Releasing and Chelating Agents

Chelating agents also are effective in certain cases. Ethylenediaminetetra-acetic acid (EDTA) forms strong chelates with alkaline earth elements and can be used to protect magnesium and calcium from reaction with phosphate, sulfate, selenium, boron, aluminum, and silicon. 8-Hydroxyquinoline has been used to protect magnesium and calcium from aluminum. 

Chemical treatment of a sample also may be used to control interferences. A number of techniques are available, including separation by precipitation, solvent-solvent extraction, and ion exchange techniques. For example, 8-hydroxyquinoline can be used to precipitate and separate a number of elements, such as manganese, copper, cobalt, nickel, and iron, from other major matrix elements. The test solution therefore has fewer extraneous elements present and fewer possibilities of interference exist. 

Some elements, such as copper, manganese, and iron, can be separated on an anion exchange resin as complex chloride anions and then removed by eluting with water. A less complex solution is therefore available for absorption spectral measurements. 

For other separation and concentration techniques the reader is referred to standard analytical separation texts and current publications in analytical chemical techniques. 

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