Disulfiram (DSF) is used in the treatment of recovering alcoholics and exerts its effect by inhibiting the enzyme aldehyde dehydrogenase (ALDH). We analyzed a mixture of products derived photochemically from DSF with on-line microbore HPLC-continuous-flow liquid secondary ion mass spectrometry (HPLC-CF-LSI-MS). By utilizing the post-HPLC column split of solvent flow, a small proportion (ca. 5%) was sent directly into the mass spectrometer, and the remainder was collected. Simultaneous MS analysis and enzyme inhibition studies on ALDH were then possible. Furthermore, using HPLC-CF-LSI-MS-MS, we were able to structurally characterize an interesting sulfine compound that inhibited ALDH.