Solution cathode glow discharge induced vapor generation of iodine for determination by inductively coupled plasma optical emission spectrometry

Abstract

A novel vapor-generation technique is described for iodine determination in aqueous solutions. The iodide and iodate in the solution are converted to volatile iodine vapor through solution cathode glow discharge induced advanced redox processes. It is achieved by in situ produced highly reactive chemical species in the discharge, thereby eliminating the need for externally supplied sources of any redox reagents. Iodine vapor is readily generated from a background electrolyte containing 0.01 mol L⁻¹ HNO_3. The generated iodine vapor is then transported to inductively coupled plasma for determination by optical emission spectrometry. The influences of the background electrolyte, pH, discharge voltage, carrier gas flow rate and ICP power were examined. The detection limits of plasma induced vapor generation for KI and KIO₃ were 0.30 and 0.43 μg L⁻¹, respectively. The repeatability, expressed as the relative standard deviation (n = 11) of a 0.05 mg L⁻¹ standard, was 1.2% for KI and 1.9% for KIO₃. Compared with conventional vapor generation technology, it offers several advantages. First, it eliminates the need for redox regents, and thus minimizes a source of contamination as well as hazards. Second, it is applicable to both iodide and iodate determination. In addition to iodide, iodate could also be directly converted to volatile iodine vapor without prior reduction. The method is sensitive and simple in operation, and requires no auxiliary reagents, served as a useful alternative to conventional vapor generation for trace iodine determination.