Single-Beam Spectrophotometers

In single beam spectrophotometers, a single beam of light passes through the sample holder. The instrument is standardized by placing a reference in the sample holder, and the resulting value is subtracted from subsequent sample measurements to remove effects from the solvent and the cell. The advantages of single-beam instruments are the large dynamic range, simple optics, few moving parts, and compact design. These spectrophotometers are used in applications such as determining the concentration of analyte in solution by measuring the absorbance at a single wavelength and applying the Beer-Lambert Law, and kinetic assays. Single-beam UV-Vis spectrophotometers can measure in the wavelength range 190 to 750 nm (although some go up to 1100). The UV region, considered to be any wavelength less than 340 nm, is useful for measuring nucleic acids, purified proteins, and other organic molecules. An appropriate spectrophotometer depends on sample type and application. Look for a sample volume range that fits your needs, the ability to change samples quickly, an easy-to-read display, and a unit that is easy to clean and maintain.