In this study, a new method for the preconcentration of cadmium ions using modified aquatic macrophytes - Salvinia molesta as biosorbent in an on-line preconcentration system coupled to flame atomic absorption spectrometry (FAAS) was developed. The method is based on preconcentration of 20.0 mL sample at pH 3.75 through 35.0 mg of biosorbent at 10.0 mL min-1 and subsequent elution with 0.5 mol L-1 HNO3. A preconcentration factor of 31-fold, linear dynamic range from 5.0 to 70.0 µg L-1 (r = 0.9996) and detection and quantification limits of 0.15 and 0.51 µg L-1 were obtained. The characterization of the biosorbent chemically modified with NaOH and citric acid, was performed through FTIR and SEM measurements. The method precision was found to be 3.97 % and 1.48 % for 5.0 and 60.0 µg L-1 Cd(II) solutions, respectively. The applicability of method was checked by analysis of different kind of water samples and certified reference material.
Keywords: Atomic spectrometry; Biosorption; Flow injection analysis and water.