A laboratory technique for measuring substances is spectrophotometry, which quantifies the concentration of a solute in a solution based on its absorbance of light at specific wavelengths. By using a spectrophotometer, researchers can determine how much light a sample absorbs, directly correlating to the substance's concentration. This technique is widely employed in fields such as biochemistry, environmental science, and clinical diagnostics. Spectrophotometry offers precise measurements, facilitating research in areas ranging from enzyme activity to pollutant concentration in water samples.