Ali MOGHIMI - Department of Chemistry, East Tehran(Ghiam Dasht) Campus Islamic Azad University, Tehran, Iran
Samaneh AGHAJANI - Department of Chemistry, Pishva Varamin Branch Islamic Azad University, Varamin, Iran
Mostafa SHOJAI - Department of Chemistry, Pishva Varamin Branch Islamic Azad University, Varamin, Iran

A sensitive, selective and rapid method has been developed for the determination μg l-1 level of cobalt based on the rapid reaction of cobalt(II) with Isopropyl 2-[(isopropoxy carbothioyl) disulfanyl] ethanethioate chelate (IIDE)and the solid phase extraction (SPE) of the colored chelate with Waters Porapak Sep-Park C18 disk. The Isopropyl 2-[(isopropoxy carbothioyl) disulfanyl]ethanethioate chelate can react with Co(II) in the presence of pH 4.2 acetic acid -/sodium acetate buffer solution and cetyl trimethylammonium bromide (CTMAB) medium to form a violet chelate of a molar ratio 1:2 (cobalt to Isopropyl 2-[(isopropoxy carbothioyl) disulfanyl]ethanethioate chelate. This chelate can retained on Waters Porapak Sep-Park C18 disk quantitatively when they passed the disk as aqueous solution. After the enrichment finished, the retained chelate can be eluted from disk by 2.5 ml of ethanol (contain 5% acetic acid). In the measured solution, the molar absorptivity of the chelate is 1.58×/105 1 mol -1 cm-1at 635 nm, and Beer s law is obeyed in the range of 0.01-/0.4 μg ml-1. The relative standard deviation for 11 replicate sample of 0.01 μg.ml-1 level is 2.54%. The detection limit is 0.01 μg ml-1 (in original samples). This method can be applied to the determination of μg ml-1 level of cobalt in drinking water with satisfactory results.

Cobalt; Solid phase extraction spectrophotometry; Isopropyl 2-[(isopropoxy carbothioyl) disulfanyl] ethanethioate chelate(IIDE)