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 IO(3)(-) 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 IO(3)(-) and other anions commonly present in the milk samples. In order to preconcentrate total I(-)+IO(3)(-) content in the PIS, IO(3)(-) 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(-), IO(3)(-) 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.