Determination of Antimony Speciation in Cow Milk Using Dispersive Micro-solid Phase Extraction Based on Fibrous TiO2@g-C3N4Nanocomposites and ICP-MS After Sample Pretreatment by Artificial Gastric Juice

In this work, fibrous TiO2@g-C(3)N(4)nanocomposites (FTGCNCs) were used as a new adsorbent of dispersive micro-solid phase extraction for speciation of antimony in cow milk, including Sb(III), Sb(V), residual, digestible, and total Sb. Samples were prepared with artificial gastric juice to achieve bioaccessible species of elements before ICP-MS determination. Besides, adsorption behaviors of Sb(III) and Sb(V) on FTGCNCs were investigated. The results showed that Sb(III) was quantitatively adsorbed on FTGCNCs in the pH range of 2.0-4.0, while Sb(V) remained in aqueous phase. Sb(III) adsorbed on FTGCNCs was eluted completely with 1.5 mol L(-1)HNO(3)solution. The assay of Sb(V) was based on subtracting Sb(III) from total Sb. Total Sb was extracted and determined after the reduction of Sb(V) into Sb(III). The main parameters affecting the separation and determination of the analytes were examined in detail. Under optimal conditions, the limit of detection was 0.37 pg mL(-1)for Sb(III) with relative standard deviation of 4.1% (c = 1.0 ng mL(-1),n = 9). This method was successfully used for the analysis of Sb speciation in cow milk. To validate this method, a certified reference material of milk powder was analyzed, and the determined values were in good agreement with the certified values.