Solid-phase extraction with multiwalled carbon nanotubes prior to photochemical generation of cadmium coupled to high-resolution continuum source atomic absorption spectrometry

Abstract

Multiwalled carbon nanotubes (MWCNTs) were used as sorbent for solid phase extraction (SPE) of cadmium ions from water samples. After extraction, volatile cadmium species were generated in the presence of propionic acid under ultraviolet radiation (photochemical generation, UV CVG) and determined by high-resolution continuum source atomic absorption spectrometry (HR-CS AAS) with quartz tube atomization (QTA). The experimental parameters including pH of the solutions, amount of MWCNTs, flow rate of sample, eluent concentration, maximum sample volume and coexisting ions, as well as main parameters of UV CVG HR-CS QTA AAS were investigated. The effective preconcentration of trace cadmium was achieved in pH 7 and the retained cadmium was efficiently eluted with 0.5 mol L⁻¹ HNO₃. The limit of detection was 25 μg L⁻¹ and the achieved preconcentration factor was 8.8. The relative standard deviation (RSDs) was 15%. The accuracy of this method was validated by the analyses of NIST SRM 1643e (trace elements in water) and ERM-CA011b (hard drinking water) certified reference materials. The element contents measured in these reference materials were in satisfactory agreement with the certified values according to the t-test for a 95% confidence level. The presented method was successfully applied for the determination of cadmium in four different water samples (seawater, lake water, mine water and tap water).