Ion-exchange chromatographic determination of anions by indirect photometric detection: comparison of eluent ions with respect to sensitivity enhancement

Abstract

Aromatic sulphonate and carboxylate eluent ions were examined for use in the sensitive determination of inorganic anions by indirect photometric ion chromatography. The naphthalene-1,3,6-trisulphonate ion was found to be the most sensitive for use as the eluent ion, the detection limit being as low as 1 × 10^–8 mol dm^–3. The naphthalene-1,5-disulphonate ion is recommended for the analysis of water samples containing anions at concentrations of between 1 × 10^–6 and 1 × 10^–5 mol dm^–3. These two eluent ions have several advantages over other choices: (i) detection is carried out at longer wavelengths (near 300 nm); (ii) the eluent ions are easily soluble in water and subsequently stable; (iii) their elution strength is not influenced by pH change; (iv) the eluent ions do not form any metal complexes; and (v) the reagents are inexpensive and commercially available.