spectrophotometrically

Spectrophotometry is the quantitative measurement of how much light a chemical substance absorbs as a function of wavelength. When a measurement is performed spectrophotometrically, a sample is placed in a spectrophotometer, and the instrument records the intensity of light transmitted through or absorbed by the sample across a defined spectral range, typically in the ultraviolet and visible regions (UV-Vis). The resulting data can be related to concentration in accordance with the Beer-Lambert law, A = εlc, where A is absorbance, ε is molar absorptivity, l is optical path length, and c is concentration. Absorbance is related to transmittance by A = -log10(T).

Modern spectrophotometers use a light source, wavelength selector, and detector to measure absorbance or transmittance at chosen wavelengths. Measurements often require calibration with standards and a blank to correct for baseline signals. Common formats include single-wavelength measurements and full spectral scans. Applications span chemistry, biochemistry, environmental analysis, food and pharmaceutical fields, and clinical chemistry, including routine concentration determinations, kinetic studies, and enzymatic or binding assays.

Limitations include dependence on a chromophore that absorbs at accessible wavelengths, potential interference from sample matrix, turbidity or scattering, stray light, and nonlinearity outside the instrument’s linear range. Derivative or multi-wavelength techniques can enhance selectivity. The term spectrophotometrically denotes that the measurement is carried out using spectrophotometry rather than alternative analytical methods.