Application of Dowex-2 loaded with sulfonephthalein dyes to the preconcentration of copper(II) and cadmium(II)

Abstract

Dowex-2 loaded with sulfonephthalein dyes, viz., Pyrocatechol Violet (PV) and Xylenol Orange (XO), was prepared and investigated for the preconcentration of Cu^II and Cd^II prior to their determination by flame atomic absorption spectrometry. At pH 7.0–8.0, 1 g of the resin sorbs 23–26 mg of PV or XO. Copper(II)( 0.01 ppm) is sorbed quantitatively at pH 5.0–10.0 and 6.0–10.0 by the PV- and XO-loaded resin, respectively. The corresponding pH ranges for maximum sorption of Cd^II( 0.01 ppm) are 9.5–10.0 and 8.0–10.0. Copper and Cd were desorbed quantitatively with 1 mol dm^–3 HCl and 1 mol dm^–3 HNO₃, respectively. The metal ion sorbing capacity of the two resins was found to be ⩽ 100 µg of metal per 100 mg of resin. The sorption decreases when the concentration of NaCl exceeds 0.1 mol dm^–3. The applicability of both resins to the preconcentration of Cu and Cd prior to their determination by flame atomic absorption spectrometry was demonstrated by analysing Yamuna river water samples for the two ions (relative standard deviation = 4.8–5.7%).