Comparative Insight into the Performance of Two Different Amine-Functionalized CNTs for the Chemical Speciation of Chromium

Persistent industrial activities have led to an increase in the chromium content in environmental water bodies. The accurate quantification of trace chromium species such as Cr(III) and Cr(VI) is crucial as Cr(VI) can exhibit toxicity even at sub-ppb levels. We report herein a comparative chromium speciation study using two chemically functionalized nanoadsorbents and determination with hyphenated flow injection-flame atomic absorption spectrometry (FI-FAAS). The most efficient preconcentration performance was obtained by optimizing the chemical and hydrodynamic parameters. Cr(VI) concentration was ascertained by the reduction to Cr(III) as the nanoadsorbents were selective for Cr(III) adsorption only; thus, speciation was achieved. The method was selective for Cr(III) in the presence of interfering matrix components. Preconcentration factor >90 and detection limit <0.11 mu g L(-1)were obtained for both the nanoadsorbents (%RSD similar to 1.0 %). The adsorption capacity of CNT-TYR and CNT-ASA was found to be 42.0 and 43.2 mg g(-1), respectively. The application of the proposed method to contaminated water samples gave recoveries >95 %. The accuracy of the method was verified using NIST SRM 1640a.