Um novo método seletivo foi desenvolvido para a separação e pré-concentração de íons Cd(II) tendo como base a formação de um complexo em uma mini-coluna contendo como suporte carvão ativado modificado com laranja de xilenol. Os íons Cd(II) pré-concentrados foram eluídos com 5,0 mL de solução 0,5 mol L-1 HNO 3 e determinados por espectrometria de absorção atômica com chama. Foram estudadas as condições de preparo do carvão ativado modificado, pH, vazões, bem como, o efeito de potenciais íons interferentes. Nas condições ótimas de trabalho, obteve-se um fator de pré-concentração de 200. O gráfico de calibração foi linear até 200 ng mL-1 de Cd(II) na solução inicial. O limite de detecção foi de 0,3 ng mL-1 Cd(II) e o desvio padrão relativo (RSD %) igual a 4,0% para uma solução 20,0 ng mL-1 Cd(II). O método foi aplicado com sucesso para determinar cádmio (II) em amostras de água e nos seguintes materiais de referência: lama de efluentes (CRM 144R) e água de mar (CASS 4). A new selective method was developed for the separation and preconcentration of Cd(II) ions based on its complex formation with Xylenol orange loaded on activated carbon as a solid support in a mini-column. The preconcentrated ions were eluted by passing 5.0 mL 0.5 mol L-1 HNO 3 solution through the solid support and then the Cd(II) contents was measured by flame atomic absorption spectrometry. Conditions for preparation of the modified activated carbon, pH and flow variables were studied, as well as, the effect of potential interfering ions. A preconcentration factor of 200 was achieved using the optimum conditions. The calibration graph was linear up to 200 ng mL-1 Cd(II) in the initial solution. The detection limit of the method was 0.3 ng mL-1 Cd(II) and the relative standard deviation (RSD%) was 4.0% for 20.0 ng mL-1 Cd(II). The method was successfully applied to the determination of cadmium(II) in water samples and in two reference materials: sewage sludge (CRM 144R), and sea water (CASS 4).
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