Determination of diethylstilbestrol in milk using carbon nanotube-reinforced hollow fiber solid-phase microextraction combined with high-performance liquid chromatography

Carbon nanotube-reinforced hollow fiber solid-phase microextraction (CNTs-HF-SPME) combined with high-performance liquid chromatography (HPLC) was used to extract and determine diethylstilbestrol (DES) in milk products. Wall pores of the hollow fiber were filled with multi-walled carbon nanotubes (MWCNTs) using sol–gel technology. In the proposed method, DES was selectively extracted by MWCNTs, desorbed to methanol, and analyzed by HPLC. The parameters affecting the efficiency of CNTs-HFSPME, such as the length of the hollow fiber, extraction and desorption times, extraction temperature, stirring rate, pH of the sample solution, and the amount of organic solvent and salt in the sample solution, were investigated and optimized. Under the optimized extraction conditions, the method showed good linearity (24–960 μg L−1), a low method detection limit (MDL, 5.1 μg L−1), and good recoveries at four different concentrations. It was proven to be simple, rapid, sensitive, and solvent free for the analysis of DES in dairy products.