Spiral stir bar sorptive extraction with polyaniline-polydimethylsiloxane sol-gel packings for the analysis of trace estrogens in environmental water and animal-derived food samples.

A spiral stir bar was proposed by using stainless steel spring as the extraction phase carrier to avoid the extraction phase friction and increase the amount of extraction phase for improving extraction efficiency. The extraction phase is filled in the cavity of the spring, resulting in a larger amount of the extraction phase than that conventionally coated on glass stir bar or stainless steel wire. Polyaniline-polydimethylsiloxane sol-gel packed spiral stir bar was prepared and evaluated for the extraction of five estrogens. The prepared spiral stir bar presented good extraction efficiency/preparation reproducibility and long lifetime (more than 150 reused times) for target estrogens. Based on it, a method of spiral stir bar sorptive extraction combined with high performance liquid chromatography coupled with ultra-violet detection was developed for the analysis of trace estrogens in environmental and food samples. The detection limit for five estrogens was 0.11-.31 µg/L, with the enrichment factors of 83.0-118-fold (maximal enrichment factor: 200-fold). The reproducibility evaluated with each estrogen of 5 µg/L (n = 5) was 5.8-8.9%. The method was successfully applied for the determination of estrogens in environmental water and animal-derived food samples.

Water-compatible graphene oxide/molecularly imprinted polymer coated stir bar sorptive extraction of propranolol from urine samples followed by high performance liquid chromatography-ultraviolet detection.

Due to the high selectivity and stability, molecularly imprinted polymers (MIPs) have been successfully applied in stir bar sorptive extraction (SBSE) as a special coating to improve the selective extraction capability for target analytes. However, traditional MIPs usually suffer from incompatibility in aqueous media and low adsorption capacity, which limit the application of MIP coated stir bar in aqueous samples. To solve these problems, a water-compatible graphene oxides (GO)/MIP composite coated stir bar was prepared in this work by in situ polymerization. The prepared water-compatible GO/MIP coated stir bar presented good mechanical strength and chemical stability, and its recognition ability in aqueous samples was improved due to the polymerization of MIP in water environment, the adsorption capacity for target analytes was also increased by the addition of GO in MIP pre-polymer solution. Based on it, a method of water-compatible GO/MIP coated stir bar sorptive extraction combined with high performance liquid chromatography-ultraviolet detector (HPLV-UV) was proposed for the analysis of propranolol (PRO) in aqueous solution. The influencing factors of SBSE, such as sample pH, salt effect, stirring rate, extraction time, desorption solvent and desorption time, were optimized, and the analytical performance of the developed SBSE-HPLC-UV method was evaluated under the optimized conditions. The limit of detection (LOD) of the proposed method for PRO was about 0.37 µg L(-1), and the enrichment factor (EF) was 59.7-fold (theoretical EF was 100-fold). The reproducibility was also investigated at concentrations of 5 µg L(-1) and the relative standard deviation (RSD) was found to be 7.3% (n=7). The proposed method of GO/MIP coating-SBSE-HPLC-UV was successfully applied for the assay of the interested PRO drug in urine samples, and further extended to the investigation of the excretion of the drugs by monitoring the variation of the concentration of PRO in urine within 10h after drug-taking.