Metal extraction factors determining effectiveness

A simple method was described for the extraction and determination of ultratrace amounts of Cu(II) ions using octadecyl-bonded sihca membrane disks modified with a recently synthesized SchifPs base 2,2 -[l,2-ethane-diyl-hir-(nitriloethyhdyne)]-hir-(l-naphthalene). The pH effect, nature and amount of counter anions, flow rates, and type of stripping acid were evaluated as the important factors of extraction efficiency of metal ions. The capacity was found to be 396 p.g of copper for the membrane disks modified by 5 mg of the hgand. The limit of detection of the proposed method is 4 ng/lOOO ml. The structure of the organic modifier is given in Scheme 8. 

Gardner and Yates [26] developed a method for the determination of total dissolved cadmium and lead in estuarine waters. Factors leading to the choice of a method employing extraction by chelating resin, and analysis by carbon furnace atomic absorption spectrometry, are described. To ensure complete extraction of trace metals, inert complexes with humic-like material are decomposed by ozone [27]. The effect of pH on extraction by and elution from chelating resin is discussed, and details of the method were presented. These workers found that at pH 7 only 1-2 minutes treatment with ozone was needed to completely destroy complexing agents such as EDTA and humic acid in the samples. 

When major components of plating solutions are determined, large dilutions may be required (e.g. a factor of 5000) to bring the sample into the normal working range for flame analysis. Such dilutions will, however, minimise any interference effects and viscosity effects from additives, and are thus to be preferred to the use of less sensitive lines or burner rotation. The above interference effects may be important in the determination of trace metal levels and attempts should be made to match the standards for major component levels, or to use the method of standard additions. Solvent extraction to remove the analyte from the matrix may be necessary. 

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