Sulfosalicylic Acid as a Masking Agent

The successful application of 5-sulfosalicylic acid in ion exchange separations was demonstrated by Fritz and Palmer [15]. At an appropriate pH, they found that alumi-num(III), iron(III), uranium(VI), and vanadium(IV) are complexed and pass quickly through a cation exchange column. A number of other cations, including the rare earths, are not complexed and are retained on the column. Their application was simply a group separation, and no chromatographic separation of individual metal ions was involved. 

Efficient and selective cation chromatographic separations are possible with an ethylenediammonium tartrate eluent at pH 4.5 and sulfosalicylic acid added to the sample before injection. At pH 4.5 zinc(Il) can be chromatographed without interference from a 20-fold excess of thorium(IV), vanadium(IV), or uranium(Vl), or from a 100-fold excess of iron(lll) when sulfosalicylic acid is added to the sample [14]. 

Analysis of rare earth cations using sulfosalicylic acid to mask a large excess of alu-minum(lll) also proved quite successful. Linear calibration curves were obtained over at least 0.0.5 to 0.50 mM rare earth with 2.0 mM aluminum and 10 mM sulfosalicylic acid at pH 4.5. 

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