Inductively Coupled Plasma Spectrometry
Also known as: ICP-OES, ICP-AES, ICP-MS, plasma emission spectroscopy
Inductively coupled plasma spectrometry is a powerful multi-element analytical technique that ionizes a sample in a high-temperature plasma and measures the emitted light (ICP-OES) or ion masses (ICP-MS) to determine elemental concentrations. Developed in the 1960s by Stanley Greenfield, ICP techniques have become the standard for trace element analysis across environmental, geological, biological, and industrial fields. The method combines exceptional sensitivity, wide dynamic range, and the ability to analyze dozens of elements simultaneously.
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When to use it
ICP spectrometry excels when multiple elements need rapid, simultaneous analysis with high sensitivity and low detection limits. Use ICP-OES for analysis of 10–70 elements at trace to major levels in complex matrices; use ICP-MS when ultra-trace detection (<ppb levels) or isotope analysis is required. ICP-MS offers superior detection limits and interference resolution; ICP-OES offers simplicity, lower cost, and better tolerance to high salt concentrations.
Strengths & limitations
- Simultaneous determination of 20–70+ elements in a single run
- Excellent detection limits (ppb to ppm levels for most elements)
- Wide linear dynamic range, often 4–6 orders of magnitude
- Minimal spectral interference compared to flame methods due to high-temperature environment
- Fully automated analysis possible with modern instrumentation
- ICP-MS capability for isotope ratio determination and isotope dilution analysis
- Requires high-purity reagents and careful contamination control during sample preparation
- Spectral overlaps occur (especially in ICP-OES) when elements have similar emission lines
- High matrix salt content can suppress ionization (matrix suppression) or cause clogging of nebulizer or sampling interface
- Instrument cost and maintenance are significantly higher than single-element techniques
- Requires certified reference materials and frequent calibration for accurate quantification
Frequently asked
What is the difference between ICP-OES and ICP-MS?
ICP-OES (optical emission spectroscopy) detects light emitted by excited atoms/ions and is best for major and minor elements; it is simpler, less expensive, and more tolerant of high salt samples. ICP-MS (mass spectrometry) measures ions by mass and is 100–1000 times more sensitive, ideal for ultra-trace analysis and isotope ratio work. ICP-MS can measure isotopes and provides superior selectivity but requires more careful sample preparation and instrument tuning.
Why do many ICP methods require acid digestion of solid samples?
Solid samples (rocks, soil, tissue) must be dissolved to introduce elements into the liquid aerosol for aspiration into the plasma. Acid digestion (typically with nitric, hydrochloric, or perchloric acid) converts all elements into ionic form in solution. Incomplete digestion leaves residual solids that clog the nebulizer, reduce sensitivity, and generate false results.
What is matrix suppression, and how do I correct for it?
Matrix suppression occurs when high concentrations of major elements (calcium, magnesium, sodium) in the sample reduce ionization efficiency of trace elements, suppressing their signals. Correction methods include diluting the sample to reduce matrix concentration, using internal standards (spiking the sample with a non-interfering element of similar ionization behavior), or applying matrix-matched calibration curves made from standards containing similar matrix components.
What are polyatomic ion interferences in ICP-MS?
Polyatomic ions (e.g., ArO+, O2+) formed in the plasma can have mass-to-charge ratios identical to analyte ions, causing false positive signals. Common examples include 40Ar-16O+ (mass 56) interfering with Fe+56, and 40Ar-12C+ interfering with Ca+52. Mitigation strategies include using cool plasma conditions, high-resolution mass analyzers (sector instruments), or collision/reaction cells that selectively remove interfering ions.
Can ICP be used to analyze organic samples?
Organic compounds are generally not directly detectable by ICP-OES or ICP-MS because they do not contain multiple atoms suitable for emission or ionization. However, elements within organic molecules (metals bound to organic ligands, phosphorus in phospholipids, sulfur in proteins) can be determined after the organic material is destroyed by digestion, converting all elements to their ionic forms.
Sources
- Greenfield, S., Jones, I. L., & Berry, C. T. (1968). High-pressure plasma jet source for use in atomic spectroscopy. Analyst, 93(1108), 694–697. link ↗
- Montaser, A. (Ed.). (2008). Inductively Coupled Plasma Mass Spectrometry (2nd ed.). Wiley-VCH. ISBN: 978-3527606955
- Houk, R. S. (1986). Mass spectrometry of inductively coupled plasma. Analytical Chemistry, 58(1), 97A–105A. link ↗
How to cite this page
ScholarGate. (2026, June 3). Inductively Coupled Plasma Spectrometry. ScholarGate. https://scholargate.app/en/analytical-chemistry/inductively-coupled-plasma
Which method?
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