UVVisspektroskopialla

UVVisspektroskopialla is an analytical technique used to study electronic transitions in molecules by measuring their interaction with ultraviolet and visible light (approximately 200–800 nm). The resulting spectra, plots of absorbance versus wavelength, provide qualitative and quantitative information about chemical species with chromophores or conjugated systems.

Principle and instrumentation: A broadband light source emits light that passes through a sample. A monochromator selects a narrow wavelength, and a detector measures the transmitted light. The instrument is often configured as a spectrophotometer, with single-beam or dual-beam arrangements; modern instruments frequently use diode-array detectors for rapid spectral acquisition. A cuvette containing the sample sits in the light path; solvents and blanks are used for baseline correction.

Data and analysis: The instrument records absorbance A = log10(I0/I). By Beer-Lambert law, A = εcl, where ε is molar absorptivity, c is concentration, and l is path length. Calibration against standards yields quantitative results; spectra identify functional groups and chromophores through characteristic bands.

Applications: Pharmaceutical assay, environmental monitoring, food and beverage analysis, proteomics, and kinetics studies. The technique is fast, non-destructive, requires relatively small sample volumes, and can be automated.

Limitations and considerations: UV absorption by solvents or water limits the usable window; colorless samples may require derivatization; interfering species, scattering, or turbidity can affect results. For solids, diffuse reflectance or sample preparation may be used; accuracy depends on proper baseline correction and path-length calibration.