Species dependent iodine extractions in polymer based aqueous biphasic systems: Emerging relations with aggregation number of polymeric micelles

Abstract

A simple, rapid and sensitive spectrophotometric method has been developed for the extraction and speciation of iodine species; periodate (IO4−), iodide (I−) and povidone-iodine. The proposed method is based on aqueous biphasic system (ABS), obtained by mixing 50% aqueous solution of polyethylene glycol (PEG) of molecular weight 6000 with aqueous solution of inorganic salts (1.5M Na2SO4, 1.5M Na3C6H5O7·5H2O and 1M Na2HPO4) respectively at 300K. Haematoxylin (5mM in 50% PEG), was used as sensing agent for periodate (IO4−). The absorption spectra of iodide and povidone-iodine were measured directly in the PEG solution. The molar absorptivity and sandal sensitivity for IO4−, I− and I2 were 45,562L/mol/cm, 288.88L/mol/cm, 27,736L/mol/cm and 4.69μg/cm2, 3.46μg/cm2, 9.1μg/cm2 respectively. The optimum pH of the salt rich phases were evaluated for extraction of iodine species in aqueous biphasic systems. The extraction of iodine species were preferred at neutral (pH=7) or in basic conditions (pH=9–11). The aggregation numbers of the pure PEG solution as well as that after aqueous biphasic extraction at optimum pH of different salt rich phases were monitored by fluorescence quenching method. This work is the first report on the interdependence between percentage of extraction of iodine species in polymer rich phase and its corresponding aggregation number.