Use of fibrous TiO2@graphitic carbon nitride nanocomposites in dispersive micro-solid phase extraction for arsenic species before inductively coupled plasma mass spectrometry determination

In this study, fibrous TiO2@graphitic carbon nitride nanocomposites (FTGCNCs) were used as a new adsorbent for dispersive micro-solid phase extraction of arsenic speciation, including As(III), As(V), total, suspended, soluble, organic and inorganic As, followed by ICP-MS determination. The in-situ formation of g-C3N4 on the surface of TiO2 nanofibers (TDNFs) greatly reduces the aggregation of graphitic carbon nitride (g-C3N4) to increase its specific surface area. In addition, TDNFs provide hydrophilicity with the relative hydrophobic surface of g-C3N4 to enhance its dispersibility in polar media and affinity for polar compounds. Furthermore, adsorption behaviors of As(III) and As(V) on FTGCNCs were studied. The experimental results showed that As(V) was quantitatively adsorbed on FTGCNCs in the pH range of 2.0-4.0, while As(III) remained in aqueous phase. As(V) retained on FTGCNCs was eluted completely with 1.0 mol L-1 HNO3 solution. The assay of As(III) was based on subtracting As(V) from total As. Total As was extracted and determined after the oxidation of As(III) into As(V). The main parameters affecting the separation and determination of the analytes were examined in detail. Under optimal conditions, the limits of detection were 1.2 pg mL(-1) and 0.6 pg mL(-1) for As(IIII) and As (V) with relative standard deviations of 6.1% and 5.7% (c = 0.1 ng mL(-1), n = 9), respectively. This method was successfully utilized for the analysis of As speciation in natural water samples. To verify this method, a certified reference material was analyzed and the determined values were in good agreement with the certified values.