Customer Focus: Optical Emission Spectroscopy, or OES, is a well trusted and widely used analytical technique used to determine the elemental composition of a broad range of metals. The part of the electromagnetic spectrum which is used by OES includes the visible spectrum and part of the ultraviolet spectrum. In terms of wavelength, that is from 130 nanometers up to around 800 nanometers.
All OES analyzers contain three major components. The first is an electrical source to excite atoms within a metallic sample so that they emit characteristic light (or optical emission). A small part of the sample is heated to thousands of degrees Celsius. This is done using an electrical high voltage source in the spectrometer via an electrode. The difference in electrical potential between the sample and electrode produces an electrical discharge, this discharge passes through the sample, heating and vaporizing the material at the surface and exciting the atoms of the material, which then emits the element-characteristic emission lines.
The second component is an optical system. The light, the multiple optical emission lines from the vaporized sample known as a plasma pass into the spectrometer. A diffraction grading in the spectrometer separates the incoming light into element-specific wavelengths and a corresponding detector measures the intensity of light for each wavelength. The intensity measured is proportional to the concentration of the element in the sample. The third component is a computer system. The computer system acquires the measured intensities and processes this data via a predefined calibration to produce elemental concentrations.
Compared to other analytical techniques, OES has many advantages: it’s fast and relatively easy to use, it measures a wide range of elements and concentrations in many different types of materials. It is extremely accurate when measuring low levels of trace and tramp elements, and it’s fairly low-cost compared to other techniques.