Simultaneous electrolytic deposition is proposed for minimization of Cu2+ and Pb2+ interferences on automated determination of Cd2+ 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) HNO3 + 0.1% (v/v) H2SO4 + 0.5 mol L-1 NaCl, Cu2+ is deposited as Cu on the cathode, Pb2+ is deposited as PbO2 on the anode while Cd2+ is kept in solution. With 60 s electrolysis time and 0.25 A current, Pb2+ and Cu2+ levels up to 50 and 250 mg L-1 respectively, can be tolerated without interference. With on-line extraction of Cd2+ 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).

A influência de digeridos e suspensões de açúcar no comportamento térmico de As usando Pd(NO3)2, Pd(NO3)2 + Mg(NO3)2, and Ni(NO3)2 como modificadores químicos foi investigada. Influência de 0,2%, 5%, 10% e 35% (v/v) HNO3 na calibração (1,00 - 10,0 µg As L-1) também foi feita. Um volume de 20 µL de amostra mais 5 µL Pd ou 5 µL Pd + 3 µL Mg, ou 20 µL Ni foi injetado no atomizador do GF AAS. Para cada modificador, temperaturas de pirólise e atomização foram avaliadas por meio de curvas de pirólise e de atomização, respectivamente. Para suspensão de açúcar, temperaturas de pirólise e atomização (Tp, Ta) obtidas foram: sem modificador (400° C, 2000° C); Pd (1400° C, 2200° C); Pd/Mg (1400° C, 2200° C) e Ni (1600° C, 2200° C). Os valores para digeridos de açúcar foram: sem modificador (400° C, 2200° C); Pd (1400° C, 2200° C); Pd/Mg (1400° C, 2200° C) e Ni (600° C, 2200° C). Paládio foi selecionado como o melhor modificador químico. O tempo de vida do tubo de grafte foi de aproximadamente 350 queimas, o RSD (n = 12) para uma amostra típica contendo 5,52 µg As L-1 foi < 2,2% e o limite de detecção foi 2,4 pg As. Recuperações entre 80 e 92% foram encontradas.

The influence of digests and slurries of sugar on thermal behavior of As using Pd(NO3)2, Pd(NO3)2 + Mg(NO3)2, and Ni(NO3)2 as chemical modifiers was investigated. Influence of 0.2%, 5%, 10% and 35% (v/v) HNO3 on calibration (1.00 - 10.0 µg As L-1) was also done. A volume of 20 µL sample plus 5 µL Pd or 5 µL Pd + 3 µL Mg, or 20 µL Ni was injected into the atomizer of GF AAS. For each modifier, the pyrolysis and atomization temperatures were evaluated by means of pyrolysis and atomization curves, respectively. For sugar slurries, pyrolysis and atomization temperatures (Tp, Ta) found were: without modifier (400° C, 2000° C); Pd (1400° C, 2200° C); Pd/Mg (1400° C, 2200° C) and Ni (1600° C, 2200° C). The values for sugar digests were: without modifier (400° C, 2200° C); Pd (1400° C, 2200° C); Pd/Mg (1400° C, 2200° C) and Ni (600° C, 2200° C). Palladium was selected as the optimum chemical modifier. The lifetime of the graphite tube was ca. 350 firings, the RSD (n=12) for a typical 5.52 µg As L-1 sample was < 2.2% and the detection limit was 2.4 pg As. Recoveries between 80 and 92% of spiked samples were found.

Este trabalho descreve uma revisão a respeito do emprego da técnica de espectrometria de absorção atômica simultânea em forno de grafite (SIMAAS) em determinações multielementares de elementos-traço em diferentes matrizes. Os principais parâmetros envolvidos e que devem ser considerados em medidas multielementares, tais como, fonte de radiação, geometria do forno, programa de aquecimento e natureza e quantidade de modificador químico, são descritos.

A review on the use of graphite furnace atomic absorption spectrometry for simultaneous multielement determination of metals at trace levels in different samples is described. The main parameters to be considered in multi-element analysis such as light sources, kind of graphite furnace tubes, time and temperature program, and composition and amount of modifier are summarized and discussed.