Selective cloud point extraction and graphite furnace atomic absorption spectrometric determination of molybdenum (VI) ion in seawater samples

Latest approaches on green chemistry preconcentration methods for trace metal determination in seawater--a review

Evaluation of trace metal levels in seawater samples is undertaken regularly by research groups all over the world, leading to a growing demand for techniques involving fewer toxic reagents, less time-consuming protocols and lower limits of detection. This review focuses on providing a brief but concise description of the latest methodologies developed to this end, outlining the advantages and disadvantages of the various protocols, chelating and dispersive agents and instruments used. Conclusions are drawn on the basis of the articles reviewed, highlighting improvements introduced in order to enhance the performance of the protocols.

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 528nm. 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 5.0-200ngmL(-1) of manganese(II) and the limit of detection of the method was 0.8ngmL(-1) with an preconcentration factor of ∼50 when 25mL of sample solution was preconcentrated to 0.5mL. The relative standard deviation (RSD) and relative error were found to be 1.35% and 1.42%, respectively (CMn(II)=150ngmL(-1), n=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%.

Ali AA, Hassanien MM. Cloud point extraction of Pd(II), Au(III), and Ag(I) prior to their determination by graphite furnace atomic absorption spectrometry

A simple and rapid cloud point extraction methodology has been developed for the separation and preconcentration of palladium (Pd2+), gold (Au3+), and silver (Ag+) ions. The metal ions in the initial aqueous solution were complexed with 4-allylthiosemicarbazide, and Triton X-114 was added as surfactant. Dilution of the surfactant-rich phase with acidified metanol was performed after phase separation, and the metal ions were determined by graphite furnace atomic absorption spectrometry. The main factors affecting the cloud point extraction procedure, such as pH, concentration of the ligand, amount of Triton X-114, equilibrium temperature, and incubation time, were investigated and optimized. Under the optimum experimental, the calibration graphs were linear upto 100 μg L−1 for Pd2+ and Au3+ and up to 80 μg L−1 for Ag+. The enrichment factors were 48, 53, and 51 for Pd2+, Au3+, and Ag+, respectively. The limits of detection, based on three times the standard deviation of the blank signal by seven replicate measurements, were 0.15, 0.07, and 0.04 μg L−1 for Pd2+, Au3+, and Ag+, respectively. The accuracy of the results was verified by analyzing spiked real samples (water, blood, and urine) as well as by comparison the results of geological samples with those obtained by ICP−MS after solvent extraction using ammonium pyrrolidinedithiocarbamate in methyl isobutyl ketone. The proposed method has been applied for the determination of the metal ions in real samples with satisfactory results.

Complex-forming organic ligands in cloud-point extraction of metal ions: a review

Cloud-point extraction (CPE), an easy, safe, environmentally friendly, rapid and inexpensive methodology for preconcentration and separation of trace metals from aqueous solutions has recently become an attractive area of research and an alternative to liquid-liquid extraction. Moreover, it provides results comparable to those obtained with other separation techniques and has a greater potential to be explored in improving detection limits and other analytical characteristics over other methods. A few reviews have been published covering different aspects of the CPE procedure and its relevant applications, such as the phenomenon of clouding, the application in the extraction of trace inorganic and organic materials, as well as pesticides and protein substrates from different sources, or incorporation of CPE into an FIA system. This review focuses on general properties of the most frequently used organic ligands in cloud-point extraction and on literature data (from 2000 to 2012) concerning the use of modern techniques in determination of metal ions' content in various materials. The article is divided according to the class of organic ligands to be used in CPE.