children’s products <100 ppm; lead in paint <90 ppm (ASTM F963)
- California Proposition 65: Warning requirements for products exposing consumers to listed heavy metals above safe harbour levels
Heavy Metal Test Methods
X-Ray Fluorescence Spectrometry (XRF) — IEC 62321-1, ASTM F2617
XRF is the primary screening method for heavy metals in solid materials and products for RoHS compliance verification. A polychromatic X-ray beam irradiates the specimen surface; the characteristic fluorescent X-rays emitted by each element are detected and quantified. XRF provides:
- Non-destructive, rapid screening (30–60 seconds per analysis)
- Simultaneous multi-element analysis
- Detection limits of ~10–100 ppm for most heavy metals
- No sample preparation for solid specimens
Handheld XRF analysers enable in-the-field or production-line screening of electronic components, toys, and materials for heavy metal content.
ICP-OES and ICP-MS — EPA Methods 200.7 and 200.8
For confirmation analysis, regulatory reporting, and trace-level quantification, ICP-OES and ICP-MS are used after dissolution of the solid specimen in acid digestion. ICP-MS achieves detection limits of 0.001–0.1 µg/L (ppt) for most heavy metals — far below regulatory limits — providing definitive compliance determination.
Hexavalent Chromium (Cr⁶⁺) Specific Analysis — IEC 62321-7-2, ASTM D1687
Cr⁶⁺ must be distinguished from total chromium because it is a potent carcinogen while Cr³⁺ is relatively benign. Methods include:
- Colorimetric method (diphenylcarbazide, DPC): Cr⁶⁺ reacts with DPC to form a violet-red colour, quantified by UV-Vis spectrophotometry
- Ion chromatography (IC) with UV/post-column DPC: For water samples — EPA Method 218.6, ISO 10304-3
Mercury Specific Analysis — ASTM D3223, EPA Method 245.1
Mercury requires specialised analytical methods due to its volatility and toxicity:
- Cold vapour atomic absorption (CVAA): Most widely used method for mercury in water and solutions
- Direct mercury analyser (ASTM D6722): Combustion of solid or liquid samples, amalgam trapping, and atomic absorption — enabling mercury analysis without acid digestion
Industrial Applications
In electronics and electrical equipment manufacturing, heavy metal testing to IEC 62321 is mandatory for RoHS compliance before CE marking and market release in the EU and many other global markets. Toy manufacturers test paints, surface coatings, and plastics for heavy metals per ASTM F963 (US) and EN 71-3 (EU) to verify consumer safety. Water utilities test treated drinking water and distribution system compliance against EPA MCLs for lead, arsenic, cadmium, and mercury.
Why Choose Infinita Lab for Heavy Metal Testing?
Infinita Lab provides comprehensive heavy metal analysis — XRF screening, ICP-OES/ICP-MS confirmation, Cr⁶⁺ speciation, and mercury analysis — per IEC 62321, EPA, and ASTM methods through our nationwide accredited analytical chemistry laboratory network.
Looking for a trusted partner to achieve your research goals? Schedule a meeting with us, send us a request, or call us at (888) 878-3090 to learn more about our services and how we can support you.
Frequently Asked Questions (FAQs)
What are the RoHS restricted heavy metals and their maximum concentration limits? RoHS Directive 2011/65/EU restricts: Lead (Pb) ≤1000 ppm (0.1%), Mercury (Hg) ≤1000 ppm, Hexavalent chromium (Cr⁶⁺) ≤1000 ppm, Cadmium (Cd) ≤100 ppm (0.01%) in homogeneous materials in electrical and electronic equipment.
Why is XRF used for RoHS screening rather than full ICP analysis of all samples? XRF provides rapid, non-destructive multi-element screening of all elements simultaneously in minutes — cost-effectively identifying samples likely to be non-compliant for follow-up ICP confirmation. ICP analysis requires chemical dissolution and is more time-consuming and expensive. XRF screens hundreds of samples per day; ICP provides definitive quantification for flagged specimens.
What is the difference between total chromium and hexavalent chromium (Cr⁶⁺) testing? Total chromium includes all oxidation states (Cr³⁺, Cr⁶⁺, Cr²⁺, Cr⁰). XRF and ICP-OES measure total chromium. Cr⁶⁺ — the toxic, carcinogenic form used in electroplating and surface treatment — must be specifically detected by speciation methods (DPC colorimetry, IC) because Cr³⁺ at the same total concentration poses negligible health risk.
What is the CPSC lead limit for children's products and how is it tested? The Consumer Product Safety Improvement Act (CPSIA) limits lead content to 100 ppm in children's products and 90 ppm in paints/surface coatings. Testing is typically performed by XRF screening (ASTM F2617) followed by ICP-OES confirmation digestion (ASTM F2853) when XRF results exceed the limit or are close to the decision threshold.
Can heavy metal testing be performed on coatings and paints without removing them from the substrate? XRF can screen paint and coating films on substrates non-destructively for heavy metals — providing data on the combined coating+substrate system. For pure coating analysis, the paint is stripped or scraped from the substrate, digested, and analysed by ICP. For water-based paints in containers, direct XRF of paint discs or ICP of acid-digested paint samples provides compliance data.
