How Does a Spectrometer Work?

Spectrometers work by passing radiation through a sample to detect a unique spectrum for that sample. The resulting spectrum can be used to identify molecules, functional groups and substances within the sample.

There are four main components of a spectrometer: a source of radiation, a sample, diffraction grating and a detector.

The two types of radiation sources that are used in spectrometers include continuum sources and line sources. Line sources include hollow cathode lamps, while continuum sources include argon lamps, xenon lamps and tungsten lamps. The radiation source chosen depends on the properties of the sample to be analyzed.

The radiation source passes through a wavelength selector. The wavelength is chosen depending on which part of the light spectrum is to be explored. For example, the sample could be analyzed from a specific part of the electromagnetic spectrum including ultraviolet, visible or infrared radiation.

Before the sample is analyzed, a blank is first tested. This is done to zero, or standardize, the results. The sample is then placed into the spectrometer. The radiation passes through a slit to isolate the required wavelength before passing through the sample. Some of this radiation deflects, some passes through and some radiation is absorbed.

The light that passes through the spectrometer is dispersed by a diffraction grating, with the results captured by a specialized instrument called the detector. The detector produces a spectral result, permitting analysts to determine what functional groups, elements and substances are present in the sample.