Determination of Iodine and Bromine Compounds by Ion Chromatography/Dynamic Reaction Cell Inductively Coupled Plasma Mass Spectrometry
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An inductively coupled plasma mass spectrometer (ICP-MS) was used as an ion chromatographic detector for the speciation of iodine and bromine. Gradient elution using NH<sub>4</sub>NO<sub>3</sub> at pH 10 allowed the chromatographic separation of ionic iodine (I<sup>-</sup> and IO<sub>3</sub><sup>-</sup>) and bromine (Br<sup>-</sup> and BrO<sub>3</sub><sup>-</sup>) species in less than 8 min. Effluents from the ion-exchange column were delivered to the nebulization system of ICP-MS for the determination of I and Br. The potentially interfering <sup>38</sup>Ar<sup>40</sup>ArH<sup>+</sup> and <sup>40</sup>Ar<sup>40</sup>ArH<sup>+</sup> at the bromine masses <i>m/z</i> 79 and 81 were significantly reduced in intensity (by approximately two orders of magnitude) by using 0.6 mL min<sup>-1</sup> O<sub>2</sub> as a reactive cell gas in the dynamic reaction cell (DRC). Moreover, the signal-to-background ratio at iodine mass <i>m/z</i> 127 increased significantly when O<sub>2</sub> was used as the reaction gas. The detection limits were in the range of 0.001 - 0.002 and 0.03 - 0.04 ng mL<sup>-1</sup> for various I and Br compounds, respectively, based on the peak height. The relative standard deviation of the peak areas for five injections of a 2 ng mL<sup>-1</sup> I<sup>-</sup>, IO<sub>3</sub><sup>-</sup> and 20 ng mL<sup>-1</sup> Br<sup>-</sup>, BrO<sub>3</sub><sup>-</sup> mixture was in the range of 3 - 4%. The concentrations of I and Br compounds have been determined in selected water and urine samples. The spike recoveries were in the range of 94 - 102% for all of the determinations. This method has also been applied to determine various I and Br compounds in an NIST RM 8435 whole-milk powder reference material and a seaweed sample obtained locally. A microwave-assisted extraction method was used to extract these compounds, which were quantitatively leached with a 10% mass/volume (m/v) tetramethylammonium hydroxide (TMAH) solution in a focused microwave field within a period of 6 min. The major components of I and Br in milk powder and seaweed were I<sup>-</sup> and Br<sup>-</sup>.
- Analytical Sciences
Analytical Sciences 24(4), 509-514, 2008-04-10
The Japan Society for Analytical Chemistry