Cloud point extraction with mixed micelles of TX-114/ DOSS and derivative spectrophotometry for simultaneous determination of Fe²⁺ and Co²⁺ using 2,2′,6′,2′′-terpyridine

Abstract

A new cloud point extraction procedure with derivative spectrophotometry for the simultaneous preconcentration and determination of Fe²⁺ and Co²⁺ has been developed. In this method both the Fe²⁺ and Co²⁺ metal ions are simultaneously complexed with 2,2&prime;,6&prime;,2&prime;&prime;-terpyridine at a <em>p</em>H of 3.8. The complexes of Fe²⁺ and Co²⁺ are then extracted into mixed micelles of surfactants (Triton X-114 and docusate sodium salt). Various parameters such as <em>p</em>H, concentration of the ligand, concentrations of the surfactant, concentration of salt (Na₂SO₄), equilibration temperature and time have been optimized. Under optimum conditions, the linear ranges of Fe²⁺ and Co²⁺ are found to be 0.373&ndash;2.42 &micro;g mL^-1 and 3.14&ndash;18.86 &micro;g mL^-1 respectively. Their corresponding limits of detections are found to be 0.498 ng mL^-1 and 4.54 ng mL^-1. The proposed method has been successfully applied to the determination of Fe²⁺ and Co²⁺ in tap water and sea water. The recoveries were found to be in the range of 98&ndash;107%.