Study on Determination of Trace Cobalt in Environmental Water Samples after Separation/Enrichment Using Microcrystalline Phenolphthalein Modified with 8-Hydroxyquinoline

The paper presents a novel method for the separation/enrichment of trace Co2+ using microcrystalline phenolphthalein modified with 8-hydroxyquinoline (HQ) prior to the determination by spectrophotometry. The effects of different parameters,such as the dosages of phenolphthalein and HQ,various salts and acidity on the enrichment yield of Co2+ have been investigated to select the experimental conditions. The possible enrichment mechanism of Co2+ was discussed.The results showed that under the optimum conditions, Co2+ could be quantificationally adsorbed on the surface of microcrystalline phenolphthalein in the form of the chelate precipitate of Co(HQ)2 ,while K+,Na+,Ca2+,Mg2+,Cd2+,Zn2+,Mn2+,Fe2+ and Al3+ could not be adsorbed at all.Therefore,Co2+ was completely separated from the above metal ions in the solution. A new method for the spectrophotometric determination of trace cobalt after separation/enrichment using microcrystalline phenolphthalein modified with 8-hydroxyquinoline was established.The proposed method has been successfully applied to the determination of Co2+ in various environmental water samples, and the results agreed well with those obtained by FAAS method.