Modified carbon nanotubes in online speciation of chromium in real water samples using hyphenated FI-FAAS

The aim of this study is to chemically modify multi-walled carbon nanotubes (MWCNTs) with L-arginine and then use them for speciation and preconcentration of chromium species. A flow injection (FI) system hyphenated to flame atomic absorption spectrometry (FAAS) was used for analysis of chromium species. The variables which influence the performance of a preconcentration system were optimized. The selectivity of modified MWCNTs towards chromium in the presence of matrix ions was also studied. Under the optimized conditions, the preconcentration factor and limit of detection achieved were 110 and 0.07 ng mL(-1), respectively. The precision of the reported method determined as the relative standard deviation was 1.0% for 100 mg L-1 Cr(III) solution. The concentration of Cr(VI) was determined after reducing it to Cr(III). The described method was successfully applied for chromium speciation in industrial and river water samples. The accuracy of the method was determined by analyzing Standard Reference Material 1640a (Trace Elements in Natural Water).