{"term":{"id":"14104","title":"absorbance assay","longtitle":"IUPAC Gold Book - absorbance assay","doi":"10.1351\/goldbook.14104","code":"14104","status":"current","synonym":"<em>synonym<\/em>: optical density assay (obsolete)","definitions":[{"id":1,"text":"Assay in which response is determined by the detection of light absorption by an assay component.","notes":{"1":"The concentration of the absorbing species can be quantified using the Beer–Lambert law (or Beer–Lambert–Bouguer law) \\[A = \\varepsilon cl = \\lg\\left(\\frac{P_{0}}{P}\\right)\\] where \\(\\varepsilon\\) is the molar absorption coefficient of the absorbing species, \\(l\\) is the absorption path length, and \\(c\\) the amount concentration. A sample is irradiated with a specific wavelength of light, typically in the ultraviolet or visible spectral region; the spectral radiant power of incident light on the sample (\\(P_{0}\\)) and transmitted radiation after passing through the sample (\\(P\\)) are used to calculate absorbance (\\(A\\))."},"sources":["PAC, 2011, 83, 1129. 'Glossary of terms used in biomolecular screening (IUPAC Recommendations 2011)' on page 1130 (https:\/\/doi.org\/10.1351\/PAC-REC-09-05-03)"]}],"altoutputs":{"html":"https:\/\/goldbook.iupac.org\/terms\/view\/14104\/html","xml":"https:\/\/goldbook.iupac.org\/terms\/view\/14104\/xml","plain":"https:\/\/goldbook.iupac.org\/terms\/view\/14104\/plain"},"citation":"Citation: 'absorbance assay' in IUPAC Compendium of Chemical Terminology, 5th ed. International Union of Pure and Applied Chemistry; 2025. Online version 5.0.0, 2025. 10.1351\/goldbook.14104","license":"The IUPAC Gold Book is licensed under Creative Commons Attribution-ShareAlike CC BY-SA 4.0 International (https:\/\/creativecommons.org\/licenses\/by-sa\/4.0\/) for individual terms.","collection":"If you are interested in licensing the Gold Book for commercial use, please contact the IUPAC Executive Director at executivedirector@iupac.org .","disclaimer":"The International Union of Pure and Applied Chemistry (IUPAC) is continuously reviewing and, where needed, updating terms in the Compendium of Chemical Terminology (the IUPAC Gold Book). Users of these terms are encouraged to include the version of a term with its use and to check regularly for updates to term definitions that you are using.","accessed":"2026-05-09T11:09:56+00:00"}}