Green chemicals-assisted dispersive magnetic solid-phase extraction: a prospect for speciation of Cr (III)/Cr (VI) in environmental water samples

In this research, hydrophobic task-specific room temperature ionic liquid (HTSRTIL) as a green modifier was synthesised and electrostatically in-situ immobilised on the magnetic multi-wall carbon nanotube (MMWCNT). This green reusable nano sorbent was employed successfully for the speciation/extraction of chromium species. The adsorbent was characterised by scanning electron microscopy (SEM), X-ray diffraction (XRD), vibrating sample magnetometer (VSM), Energy dispersive x-ray spectrometry (EDS), and Fourier transform infrared spectrophotometer (FT-IR). The methodology was based on the dispersive magnetic solid-phase extraction (DMSPE) decorated with HTRTIL as a chelating agent for speciation of chromium. Total chromium was specified by oxidising Cr (III) to Cr (VI) using KMnO(4)in acid media. The concentration of Cr (III) was obtained by the difference of total chromium and Cr (VI). The target ion was adsorbed on the surface of the synthesised extractant and easily separated by an external magnet. The eluted analyte is being finally measured by the UV-Vis spectrophotometer. The effect of various parameters (including pH, sample volume, adsorbent amount, extraction time, and type and volume of the eluent) has been considered in depth in the optimisation process. The developed procedure, which has been analytically characterised under its optimal operation conditions, allows good linearity between 1-200 mu g L(-1)and detection limits of 0.4 mu g L-1. The precision of the method expressed as the relative standard deviation (RSD) 4.9% (n = 5) (intra-day) and 5.3% (inter-day) while the enrichment factor is 300. The proposed method has been used for the speciation of chromium from water (river, well, spring, and tap) with the recoveries in the range from 79 to 99%.

Automated summary

In this research, a hydrophobic task-specific room temperature ionic liquid was synthesized and immobilized on magnetic multi-wall carbon nanotubes to create a reusable nano sorbent for the extraction and speciation of chromium species. The methodology involved adsorption of the target ion on the surface of the extractant, separation using an external magnet, and measurement by UV-Vis spectrophotometer. The developed procedure showed good linearity, low detection limits, and high precision.