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

Background: 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). Method: 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. Results: 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 m/z 79 for Br and m/z 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. Conclusions: Total elemental determinations of iodine and bromine were also performed using the triple quadrupole-ICP-MS without HPLC.