Cloud point extraction, preconcentration and spectrophotometric determination of trace amount of manganese(II) in water and food samples

A new cloud point extraction (CPE) process using the nonionic surfactant Triton X-114 to extract manganese(II) from aqueous solution was investigated. The method is based on the complexation reaction of manganese(II) with 1,2,5,8-tetrahydroxyanthracene-9,10-dione (quinalizarin) in the presence of borate buffer at pH 8.5 and micelle-mediated extraction of the complex. The enriched analyte in the surfactant-rich phase was determined by spectrophotometry at 528 nm. The optimal extraction and reaction conditions (e.g. pH, reagent and surfactant concentrations, temperature and centrifugation times) were evaluated and optimized. Under the optimized experimental conditions, the analytical characteristics of the method (e.g., limit of detection (LOD), linear range, preconcentration and improvement factors) were obtained. The proposed CPE method showed linear calibration within the range 5.0-200 ng mL(-1) of manganese(II) and the limit of detection of the method was 0.8 ng mL(-1) with an preconcentration factor of 50 when 25 mL of sample solution was preconcentrated to 0.5 mL. The relative standard deviation (RSD) and relative error were found to be 1.35% and 1.42%, respectively (C-Mn(II)= 150 ng mL(-1) = 6) for pure standard solutions. The interference effect of some cations and anions was also studied. In the presence of foreign ions, no significant interference was observed. The method was applied to the determination of manganese(II) in water and food samples with a recovery for the spiked samples in the range of 95.87-102.5%. (C) 2014 Elsevier B.V. All rights reserved.