Inductively Coupled Plasma Atomic Emission spectroscopy (ICP-AES) is one of the most powerful and popular analytical tools for the determination of trace elements. The technique is based upon the spontaneous emission of photons from atoms and ions that have been excited. Liquid and gas samples may be injected directly into the instrument, while solid samples require extraction or acid digestion so that the analytes will be present in a solution. The sample solution is converted to an aerosol and directed into the central channel of the plasma.
The segmented array detector allows multiple elements to be analyzed simultaneously, while the dual-view torch configuration allows software controlled switching between axian or radial plasma torch viewing positions to either increase sensitivity or decrease interference effects.
At its core the inductively coupled plasma (ICP) sustains a temperature of approximately 10 000 K, so the aerosol is instantly vaporized. The elements are liberated as free atoms in the gas state. Sufficient energy is often available to convert the atoms to ions and subsequently promote the ions to excited states. Both the atomic and ionic excited state species may then relax to the ground state via the emission of a photon. These photons have characteristic energies that are determined by the energy level structure for the atoms or ions. The wavelength of the photons can be used to identify the elements from which they originated. The total number of photons is directly proportional to the concentration of the originating element in the sample.
Various applications of identifying low-level contaminants via ICP-OES include:
- Agricultural and food - Animal tissues, beverages, feeds, fertilizers, garlic, nutrients, pesticides, plant materials, rice flour, soils, vegetables, wheat flour
- Biological and clinical - Brain tissue, blood, bone, bovine liver, feces, fishes, milk powder, orchard leaves, pharmaceuticals, pollen, serum, urine
- Geological - Coal, minerals, fossils, fossil fuel, ore, rocks, sediments, soils, water
- Environmental and water - Brines, coal fly ash, drinking water, dust, mineral water, municipal wastewater, plating bath, sewage sludge, slags, seawater, soil
- Metals Alloys - Aluminum, high-purity metals, iron, precious metals, solders, steel, tin
- Organic - Adhesives, amino acids, antifreeze, combustion materials, cosmetics, cotton cellulose, dried wood, dyes, elastomers, epoxy, lubricant, organometallic, organophosphates, oils, organic solvent, polymers, sugars
- Other materials - Acids, carbon, catalytic materials, electronics, fiber, film, packaging materials, paints and coatings, phosphates, semiconductors, superconducting materials
