Term: double-wavelength spectroscopy
https://doi.org/10.1351/goldbook.D01854

Definition:
The effect of spectral background due to impurities, solvent or radiation scattering may be reduced if the difference in the absorbances of a sample measured at two selected wavelengths is obtained. This is often achieved by repetitively switching from one wavelength to the other. Double-wavelength spectroscopy does this automatically by allowing two beams of radiation of different wavelengths to pass through the cell. One beam is fixed at a longer wavelength and the other measures absorbance while being scanned over a limited wavelength range at shorter wavelengths.

Related Terms:
1) scattering (http://doi.org/10.1351/goldbook.S05487).
2) wavelength (http://doi.org/10.1351/goldbook.W06659).
3) spectroscopy (http://doi.org/10.1351/goldbook.S05848).
4) absorbance (http://doi.org/10.1351/goldbook.A00028).

Source: PAC, 1988, 60, 1449. 'Nomenclature, symbols, units and their usage in spectrochemical analysis - VII. Molecular absorption spectroscopy, ultraviolet and visible (UV/VIS) (Recommendations 1988)' on page 1455 (https://doi.org/10.1351/pac198860091449)

Citation: 'double-wavelength spectroscopy' in IUPAC Compendium of Chemical Terminology, 5th ed. International Union of Pure and Applied Chemistry; 2025. Online version 5.0.0, 2025. https://doi.org/10.1351/goldbook.D01854

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