Colorimetry is a technique that measures the absorbance or transmission of light of a solution or sample at a specific wavelength to determine the concentration of a particular substance in the solution. It is based on the Beer-Lambert law, which states that the absorbance of light by a solution is proportional to the concentration of the absorbing substance in the solution.
In colorimetry, a colorimetric reagent is added to the sample, which reacts with the analyte to produce a colored product. The intensity of the color is directly proportional to the amount of the analyte present in the sample. The wavelength of light used to measure the absorbance is selected based on the specific color produced by the reaction.
Colorimetry has numerous applications in biochemistry, clinical chemistry, and environmental analysis. It is commonly used to measure the concentration of biomolecules such as proteins, nucleic acids, and enzymes. For example, the Bradford assay is a colorimetric method used to determine the concentration of proteins in a sample by measuring the absorbance of the sample at a specific wavelength after reacting with the Bradford reagent. Similarly, the Lowry assay is a colorimetric method used to determine the concentration of proteins in a sample by reacting with copper ions and Folin-Ciocalteu reagent.
Colorimetry is also used in clinical chemistry for the measurement of glucose, cholesterol, and other metabolites in blood and urine samples. In environmental analysis, it is used to measure the concentration of pollutants and contaminants in water and soil samples.