Atoms or molecules that are excited to high energy levels can decay to lower levels by emitting radiation (emission or luminescence). For atoms excited by a high-temperature energy source this light emission is commonly called atomic or optical emission (atomic-emission spectroscopy,) and for atoms excited with light it is called atomic fluorescence (atomic-fluorescence spectroscopy.)
Atomic-emission spectroscopy (AES) uses quantitative measurement of the optical emission from excited atoms to determine analyte concentration. Analyte atoms in solution are aspirated into the excitation region where they are desolvated, vaporized and atomized by a flame, discharge, or plasma. These high-temperature atomization sources provide sufficient energy to promote the atoms into high energy levels. The atoms decay back to lower levels by emitting light.
In a highly sophisticated setup, sample preparation for the AES is conducted using inductively coupled plasma (ICP) and this technique requires relatively high flow rates of specialty gases grades of HiQ Argon, which would often be supplied as multiple cylinder bundles or supplied as liquid and vapourised before use in the instrument to ensure uninterrupted operation of the ICP. The typical argon purity level would be 99.998 to 99.999%.
Inductively Coupled Plasma - Atomic Emission Spectroscopy (ICP - AES)
Detection limit |
Gas recommendation |
Regulator recommendation |
Gas generator recommendation |
| Purge gas | |||
| ≤ 100 ppb | HiQ Argon 5.0 | BASELINE C106 series | n/a |
| ≤ 100 ppb | HiQ Nitrogen 5.0 | BASELINE C106 series | HiQ MISTRAL Nitrogen |
| Shear gas | |||
| ≤ 100 ppb | HiQ Air 4.0 | BASELINE C106 series | HiQ Zero Air |
| ≤ 100 ppb | HiQ Nitrogen 4.6 | BASELINE C106 series | HiQ MISTRAL Nitrogen |
| Torch gas | |||
| ≤ 100 ppb | HiQ Argon 4.8 | BASELINE C106 series | n/a |
Alternatively, AES can be combined with gas chromatography (GC) where the technique would be referred to GC-AED. The chromatograph would consume HiQ Helium 6.0 (purity level 99.9999%) for the AED plasma and as carrier gas to allow species identification in the atomic emission detector.
AES employing a flame, also called flame emission spectroscopy (FES) or flame photometry, has found widespread application in elemental analysis. It can be used for both quantitative and qualitative analysis and it is a single element method. Its most important uses are in the determination of sodium, potassium, lithium and calcium in biological fluids and tissues.
Emission Spectrometry - Instrumentation
The sample must be converted to free atoms, usually in a high-temperature excitation source e.g., a flame. Liquid samples are nebulized and carried into the flame by a flowing gas. The excitation source must desolvate, atomize and excite the analyte atoms. The flame supplies the sufficient energy to promote the atoms into high energy levels.
As the atoms decay to their ground stage, the emitted radiation passes through the monochromator that isolates the specific wavelength for desired analysis. A photodetector measures the radiant power of the selected radiation.