Eluent sulfosalicylic acid

Ding, M., Tanaka, K., Hu, W., Haddad, P. R., and Miyanaga, A. (2001) Simultaneous Determination of Anions and Cations in Environmental Samples by Using a Weakly Acidic Cation-exchange Column with 2, 6-pyridinedicarboxylic Acid, Sulfosalicylic acid, and 18-crown-6 as Eluent, J. Liq. Chromatogr. Rel. Techn. 24, 3105-3117. 

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]. 

Tartaric acid and sulfosalicylic acid eluents, which are acids of low pK, were suitable for rapid separation of strong-acid anions and of cations, but the high background conductivity level gave poor detector response for weak-acid anions. When propionic acid (pK = 4.66) was used as the eluent, resolution of weak-acid anions was improved, but retention times for and Mg were very long. With a succinic acid eluent (pK = 4.00), all analyte ions were well resolved, as shown in... 

A mobile phase containing sulfosalicylic acid or succinic acid seems to work very well. The mobile phase is acidic enough to repress ionization of weakly acidic analytes but the background conductivity is reasonably low. Some of the organic acid in the eluent is adsorbed by the resin, and this leads to improved peak shape. The only downside of this eluent is that a system peak appears later in the chromatogram that may partially coincide with an analyte peak. The system peak stems from partial desorption of the sulfosalicylic or succinic acid when an aqueous sample is injected. 

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