A new approach in tandem mass spectrometric simultaneous determination of perchlorate, thiocyanate, and iodide using their ternary complexes with tris(1,10-phenanthroline)iron(II) chelate

A rapid and sensitive method was developed for simultaneous determination of perchlorate (ClO₄ ⁻), thiocyanate (SCN⁻), and iodide (I⁻). The ions were reacted with tris(1,10-phenanthroline)iron(II) chelating cation, [Fe(phen)₃]²⁺, to produce their ternary complexes, [Fe(phen)₂ClO₄]⁺, [Fe(phen)₂SCN]⁺, and [Fe(phen)₂I]⁺ that were extracted together with nitrobenzene. Five microliters of the extract was injected directly into an electrospray ionization tandem mass spectrometer. Quantification of ClO₄ ⁻, SCN⁻, and I⁻ was performed by selected reaction monitoring of the product ion [Fe(phen)O₂]⁺ at m/z 268 that derived from the precursor ion [Fe(phen)₂ClO₄]⁺ at m/z 515, the product ion [Fe(phen)SCN]⁺ at m/z 294 that derived from precursor ion [Fe(phen)₂SCN]⁺ at m/z 474, and the product ion [Fe(phen)I]⁺ at m/z 363 that derived from precursor ion [Fe(phen)₂I]⁺ at m/z 543, respectively. Perchlorate, SCN⁻, and I⁻ were measured in the range of 0.1–10 μM with the limits of detection at 0.03 μM by using a 50-μl sample aliquot containing the three ions within 10 min. The SCN⁻ level in gastric fluid of a victim of NaCN poisoning was 137 ± 23 μM, which is slightly higher than the results from control subjects (n = 7), 72 ± 39 μM.