Heavy-metal analysis of water, environmental and industrial samples typically relies on three methods: AAS (atomic absorption spectrometry), ICP-OES (inductively coupled plasma optical emission spectrometry) and ICP-MS (inductively coupled plasma mass spectrometry). This guide is not a primer on heavy-metal parameters; rather, it is a decision guide comparing the methods across detection limit, throughput, interference and cost for when you need to analyse multiple elements at once.
1. Overview of the Three Methods
- AAS: atomised sample absorbs light at a specific wavelength. Flame (FAAS) and graphite-furnace (GFAAS) variants exist; fundamentally a single-element, sequential measurement
- ICP-OES: a high-temperature plasma excites elements and the emitted spectrum is measured — strong for simultaneous multi-element analysis
- ICP-MS: elements ionised in the plasma are separated and detected by mass-to-charge ratio — capable even of ultra-trace and isotopic analysis
2. Detection-Limit Comparison
Detection limits generally improve in the order ICP-MS (ppt–sub-ppb) > GFAAS > ICP-OES (ppb–ppm) > FAAS. Parameters with very low regulatory limits — trace metals in drinking water such as arsenic, cadmium and lead — call for ICP-MS or GFAAS. For samples at relatively higher concentrations, ICP-OES or FAAS is sufficient.
3. Throughput and Simultaneous Multi-Element Analysis
When there are many target elements and many samples, the simultaneous multi-element analysis of ICP-OES and ICP-MS is overwhelmingly advantageous — a single measurement can quantify dozens of elements at once, giving high throughput. AAS requires changing the light source (lamp) and conditions for each element, so multi-element work takes far longer. For few elements and few samples, AAS remains economical.
4. Interference and Matrix Effects
Each method has characteristic interferences. ICP-OES is prone to spectral (wavelength) overlap, ICP-MS to isobaric and polyatomic-ion interference (mitigated with collision cells), and AAS mainly to chemical and matrix interference. The more complex the sample matrix (high salinity, organics, solids), the more sample preparation and interference-correction strategy drive method choice.
5. Cost and Operating Considerations
Capital and running costs generally follow ICP-MS > ICP-OES > GFAAS > FAAS. ICP-based methods consume argon gas and need skilled operation, and ICP-MS in particular demands operating expertise. Budget and the skill level of available staff are therefore realistic selection variables.
6. Selection Criteria by Sample, Regulation and Budget
- Ultra-trace regulated parameters (drinking-water arsenic, lead, etc.) → ICP-MS or GFAAS
- Many elements / high sample volume at mid concentrations → ICP-OES
- Few elements / limited budget → FAAS or GFAAS
- Isotopic or ultra-trace research → ICP-MS
Ultimately, "what, down to how low a concentration, how many elements and on what budget" determines the method.
Need Help?
Sechang supports the selection of heavy-metal analysers (AAS, ICP-OES, ICP-MS) matched to your analysis purpose, regulatory limits and sample characteristics. If you are unsure which method fits your site conditions, please reach out below.