Colorimeter

A colorimeter is an analytical instrument that measures the concentration of colored compounds in a solution by assessing how much light is absorbed or transmitted at a specific wavelength.

Its operation relies on Beer-Lambert law, which relates absorbance to concentration via A = εcl. A light source emits light that passes through a cuvette containing the sample; a detector on the opposite side measures transmitted light. The decrease in light intensity is related to the amount of colored species in the solution.

Most colorimeters use fixed-wavelength filters to select a particular wavelength. More advanced instruments called spectrophotometers measure across a range of wavelengths, providing broader spectral data; some devices marketed as colorimeters may include digital sensors and LED sources.

Calibration and blanking: The instrument is calibrated with standards of known concentration and a blank solution to set 0 absorbance. The measured absorbance is converted to concentration using a calibration curve.

Applications: clinical chemistry for assays like glucose or bilirubin, environmental testing for nitrates, nitrites, and color in water, food and beverage analysis, and industrial process control.

Limitations: colorimeters require clear, non-turbid samples; strongly colored samples or high turbidity can interfere with accurate measurements; results depend on proper calibration, appropriate reagents, and correct path length.