Factors Affecting Inorganic Solvent Extractions

Control of pH is critical to ensure conditions are favourable for the formation of the desired complexes. The extraction specificity needed influences the acceptable range of pH. Many inorganic extraction schemes use buffers. The lack of a buffer in an inorganic extraction should be viewed with suspicion, since the quantity of metal extracted is strongly pH dependent. In addition, chelating agents will alter the pH of the solution. Several buffers have been used for inorganic extractions for AAS determination, including borate, phosphate, citrate, acetate and formate. Acetate should not be used if lead or silver or other stable metal acetates are to be determined. Buffers can be a significant source of contamination, as can any unpurified reagent added to a sample.

The nature of the solvent is of special importance for inorganic extractions. There are several criteria which should be evaluated when choosing a solvent for an inorganic extraction. The solvent should have the following characteristics:

• Extracts the desired metal chelates

• Immiscible with aqueous solution (i.e. low solubility in water); for convenience, density > water if the sample is drawn off

• Does not form emulsions

• Compatible with the analytical determination technique

• Environmentally safe and nontoxic

• Available in an acceptably uncontaminated state.

In the case of flame AAS, ketones or esters are commonly used extraction solvents. The list of organic solvents used in inorganic extractions is extensive.

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Solar Panel Basics

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