Optimization of a Monobromobimane (MBB) Derivatization and RP-HPLC-FLD Detection Method for Sulfur Species Measurement in Human Serum after Sulfur Inhalation Treatment

(1) Background: Hydrogen sulfide (H(2)S) is a widely recognized gasotransmitter, with key roles in physiological and pathological processes. The accurate quantification of H(2)S and reactive sulfur species (RSS) may hold important implications for the diagnosis and prognosis of diseases. However, H(2)S species quantification in biological matrices is still a challenge. Among the sulfide detection methods, monobromobimane (MBB) derivatization coupled with reversed phase high-performance liquid chromatography (RP-HPLC) is one of the most reported. However, it is characterized by a complex preparation and time-consuming process, which may alter the actual H(2)S level; moreover, a quantitative validation has still not been described. (2) Methods: We developed and validated an improved analytical protocol for the MBB RP-HPLC method. MBB concentration, temperature and sample handling were optimized, and the calibration method was validated using leave-one-out cross-validation and tested in a clinical setting. (3) Results: The method shows high sensitivity and allows the quantification of H(2)S species, with a limit of detection of 0.5 µM. Finally, it can be successfully applied in measurements of H(2)S levels in the serum of patients subjected to inhalation with vapors rich in H(2)S. (4) Conclusions: These data demonstrate that the proposed method is precise and reliable for measuring H(2)S species in biological matrices and can be used to provide key insights into the etiopathogenesis of several diseases and sulfur-based treatments.