Application of polyurethane foam loaded with BTAC in an on-line preconcentration system: cadmium determination by FAAS

In the present paper, the use of polyurethane foam modified by 2-(2-benzothiazolylazo)-2-p-cresol (BTAC) as a sorbent in an on-line preconcentration system to determine cadmium trace levels by FAAS is proposed. The procedure was based on the chemical sorption of cadmium (II) ions onto a minicolumn packed with polyurethane foam, followed by 0.10 mol l(-1) hydrochloric acid elution and direct determination by Flame Atomic Absorption Spectrometry. The flow system was operated in a time-based mode. Chemical and flow variables were studied. Results demonstrated that sample solutions containing cadmium(II) in the range of concentration from 0.91 to 30.00 mu g l(-1), pH between 6.50 and 9.25 could be determinated by this procedure, in a preconcentration time of 1 min. Flow rates in preconcentration and elution steps were 7.00 and 4.00 ml min(-1), respectively. The precision of the preconcentration procedure (evaluated as standard deviation of solutions containing 1.0-30.0 mu g l(-1) of cadmium) varied in the range from 5 to 1%. The preconcentration factor, calculated as the ratio of the linear section of the slopes of the analytical curves before and after preconcentration, was 41, for a volume sample of 7.00 ml. The detection limit was 0.27 mu g l(-1) for a preconcentration time of 1 min. The proposed procedure was applied for determination of cadmium in biological reference materials. Achieved results demonstrated that the procedure can be applied for analysis of biological materials with satisfactory accuracy. (C) 2000 Elsevier Science B.V. All rights reserved.