Profile Analysis of Iodine in Powdered Infant Formula and Infant Complementary Foods by Inductively Coupled Plasma Mass Spectrometry

Background: Both iodine deficiency and excessive iodine intake are very detrimental to the development of the baby, it is necessary to accurately measure the iodine content in infant milk powder. A probing study to establish a reliable and robust method for determining the iodine concentration using the inductively coupled plasma mass spectrometry was performed in combination with a sample digestion step.

Methods: A sample was digested in 5% tetramethylammonium hydroxide at 85°C. This method adopted a shorter extraction time (3h) and used 186Re as the internal standard, which exhibited greater stability in infant foods. The linearity range (R2) was >0.998, limit of detection was 0.01 mg kg-1, limit of quantification was 0.03 mg kg-1, relative standard deviation was less than 4%, and recovery range was 94.8%–109%.

Results: The accuracy of the optimized method was evaluated by testing standard reference material SRM 1849a, and the results (1.17 ± 0.05 mg kg-1, n = 6) were in good agreement with the certified value (1.29 ± 0.11 mg kg-1).

Conclusions: The results of the validation process confirmed that ICP-MS is the gold standard for determination of low iodine concentrations in infant foods. In addition, profiling the iodine content of different infant foods allows the development of a rational diet for infants to promote healthy development.

Keywords: Iodine, Inductively Coupled Plasma Mass Spectrometry, Tetramethylammonium Hydroxide, Powdered Infant Formula, Matrix.