Soluble Membrane Separation Enrichment Methods

The application of solvent-soluble membrane in the determination of Cr (VI),I-,Pd (II),Pb (II) and Mo (VI) is described. It is found that the ions above react with certain complexant and surface active agent to produce the ternary complex,which can be collected by the membrane. So a simple and rapid preconcentration by solvent-soluble membrane and a subsequent spectrophotometric method is described for sensitive and selective determiantion of the ions above.At pH 5.0,hexabalent chromium,o-chlorophenylfluorone (o-Cl-PF) and tetradecylpyridinium chloride form the ternary ion-associte of chelate,which can be collected on a 0.2 y m-nitrocellulose membrane. The ion-associate and the filter are dissolved in a small volume of dimethyl sulfoxide (DMSO) acided with 0.15ml 3mol/L sulfuric acid,and the absorbance of the resulting solution is measured by means of spectrophotometric method at 545nm wavelength against the reagent blank and is proportional to the content of hexabalent chromium in the range of 0.1-1.8 ug in 5 ml solvent . The sensitivity of the ternary complex reaction is very high with molar absorptivity of 1.2 X105.The detection limits better than 0.3 ug/L can be achieved. The proposed method has been applied to the analysis of water samples from several sources,the recoveries of the hexavalent chromium added to the samples are quantitative,and results found are satisfactory.Based on oxidation of iodide to iodate and collection of ion-associate produced by tri-iodide with cation surfactant CTMAB,and a subsequent spectrophotometric method is described for sensitive and selective determination of the resulting solution owing to dissolving the membrane and analyte in an organic solvent. Absorbance due to the ion-associate in the solution is measured at 365 nm of maximum absorption wavelength against reagent blank. Beer's law is obeyed in the range 0.2-3.8ug I- in 5 ml of solvent or 75 ml of aqueous phase with good reproducibility and detection limit better than 1.3 ug dm-3 as I" can be achieved. The proposed method has been applied to the analysis of table salt,saline and water with quantitative recoveries andsatisfactory results.The complex of Pd (II) - NRS -Zeph,can be collected on nitrocellulose membrane. The complex and the filter are dissolved in 5 mL DMSO,and the absorbance of the resulting solution is measured by means of spectrophotometric method at 420nm wavelength against the reagent blank and is proportional to the content of Pd (II) in the range of 0.8-48ug in 5 ml solvent .The detection limits better than 0.2 ug/L can be achieved. The sensitivity of the ternary complex reaction is very high with molar absorptivity of 9.5 X104. The proposed method has been applied to the separation and determination of palladium (II) in catalyst and industrial waste water and results found are satisfactory.In the boron medium of pH=4.5,the complex of Mo (VI) - ARS-CPC,can be collected on nitrocellulose membrane. The complex and the filter are dissolved in a small volume of DMSO,and the absorbance of the resulting solution is measured by means of spectrophotometric method at 490 nm wavelength against the reagent blank.The detection limits better than 1.2ug/L can be achieved. In the boron medium of pH=9.0,the purple complex of Pb (II) - PAN,can be collected on nitrocellulose membrane. The complex and the filter are dissolved in a small volume of DMSO,and the absorbance of the resulting solution is measured by means of spectrophotometric method at 545nm wavelength against the reagent blank.The detection limits better than 1.0 u g/L can be achieved.