Selective speciation of inorganic arsenic in water using nanocomposite based solid-phase extraction followed by inductively coupled plasma-mass spectrometry detection

The multi-walled carbon nanotubes-branched polyethyleneimine (MWCNTs-BPEI) adsorbent composite material was employed to separate and pre-concentrate As(V) in water samples. The characterization of MWCNTs-BPEI by X-ray diffraction (XRD), thermogravimetric analysis (TGA), Fourier transform infrared (FTIR) spectroscopy and Raman spectroscopy showed successful modification of the composite. The MWCNTs-BPEI composite exhibited selective retention of As(V) in the presence of As(III) in water samples of pH 7 using 40 mg of composite as adsorbent. The pre-concentrated As(V) was quantified using inductively coupled plasma-mass spectrometry (ICP-MS). A limit of detection (LOD) of 0.0537 µg L⁻¹ and limit of quantification (LOQ) of 0.179 µg L⁻¹ were achieved along with pre-concentration factor of 23.3. A percentage recovery of 81.0% confirm the accuracy of the method. The As(V) concentrations in water were in the range of 0.0612–3.65 µg L⁻¹. The As(V) concentrations determined using solid-phase extraction (SPE) procedure were in good agreement with the concentrations obtained using high performance liquid chromatography hyphenated to inductively coupled mass-mass spectrometry (HPLC hyphenated to ICP-MS).