Minimization of lead and copper interferences on spectrophotometric determination of cadmium using electrolytic deposition and ion-exchange in multi-commutation flow system

• Published in: Talanta (Oxford) Vol. 53; no. 3; pp. 497 - 503
• Main Authors: Gomes Neto, José A, Oliveira, Adriana P, Freshi, Gian P.G, Dakuzaku, Carolina S, de Moraes, Mercedes
• Format: Journal Article
• Language: English
• Published: Amsterdam Elsevier B.V 04.12.2000; Oxford Elsevier
• Subjects: Analytical chemistry; Cadmium; Chemistry; Electrolytic deposition; Exact sciences and technology; Flow analysis; Malachite green; Solid phase extraction; Spectrometric and optical methods; Spectrophotometry; Cadmium; Solid phase extraction; Electrolytic deposition; Spectrophotometry; Flow analysis; Malachite green; Water; Interelement effect; Triarylmethane dye; Basic dye; Chemical enrichment; Absorption spectrometry; Accuracy; Electrolysis; Detection limit; Reference material; Lead; Copper; Ion exchange; Vegetable
• ISSN: 0039-9140; 1873-3573
• DOI: 10.1016/S0039-9140(00)00516-6

A new strategy for minimization of Cu 2+ and Pb 2+ interferences on the spectrophotometric determination of Cd 2+ by the Malachite green (MG)–iodide reaction using electrolytic deposition of interfering species and solid phase extraction of Cd 2+ in flow system is proposed. The electrolytic cell comprises two coiled Pt electrodes concentrically assembled. When the sample solution is electrolyzed in a mixed solution containing 5% (v/v) HNO 3, 0.1% (v/v) H 2SO 4 and 0.5 M NaCl, Cu 2+ is deposited as Cu on the cathode, Pb 2+ is deposited as PbO 2 on the anode while Cd 2+ is kept in solution. After electrolysis, the remaining solution passes through an AG1-X8 resin (chloride form) packed minicolumn in which Cd 2+ is extracted as CdCl 4 2−. Electrolyte compositions, flow rates, timing, applied current, and electrolysis time was investigated. With 60 s electrolysis time, 0.25 A applied current, Pb 2+ and Cu 2+ levels up to 50 and 250 mg l −1, respectively, can be tolerated without interference. For 90 s resin loading time, a linear relationship between absorbance and analyte concentration in the 5.00–50.0 μg Cd l −1 range ( r 2=0.9996) is obtained. A throughput of 20 samples per h is achieved, corresponding to about 0.7 mg MG and 500 mg KI and 5 ml sample consumed per determination. The detection limit is 0.23 μg Cd l −1. The accuracy was checked for cadmium determination in standard reference materials, vegetables and tap water. Results were in agreement with certified values of standard reference materials and with those obtained by graphite furnace atomic absorption spectrometry at 95% confidence level. The R.S.D. for plant digests and water containing 13.0 μg Cd l −1 was 3.85% ( n=12). The recoveries of analyte spikes added to the water and vegetable samples ranged from 94 to 104%.