Ion Mobility Spectrometry of Heavy Metals

A simple, fast, and inexpensive method was developed for detecting heavy metals via the ion mobility spectrometry (IMS) in the negative mode. In this method, Cl⁻ ion produced by the thermal ionization of NaCl is employed as the dopant or the ionizing reagent to ionize heavy metals. In practice, a solution of mixed heavy metals and NaCl salts was directly deposited on a Nichrome filament and electrically heated to vaporize the salts. This produced the IMS spectra of several heavy-metal salts, including CdCl₂, ZnSO₄, NiCl₂, HgSO₄, HgCl₂, PbI₂, and Pb­(Ac)₂. For each heavy metal (M), one or two major peaks were observed, which were attributed to M·Cl^– or [M·NaCl]­Cl^–complexes. The method proved to be useful for the analysis of mixed heavy metals. The absolute detection limits measured for ZnSO₄ and HgSO₄ were 0.1 and 0.05 μg, respectively.