A membrane-protected micro-solid-phase extraction method based on molecular imprinting and its application to the determination of local anesthetics in cosmetics.

As local anesthetics that are illegally added to cosmetics are harmful to consumer health, it is necessary to establish an efficient method for detecting these substances. Herein, a molecularly imprinted polymer (bupivacaine) was prepared by bulk polymerization and packed into a hollow fiber for use as an extraction phase to fabricate a membrane-protected micro-solid-phase extraction device. The optimal values of the influencing parameters for the microextraction process were as follows: a sample solution pH of 9.0, a loading and washing time of 2 h, and an elution time of 32 min. A gas chromatography-mass spectrometry method was established for the determination of local anesthetics and coupled with the microextraction method to successfully detect local anesthetics in cosmetic samples. The calibration curve for the proposed method was linear in the range of 0.4-50 mg/L and showed a good correlation coefficient (r2 ). The limits of detection for local anesthetics were in the range of 0.01-0.71 mg/L. The molecularly imprinted polymer exhibited good imprinting and selectivity, the micro-solid-phase extraction device was simple and inexpensive and fabrication was reproducible. The combination of molecular imprinting technology, membrane separation, and micro-solid-phase extraction methods used in this study can potentially be applied to pretreat local anesthetics in cosmetic samples.

In-situ preparation of porous monolithic polymer inside hollow fiber as a micro-solid phase extraction device for glucocorticoids in cosmetics.

Glucocorticoids have a certain whitening effect on the skin. However, frequent and long-term use of cosmetics including glucocorticoids is harmful to health. Herein, we proposed a novel micro-solid phase extraction method for the detection of prednisolone acetate, prednisone, and prednisolone in cosmetics coupled with high-performance liquid chromatography. In this method, porous monolithic polymer micro-extraction bars were prepared by "one-step, one-pot" in situ photopolymerization combined with sacrificial support in hollow fiber under water atmosphere. The crucial factors such as pH of sample solution, extraction, and elution times that influence micro-extraction were optimized and found to be 9.0, 2 h, and 32 min, respectively. Under the optimum experimental conditions, the linear range of the calibration curves were from 5.0 to 2000 µg/L with correlation coefficients (R2 ) between 0.9922 and 0.9996. The limit of detection and limit of quantification were 1.5 µg/L and 5.0 µg/L, respectively, and the recoveries were found to be in range of 69.0-113.3%. The analysis of precision for intraday and interday were less than 10.40 and 10.59%. The device has been successfully achieved photopolymerization under water atmosphere. The results indicated that this method is simple, accurate, and satisfactory for the pretreatment and determination of glucocorticoids in complex cosmetics samples.

A simple on-line detection system based on fiber-optic sensing for the realtime monitoring of fixed bed adsorption processes of molecularly imprinted polymers.

Fixed bed adsorption is widely used for separations and purifications of active components in medicine, and for wastewater treatment. At present, fixed bed adsorption breakthrough curve is generally obtained by manual sampling and off-line detection. In this study, we proposed a method for on-line monitoring of fixed bed adsorption process using a self-assembled fiber-optic sensing (FOS) system. The adsorption of 2,4-dichlorophenoxyacetic acid (2,4-D) on the fixed bed packed with molecularly imprinted polymers (MIPs) and non-imprinted polymers (NIPs) were studied. The reproducibility and precision of the system was investigated. The relative standard deviation (RSD) of the system was less than 1.54%, which indicates that the system has a good reproducibility. The effects of initial concentration, flow rate, adsorbent mass and particle size on the breakthrough curves were investigated. Through screening, it was found that adsorption kinetics of the polymer materials fit to Thomas and Yoon-Nelson models. The MIPs showed high binding capacity, good selectivity, fast adsorption rate, indicating a great potential for the treatment of 2,4-D contaminated water. Moreover, this study has identified that the detection method has the advantages of being on-line, realtime, simple, and accurate. The on-line method can facilitate the study of fixed bed adsorption processes and accelerate the understanding of adsorption kinetics.