alumina/graphene oxide nanocomposite as a new sorbent for extraction and preconcentration of three preservatives by dispersive solid phase extraction method

Recently, the development of new sorbent materials employed for solid phase extraction has received more attraction due to the need of improving the adsorption efficiency and selectivity [1]. among different adsorbents, nanomaterials have attracted great interest because of their unusual mechanical, optical properties and high surface area. graphene-based materials have been used as spe sorbents for various pollutants because of their large surface area, high adsorption capacity for organic pollutants, and chemical and thermal stability [2]. the esters of p-hydroxybenzoic acid, commonly known as parabens, are worldwide applied as preservatives in a large number of personal care products and canned foods due to their antimicrobial and antifungal properties [3]. considering the complexity of matrix and low concentration of parabens in real samples, a sample preparation step is required for isolation or enrichment of the analytes prior to the final analysis [4]. in the present study, a new nanosorbent, alumina-graphene oxide nanocomposite, has been successfully synthesized. the synthesized material was characterized by ft-ir spectroscopy, thermal gravimetric analysis (tga), scanning electron microscopy (sem) and energy-dispersive x-ray (edx) analysis. in the next step, the synthesized material was used as sorbent for solid-phase extraction of trace amounts of three preservatives (parabens) and followed by determination using hplc/uv. several variables affecting the extraction efficiency of the analytes i.e., amount of sorbent, salt concentration, extraction time, and desorption conditions were investigated and optimized by experimental design and one-at-a time methodologies. under the optimum conditions, the analytical performance of the method showed good linear dynamic ranges (0.2-100 μg l-1) and good limits of detection (0.03-0.05 μg l-1), and the relative standard deviations (rsd%) were less than 4.4% (n = 5). preconcentration factors of the target analytes were obtained in the range of 128-173. finally, the applicability of the proposed method was evaluated by extraction of the parabens from some real samples including wastewater, cream, toothpaste, and juice samples, with recoveries from 88 to 109%, and relative standard deviations (rsds%) less than 8.7 % (n = 3).