🔬 Metals in water — ICP-OES
In short
Multi-element analysis of over 30 elements in water using ICP-OES with argon plasma at 6000–10000 K. The test is performed according to PN-EN ISO 11885:2009; Dynamic range: 4–6 orders of magnitude. The procedure comprises 8 steps (about 2 h 22 min–2 h 38 min in total); it is used for: Multi-element drinking water quality control, Monitoring metals in industrial and municipal wastewater, Analysis of groundwater (hydrogeology, geochemistry).
At a glance
- Standard: PN-EN ISO 11885:2009
- Category: Physicochemistry
- Procedure steps: 8
- Total time of stages: 2 h 22 min–2 h 38 min
- Number of determined elements: > 30 simultaneously
- Detection limits: 1–50 µg/L (depending on element)
- Dynamic range: 4–6 orders of magnitude
Overview
ICP-OES (Inductively Coupled Plasma – Optical Emission Spectrometry) is an advanced spectrometric technique enabling simultaneous determination of over 30 elements in a single measurement. Standard PN-EN ISO 11885:2009 specifies the method for determining among others: Al, As, Ba, Be, Bi, B, Ca, Cd, Co, Cr, Cu, Fe, Ga, In, K, Li, Mg, Mn, Mo, Na, Ni, P, Pb, S, Se, Si, Ag, Sr, Sn, Ti, V, W, Zn, Zr in drinking water, surface water, groundwater, and wastewater.
ICP-OES replaces or complements AAS where multi-element analysis, higher sensitivity, or greater throughput is required. Simultaneous determination of many elements in one measurement cycle drastically shortens analysis time and reduces sample consumption.
This technique is widely used in environmental laboratories, water treatment plants, chemical and pharmaceutical industries. Investment cost is higher than AAS, but cost per element is lower when many parameters are analyzed.
Method principle
The sample in solution form is pumped to a nebulizer where it is converted to an aerosol (mist), then introduced into a quartz torch. A radio frequency (RF) generator (27 or 40 MHz) creates an alternating electromagnetic field in an induction coil that ionizes argon creating plasma at 6000–10000 K.
At such high temperature, the sample undergoes evaporation, atomization, and excitation. Excited atoms and ions emit electromagnetic radiation at wavelengths characteristic of individual elements. An optical detector (CCD or PMT) measures emission intensity, which is proportional to element concentration in the sample.
ICP-OES can operate in radial (side-on plasma observation) or axial (end-on) configuration — axial configuration provides higher sensitivity, while radial provides fewer matrix effects.
Applications
- Multi-element drinking water quality control
- Monitoring metals in industrial and municipal wastewater
- Analysis of groundwater (hydrogeology, geochemistry)
- Control of water treatment processes (Al, Fe coagulation)
- Monitoring of surface waters (Water Framework Directive)
- Analysis of mine waters and landfill leachate
Key parameters
| Parameter | Value |
|---|---|
| Number of determined elements | > 30 simultaneously |
| Detection limits | 1–50 µg/L (depending on element) |
| Dynamic range | 4–6 orders of magnitude |
| Throughput | 20–60 samples/h (multi-element) |
| Repeatability | RSD < 1–3% |
| Argon consumption | 10–20 L/min (cost ~30 000–50 000 PLN/year) |
Standard
- Standard number
- PN-EN ISO 11885:2009
- Title (PL)
- Jakość wody — Oznaczanie wybranych pierwiastków metodą optycznej spektrometrii emisyjnej z plazmą indukcyjnie sprzężoną (ICP-OES)
- Title (EN)
- Water quality — Determination of selected elements by inductively coupled plasma optical emission spectrometry (ICP-OES)
Step-by-step procedure
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Sampling and preservation
Collect sample in PE/PP container. Acidify with HNO₃ to pH < 2 (1 mL concentrated HNO₃ per 100 mL). Transport cold, analysis within 14 days.
-
Sample digestion
For total forms: microwave digestion (HNO₃ or HNO₃+HCl). Program: ramp to 180°C in 15 min, hold 15 min. For dissolved forms: filtration 0.45 µm + acidification.
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Preparation of calibration standards
Prepare min. 5 calibration points from certified standard solutions. Acid matrix identical to samples. Add internal standard (Y or Sc).
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ICP-OES startup
Turn on chiller, plasma ignition, stabilization 15–30 min. Check Mn 257.610 nm line intensity (plasma performance test). Optimization of observation position.
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Instrument calibration
Measure calibration standards and blank. Check correlation coefficients (R² > 0.999 for each line). Verify detection limits.
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Sample measurement
Measure samples with automatic rinsing between measurements (30 s acid rinse, 30 s water). Control standard every 10 samples. Duplicate every 20 samples.
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Results verification
Check recovery from reference material (90–110%). Check instrument drift (control standard ±10% of nominal value). Background and spectral interference correction.
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Instrument shutdown
Aspirate deionized water for 5 min. Turn off plasma. Turn off gases after 10 min cooling. Turn off chiller.
Required equipment and apparatus
| Equipment | Example | Indicative price |
|---|---|---|
| ICP-OES spectrometer | Thermo iCAP PRO, Agilent 5800/5900, PerkinElmer Avio 500, Shimadzu ICPE-9820 | 200 000–600 000 PLN |
| Sample introduction system (nebulizer + chamber) | Meinhard pneumatic nebulizer, cyclonic chamber | included with spectrometer |
| Autosampler | Thermo ASX-560, Agilent SPS 4 | 30 000–80 000 PLN |
| Argon cylinder (5.0) | Argon purity 99.999%, 50 L cylinder | 300–500 PLN/cylinder |
| Cooling system | Recirculating chiller (required for RF coil cooling) | 10 000–25 000 PLN |
| Microwave digestion system | Milestone Ethos UP, CEM MARS 6, Anton Paar Multiwave | 100 000–250 000 PLN |
Reagents, media and consumables
| Reagent | CAS | Details |
|---|---|---|
| Concentrated nitric acid (HNO₃) | 7697-37-2 | Suprapur/Ultrapur purity (Merck), for digestion and acidification of samples |
| Hydrochloric acid (HCl) | 7647-01-0 | Suprapur purity, for digestion of samples containing Ag, Sn |
| Multi-element standard solutions | — | Certified CRM (e.g., Merck Certipur, Inorganic Ventures), traceability to NIST |
| Internal standard solution | — | Yttrium (Y) or scandium (Sc) 1–5 mg/L as internal standard for matrix correction |
| Argon gas 5.0 | 7440-37-1 | Purity 99.999%, consumption ~10–20 L/min. Main operating cost |
| Ultrapure water | — | Type I (18.2 MΩ·cm), Milli-Q system or equivalent |
Health and safety (OHS)
- Concentrated nitric acid — highly corrosive and oxidizing. Work in fume hood, acid-resistant gloves
- Argon plasma — UV radiation, do not look directly. UV protective goggles
- Argon — inert gas but displaces oxygen. Room ventilation, O₂ sensor
- Noise from RF generator — use hearing protection during prolonged work
- Solutions containing toxic metals — collect as hazardous waste
- Plasma temperature > 6000°C — quartz torch hot after measurements, do not touch
Frequently asked questions
Which standard describes this test?
The test is performed according to PN-EN ISO 11885:2009 — “Water quality — Determination of selected elements by inductively coupled plasma optical emission spectrometry (ICP-OES)”.
How does this method work?
The sample in solution form is pumped to a nebulizer where it is converted to an aerosol (mist), then introduced into a quartz torch. A radio frequency (RF) generator (27 or 40 MHz) creates an alternating electromagnetic field in an induction coil that ionizes argon creating plasma at 6000–10000 K.
What is the measuring range and accuracy?
Number of determined elements: > 30 simultaneously; Detection limits: 1–50 µg/L (depending on element); Dynamic range: 4–6 orders of magnitude; Throughput: 20–60 samples/h (multi-element).
How long does the test take?
The times given for the individual stages add up to approximately 2 h 22 min–2 h 38 min. The procedure comprises 8 steps.
What equipment is required?
ICP-OES spectrometer, Sample introduction system (nebulizer + chamber), Autosampler, Argon cylinder (5.0), Cooling system, Microwave digestion system. Indicative cost of the core instrument (ICP-OES spectrometer): 200 000–600 000 PLN.
Where is this test used?
Multi-element drinking water quality control; Monitoring metals in industrial and municipal wastewater; Analysis of groundwater (hydrogeology, geochemistry); Control of water treatment processes (Al, Fe coagulation); Monitoring of surface waters (Water Framework Directive); Analysis of mine waters and landfill leachate.
What safety precautions apply?
Concentrated nitric acid — highly corrosive and oxidizing. Work in fume hood, acid-resistant gloves; Argon plasma — UV radiation, do not look directly. UV protective goggles; Argon — inert gas but displaces oxygen. Room ventilation, O₂ sensor; Noise from RF generator — use hearing protection during prolonged work; Solutions containing toxic metals — collect as hazardous waste; Plasma temperature > 6000°C — quartz torch hot after measurements, do not touch.
Which laboratory can perform this test?
The test is performed by laboratories accredited to ISO/IEC 17025. On LabCoda you can find them by the standard number PN-EN ISO 11885.