UV-Vis spectrophotometry fundamentals

UV-Visible spectrophotometry measures how much light a sample absorbs across ultraviolet and visible wavelengths (typically 190–1100 nm). Absorbance relates to concentration through the Beer–Lambert law (A = εcl).

Common uses

• Nucleic acid and protein quantitation (260/280 nm).
• Enzyme kinetics and assay endpoints.
• Concentration of coloured solutions and purity checks.

Single vs double beam

Double-beam instruments compare sample and reference simultaneously, correcting for lamp drift — preferred for kinetics and demanding QC. Single-beam units are cheaper and adequate for routine endpoint reads.