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Simultaneous Analysis of Iodine and Bromine Species in Infant Formula using HPLC-ICP-MS.

Research paper by Jenny J Nelson, Lawrence L Pacquette, Shuofei S Dong, Michiko M Yamanaka

Indexed on: 10 Feb '19Published on: 10 Feb '19Published in: Journal of AOAC International



Abstract

A fast and sensitive method for the simultaneous analysis of iodine and bromine species in infant formula was developed using HPLC-inductively coupled plasma-MS (HPLC-ICP-MS). To determine the four halogen species [iodide (I), iodate <inline-formula><mml:math display="inline"><mml:mrow><mml:mo>(</mml:mo><mml:mrow><mml:msubsup><mml:mrow><mml:mi mathvariant="normal">IO</mml:mi></mml:mrow><mml:mn>3</mml:mn><mml:mo>-</mml:mo></mml:msubsup></mml:mrow><mml:mo>)</mml:mo></mml:mrow></mml:math></inline-formula>, bromide (Br), and bromate <inline-formula><mml:math display="inline"><mml:mrow><mml:mo>(</mml:mo><mml:mrow><mml:msubsup><mml:mrow><mml:mi mathvariant="normal">BrO</mml:mi></mml:mrow><mml:mn>3</mml:mn><mml:mo>-</mml:mo></mml:msubsup></mml:mrow><mml:mo>)</mml:mo></mml:mrow></mml:math></inline-formula>] in a milk-based Standard Reference Material and four commercially available infant formula products. The four halogen species were baseline separated in less than 6.5 min using an anion exchange resin column and 5.0 mM NaH₂PO₄ / 15.0 mM Na₂SO₄ / 5.0 mM EDTA (pH 7.0) mobile phase. Following separation, the halogen species were detected by measuring 79 for Br and 127 for I using a triple quadrupole-ICP-MS. The instrument was operated in single quadrupole mode with helium cell gas. Excellent linearity (R = 0.9999 or better) was obtained for all four species with calibration standards ranging from 0 to 100 ppb. The LOD for I, <inline-formula><mml:math display="inline"><mml:msubsup><mml:mrow><mml:mi mathvariant="normal">IO</mml:mi></mml:mrow><mml:mn>3</mml:mn><mml:mo>-</mml:mo></mml:msubsup></mml:math></inline-formula>, Br, and <inline-formula><mml:math display="inline"><mml:msubsup><mml:mrow><mml:mi mathvariant="normal">BrO</mml:mi></mml:mrow><mml:mn>3</mml:mn><mml:mo>-</mml:mo></mml:msubsup></mml:math></inline-formula>were all less than 0.67 μg/kg. To test the suitability of the method for the accurate determination of low concentrations of the four species in infant formula samples, a spike recovery test was carried out at 20 and 40 μg/kg into the diluted infant formula samples. Total elemental determinations of iodine and bromine were also performed using the triple quadrupole-ICP-MS without HPLC.