Phenyl isothiocyanate is widely used in biochemistry for protein sequencing, particularly in the Edman degradation process. It reacts with the N-terminal amino acid of a peptide, enabling step-by-step identification of amino acids in a protein chain. This makes it a critical reagent in proteomics and molecular biology research. Additionally, it serves as a derivatization agent in chromatography to enhance the detection and separation of compounds. In organic synthesis, it is employed as a building block for synthesizing heterocyclic compounds and pharmaceuticals. Its applications also extend to material science, where it is used to modify surfaces or polymers for specific functional properties.