A molecularly imprinted polymer based monolith pipette tip for solid-phase extraction of 2,4-dichlorophenoxyacetic acid in an aqueous sample.

This paper presents a simple approach for fabrication of a pipette tip solid-phase extraction (PT-SPE) device, which possesses a monolith structure with low back pressure and has high selectivity to 2,4-dichlorophenoxyacetic acid (2,4-D). Pipette tips were packed with molecularly imprinted polymers (MIPs) as a selective adsorbent and high-density polyethylene (HDPE) as a co-sintering agent, and then heated to form a monolith extraction device. The key factors including the particle size and amount of packing material, and the type and volume of elution solvent, which influence PT-SPE device performance were optimized. A packing material of 40 mg/0.20 mL in a ratio of 4/6 (MIPs/HDPE) and treatment temperature of 150 °C was selected. By the determination with high-performance liquid chromatography (HPLC-SPD), the extraction device was found to have a good extraction recovery for a 2,4-D lake water sample at a low concentration (0.006 mg L-1) with an enrichment factor about 50. The proposed method provided a simple approach for the fabrication of a PT-SPE monolith device with reduced back pressure and wall effect, which are very important for improving the extraction efficiency. And the device will have promising application in the extraction of a variety of analytes in complex 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.

Membrane-Protected Molecularly Imprinted Polymer for the Microextraction of Indole-3-butyric Acid in Mung Bean Sprouts.

Based on the hollow fiber protected molecularly imprinted polymer, a micro-solid-phase extraction (µ-SPE) method was developed and applied for the analysis of indole-3-butyric acid in mung bean sprouts by high-performance liquid chromatography. The extraction conditions of the µ-SPE method were optimized using L9(34) orthogonal, and optimum conditions were found as follows: pH of sample solution was 2.0, chloroform was the organic solvent for embedding the µ-SPE bars, and acetonitrile was the desorption solvent. In addition, the extraction time was 80 min, desorption time was 5 min, stirring speed was 800 rpm, and concentration of NaCl was 10%. Under the optimum conditions, a standard curve was established for IBA, with a correlation coefficient of 0.9999. After extraction with phosphate buffer solution (pH = 9.0), successful pretreatment of mung bean sprouts was achieved by the µ-SPE method. The limit of detection was 0.075 mg/kg, and the recoveries were found to be in the range of 88.9-106.4%. This method is simple, environmentally friendly, and can be used for the determination of indole auxin contents in green bean sprouts quickly and accurately.

Preparation of a stoichiometric molecularly imprinted polymer for auramine O and application in solid-phase extraction.

We describe a stoichiometric approach to the synthesis of molecularly imprinted polymers specific for auramine O. Using the stoichiometric interaction in molecular imprinting, no excess of binding sites is necessary and binding sites are only located inside the imprinted cavities. The free base of the template was obtained to facilitate the interaction with the monomers. Itaconic acid was selected as the functional monomer, and stoichiometric ratio of the interaction with the free base was investigated. The molecularly imprinted polymer preparation conditions such as cross-linker, molar ratio, porogen were optimized as divinylbenzene, 1:2:20 and chloroform/N,N-dimethylformamide, respectively. Under the optimum conditions, a good imprinting effect and very high selectivity were achieved. A solid-phase extraction method was developed using the molecularly imprinted polymers as a sorbent and extraction procedure was optimized. The solid-phase extraction method showed a high extraction recovery for auramine O in its hydrochloride form and free form compared to its analogues. The results strongly indicated that stoichiometric imprinting is an efficient method for development of high selectivity molecularly imprinted polymers for auramine O.