A solution for test iodine in infant milk powder - Food and Beverage
Iodine, a kind of common microelement, is usually added in infant milk power at microgram level, but it plays important role in infant growth and development. It impedes the growth of infant with insufficient or redundant dosage, for example it causes mental deficiency with less iodine however, it also causes thyroid problem with excess intake. Hence， there is strict limit for the addition of iodine in milk powder. The China nation standard GB14880-94 regulated that iodine or iodate is allowed for 250-680μg/kg in baby food and 30-150μg in 100g milk or rice powder. Iodine exists in the form of Iodine 127 isotope and it’s detectable with in measurable range of spectrum. However it’s added in iodate form in nourishment and binding with protein or other ingredients. Once the sample decomposes, iodine is very volatile and gets lost. This adds up difficulty of pretreatment of iodine-containing sample.
The application of microwave digestion with ICP-MS is easy to test iodine in a fast way. It's not only accurate but also repeatable.
TOPEX microwave digestion system(Preekem Scientific)
- 1000ug/L Iodine solution ( NIST calibrated ) ;
- 10mg/L Te formed by 2% HN03 and trace HF ( NIST calibrated ) ;
- 29.8% ammonia water ( GR } ;
- 67%HN03(GR); Triton X-100 surfactant; Super pure water
Weigh 0.2g milk powder into KJ-100 vessel, then add 0.5ml 10mg/LTeas internal standard and 2.5mlHN03, then load the vessel to cavity to run it to 190 deg and keep for 10 minutes. After digestion, cool until room temperature and open the vessel. Transfer the solution then add 10mL ammonia water and 2.5mL Triton X-100; constant volume to 50mL. Use ICP-MS to test empty sample and calculate recovery.
2.Results and discussion
KJ-100 is a closed type digestion vessel, it could guarantee no loss of volatile element especially iodine. All the results showed good recovery with more than 85%. The method is easy to handle and accuracy is guaranteed