Determination of trace iron in seawater by cloud point extraction coupled with orthophenanthroline spectrophotometry

A determination method of trace iron in seawater by cloud point extraction-spectrophotometry was established using orthophenanthroline(Phen) as coloring reagent and polyethylene glycol 6000(PEG6000) as surfactant.This method was based on the cloud point phenomenon of surfactant.Fe2+ could form stable complex Fe(Phen)32+ with Phen,which was then quantitatively extracted into micellar-rich phase,realizing the separation from matrix.The extraction phase was properly treated and determined by spectrophotometry.The effect of coloring reagent concentration,coloring temperature,extraction time and the dosage of PEG6000 on the determination sensitivity of cloud point extraction-spectrophotometry was investigated.Under the optimal conditions,the detection limit of iron was 4.1×10-3 μg/mL(the concentration factor of 18).The proposed method had been applied to the determination of trace iron in seawater.The results were consistent with those obtained by ICP-AES,the relative standard deviations(RSD) were 3.8 %-4.5 %,and the recovery of standard addition were 86 %-95 %.