Determination of Total Iodine in Brines and Seawaters by Atmospheric-Pressure Helium Microwave-Induced Plasma Atomic Emission Spectrometry with Continuous-Flow Gas-Phase Sample Introduction

Abstract

Determination of low concentrations of iodine is of great importance in environmental and geochemical analyses. Therefore, the analytical techniques for the determination of iodine in environmental and geochemical samples need to be sensitive. Among the many possible methods, at present, neutron activation analysis is probably the most sensitive technique. On the other hand, in general, although atomic spectrometric techniques are excellent methods for metal determinations, the determination of nonmetals such as iodine by atomic emission spectrometry (AES) as well as atomic absorption spectrometry (AAS) has been quite limited. However, analytical plasmas such as the inductively coupled plasma (ICP) and microwave-induced plasma (MIP) do show promise in the area of nonmetal determinations. The microwave-induced plasma, in particular, has received considerable attention as an excitation source for atomic emission spectrometry. Very recently, the present authors have described the continuous-flow determination of trace iodine by atmospheric-pressure helium MIP-AES using generation of volatile iodine from iodide and reported good detection limits of 2.3 and 3.2 ng/mL for iodine at 183.04 and 206.16 nm, respectively, with linear dynamic ranges of approximately four orders of magnitude in concentration. Of various oxidation reactions examined, an oxidizing solution of 1.0 mM sodium nitrite in 5.0 M sulfuric acid is the most favorable for the generation of elemental iodine from iodide. The aim of this communication is to report the application of atmospheric-pressure helium MIP-AES combined with continuous-flow gas-phase sample introduction to the determination of low concentrations of total iodine (i.e., iodide plus iodate) in brines and coastal seawaters.