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Deposição eletrolítica catódica e anódica simultâneas para minimizar interferências de cobre e chumbo na determinação espectrofotométrica de cádmio em água e alimentos via reação com Verde de Malaquita e iodeto

2001; Brazilian Chemical Society; Volume: 24; Issue: 6 Linguagem: Inglês

10.1590/s0100-40422001000600006

1678-7064

Adriana Paiva de Oliveira, Gian Paulo Giovanni Freschi, Carolina Sinabucro Dakuzaku, Mercedes de Moraes, Marisa Spirandeli Crespi, José Anchieta Gomes Neto,

Analytical chemistry methods development

MALACHITE GREEN-IODIDE REACTION.Simultaneous electrolytic deposition is proposed for minimization of Cu 2+ and Pb 2+ interferences on automated determination of Cd 2+ by the Malachite Green-iodide reaction.During electrolysis of sample in a cell with two Pt electrodes and a medium adjusted to 5% (v/v) HNO 3 + 0.1% (v/v) H 2 SO 4 + 0.5 mol L -1 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.With 60 s electrolysis time and 0.25 A current, Pb 2+ and Cu 2+ levels up to 50 and 250 mg L -1 respectively, can be tolerated without interference.With on-line extraction of Cd 2+ in anionic resin minicolumn, calibration graph in the 5.00 -50.0 µg Cd L -1 range is obtained, corresponding to twenty measurements per hour, 0.7 mg Malachite Green and 500 mg KI and 5 mL sample consumed per determination.Results of the determination of Cd in certified reference materials, vegetables and tap water were in agreement with certified values and with those obtained by GFAAS at 95% confidence level.The detection limit is 0.23 µg Cd L -1 and the RSD for typical samples containing 13.0 µg Cd L -1 was 3.85 % (n= 12).