Iodine excitation in a dielectric barrier discharge micro-plasma and its determination by optical emission spectrometry

Abstract

A low temperature micro-plasma generated in a dielectric barrier discharge (DBD) was used as a radiation source for the excitation of iodine and its determination by vapor generation-optical emission spectrometry. A piece of ceramic tube served as an excitation chamber to provide a small gas path for introducing a helium stream to generate a DBD micro-plasma by using a neon power supply. Iodine was on-line vaporized by reaction of iodide in sample solution (or iodate pre-reduced to iodide by ascorbic acid) with H₂O₂. The vapor was subsequently separated and transferred into the DBD excitation chamber by a helium stream for performing optical emission and detection at a 905 nm emission line. The emission spectra were measured with a QE65000 charge-coupled device spectrometer. A few important issues governing the performance of the entire system, e.g., selection of the analytical emission line, elimination of the DBD micro-plasma background variation and optimization of the experimental parameters, were investigated. With a sampling volume of 1.0 mL, a linear range of 0.1–10.0 mg L⁻¹ was obtained along with a detection limit of 0.03 mg L⁻¹. A precision of 2.1% RSD was achieved at the concentration level of 2 mg L⁻¹ iodine. The present system was applied in the determination of trace iodine in real samples, i.e., GBW10023 laver, table salt and cydiodine buccal tablets, giving rise to satisfactory results.