WHAT IT IS
Inductively Coupled Plasma Optical Emission Spectrometry (ICP-OES), also known as ICP-Atomic Emission Spectrometry (ICP-AES), is an analytical technique uses a high-temperature plasma to excite atoms and ions, which then emit light at characteristic wavelengths. It used for elemental identification and quantification and enables simultaneous, multi-element detection of metals and some non-metals at trace and major levels.
HOW IT WORKS
In ICP-OES, a liquid sample is introduced into a high-temperature plasmagenerated by a radiofrequency (RF) coil surrounding a stream of argon gas. The sample is nebulized into an aerosol and transported into the plasma, where the high energy causes atomization and excitation of atoms and ions.
As these excited species return to lower energy states, they emit light at element-specific wavelengths. This light is collected and directed into a spectrometer, where a diffraction grating or echelle optics separates it into its component wavelengths.
The emitted light intensities are measured by detectors such as photomultiplier tubes or charge-coupled devices (CCDs). Each element emits light at characteristic wavelengths, allowing for qualitative identification and quantitative determination based on the emission intensity.
ADVANTAGES
Multi-Element Capability: Simultaneous detection of more than 70 elements in a single run significantly enhances efficiency.
Wide Linear Dynamic Range: Accurate quantification across concentrations ranging from sub-ppb (parts per billion) to percent levels.
High Sensitivity: Sufficient for most environmental and industrial applications, with detection limits typically in the low ppb range.
High Throughput: Rapid analysis and short measurement times (typically seconds per element) support high sample volumes.
Minimal Chemical Interference: High plasma temperature minimizes matrix effects and improves reliability.
Stability and Reproducibility: The plasma provides a stable excitation source, leading to consistent results over long sequences.
CHALLENGES AND LIMITATIONS
Spectral Overlap: Emission lines from different elements can overlap, especially in complex samples; careful method development or mathematical correction is required.
Lower Sensitivity than ICP-MS: For ultra-trace detection (below ppb), ICP-MS is preferred.
Sample Preparation: Requires digestion of solid samples into clear solutions; acid digestion protocols must be optimized to avoid contamination or loss.
Argon Gas Consumption: Plasma generation requires a continuous supply of high-purity argon, adding to operating costs.
Matrix Effects: High dissolved solids or complex matrices can affect nebulization and signal response.