The Folin-Ciocalteu's phenol reagent is widely used in biochemical and analytical chemistry for the quantification of phenolic compounds. It is a key component in the Folin-Ciocalteu assay, which measures the total phenolic content in various samples, including plant extracts, food products, and biological fluids. This reagent reacts with phenols to produce a blue-colored complex, the intensity of which can be measured spectrophotometrically to determine the concentration of phenols.

In the food industry, it is employed to assess the antioxidant capacity of foods and beverages, such as wines, teas, and fruits, as phenolic compounds are often associated with antioxidant properties. In pharmaceutical research, it is used to evaluate the phenolic content in herbal medicines and natural products, aiding in quality control and standardization. Additionally, it finds applications in environmental studies to analyze phenolic pollutants in water and soil samples. Its simplicity, sensitivity, and reliability make it a popular choice for phenolic compound analysis across various fields.