Cysteine, despite its low abundance, demonstrates significant functional versatility. Its thiol group (–SH) can undergo sequential oxidation by reactive oxygen species (ROS), progressing through sulfenation (–SOH) and sulfination (–SO₂H) to ultimately form irreversible sulfonation (–SO₃H). Sulfonation introduces a substantial, negatively charged moiety that modifies the residue's charge distribution, steric properties, and local interactions, consequently impacting protein conformation and function. This modification serves as a biomarker for oxidative stress and is linked to neurodegenerative diseases, myocardial ischemia/reperfusion injury, genetic deficiencies, and the aging process. Existing enrichment and quantification methodologies can only identify a restricted number of sulfonation sites. Our method, utilizing a magnetic resin functionalized with pyridyl disulfide groups, facilitates the efficient enrichment of thiol-containing peptides. Following release, these peptides are oxidized to produce sulfonated peptides, which serve as internal standards. This, in conjunction with dimethyl labeling, permits large-scale quantification of sulfonation.