Automated tagging of pharmaceutically active thiols under flow conditions using monobromobimane

The thiol-specific derivatization reagent monobromobimane (MBB) is applied - for the first time - under flow conditions. Sequential injection analysis allows the handling of precise volumes of the reagent in the micro-liter range. The effect of the main chemical and instrumental variables was investigated using captopril (CAP), N-acetylcysteine (NAC) and penicillamine (PEN) as representative pharmaceutically active thiols. Previously reported hydrolysis of MBB due to interaction with nucleophilic components of the buffers was avoided kinetically under flow conditions. The proposed analytical scheme is suitable for the fluorimetric determination of thiols at a sampling rate of 36 h−1.