Organic Extraction of Metals

The undissociated chelating agent also is distributed between the organic and aqueous phases  

This ratio should be as large as possible to maximize the efficiency of the extraction. 

Assuming that [M+n] [MA ]aq and substituting from the equations above for K, K2, and AV the following is obtained  

If the amount of chelating agent in the organic phase is fixed, then 

The most common chelating agents used to extract metals from water samples are ammonia pyrolidine dithiocarbamate (APDC) and 8-hydroxyquinone. Methyl isobutyl ketone (MIBK) is generally used as a solvent. In a typical extraction, 1 mL of APDC is added to 50 to 100 mL of aqueous sample in a volumetric flask. The pH of the aqueous sample is adjusted for maximum extraction of the analyte of interest. Then 10 mL of MIBK is added (the volumetric ratio of sample to MIBK is usually less than 40) and the mixture is vigorously shaken for 30 seconds. The metal chelate partitions into the organic phase, which floats on the water. More water can be added to raise the organic level into the neck of the flask so that it can be 

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