Selective preconcentration and determination of iodine species in milk samples using polymer inclusion sorbent

A method to determine low levels of iodine species namely I− and IO3− in aqueous samples was developed and applied to milk and milk powder samples. It is based on selective preconcentration of I− in polymer inclusion sorbent (PIS) and neutron activation analysis (NAA) of I− sorbed in PIS. The PIS was found to be highly selective for I− in presence of IO3− and other anions commonly present in the milk samples. In order to preconcentrate total I− + IO3− content in the PIS, IO3− was reduced to I− using a mixture of acetic acid and ascorbic acid. It was found that total iodine content in milk could be determined with epithermal neutron activation analysis (ENAA). A scheme was developed to determine I−, IO3− and total iodine. The developed method was applied to milk reference materials (NIST SRM-1549 and IAEA-RM-153 milk powder) and a commercially available milk powder. The scheme for estimation of iodine in different forms was validated by using reference material NIST SRM-1549.