Glutathionylation is an important post-translational modification and developing tools to identify which cysteine residues on proteins are glutathionylated in response to different physiological conditions is necessary. This project utilizes an approach consisting of azido-glutathione, a single purified protein, and an oxidant to form disulfide bonds between the azide modified glutathione and the cysteine residues of the protein. After this the reaction is quenched with iodoacetamide, subjected to a click reaction with a chemically cleavable alkyne conjugated biotin, and digested with trypsin. These peptide fragments are eluted from streptavidin beads and subjected to LC-MS/MS to determine which cysteine residues are glutathionylated in-vitro.