Combination of solid phase extraction and flame atomic absorption spectrometry for trace analysis of cadmium

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 HNO3 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).