Spectrophotometry

Spectrophotometry measures how much light a sample transmits or absorbs at selected wavelengths. Its measurements can reveal a material’s concentration, composition, or optical properties.

Beer–Lambert law: A law relating a material’s absorbance to its concentration, path length, and molar absorptivity. It converts absorbance measurements into concentrations when its assumptions hold.
UV–visible spectroscopy: A spectroscopic method that measures absorption of ultraviolet and visible light. It is the most common spectrophotometric approach for solution analysis.
Electromagnetic spectrum: The full range of electromagnetic radiation, ordered by frequency or wavelength. Spectrophotometry probes selected regions of this broader spectrum.
Spectroscopy: The study of interactions between matter and electromagnetic radiation as a function of wavelength or frequency. Spectrophotometry is one measurement-based branch of this broader field.
Stray light: Unwanted light reaching a detector outside the intended optical path or wavelength band. It can cause substantial errors when measuring highly absorbing samples.
Absorbance: A logarithmic measure of how much light a sample absorbs at a specified wavelength. It expresses the sample’s light loss in the quantity commonly measured.
Nucleic acid quantification: The estimation of DNA or RNA concentration from an analytical measurement. Absorbance near 260 nanometers provides a rapid concentration estimate.
Wavelength: The distance between successive corresponding points of a wave. Wavelength selection determines which optical transitions are measured.
Fluorescence spectroscopy: A method that measures light emitted by a sample after optical excitation. It detects emitted light rather than only measuring transmitted or absorbed light.
Spectral bandwidth: The range of wavelengths passed by an optical system around a selected wavelength. A broad bandwidth can blur narrow spectral features and distort absorbance.

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