Design of double-core-shell structural materials for the extraction of non-steroidal anti-inflammatory drugs.

In this work, core-shell material with a special structure was designed and applied in solid-phase extraction (SPE) for non-steroidal anti-inflammatory drugs (NSAIDs) combined with high-performance liquid chromatography. Based on the advantages of core-shell ZIF-8@ZIF-67 (Zeolite imidazole ester framework materials [ZIFs]), effective derivatization treatment was carried out to partially vulcanize the original ZIFs, resulting in a special and new double-core-shell structural material CoS/ZIF-67/ZnS/ZIF-8 (ZIFs@ZnS@CoS) with porous surface and center hollow. The multiple forces caused by the rich chemical structure, the large specific surface area caused by the special pore structure, and the effective protection of the ZIFs core by sulfide shell make the designed material have higher extraction efficiency and longer service life, compared with ZIF-8@ZIF-67 and ZIF-8. At the same time, the established analytical method for non-steroidal drugs had a high recovery rate (98.93%-102.10%), low detection limit (0.11-0.27 µg/L), and wide linear range (1-200 µg/L) within a good correlation coefficient R2 (0.9978-0.9993). Satisfactory results were also obtained from the extraction of NSAIDs from the Yellow River water samples. These results indicate that the designed double-core-shell structure material can effectively exert its structural advantages and become a promising extraction material.

MIL-101(Fe)@TiO2 nanotube composite material is used for the solid phase extraction of non-steroidal anti-inflammatory drugs under the synergy of multiple interactions.

Increasing the adsorption sites and effective interactions between sorbents and the targets can improve the solid-phase extraction (SPE) efficiency. Herein, based on the advantages of MOFs and TiO2 nanotubes (TiO2 NTs), an MIL-101(Fe)@TiO2 NT composite was prepared and applied to extract non-steroidal anti-inflammatory drugs (NSAIDs) from water samples coupled with high performance liquid chromatography (HPLC). Through characterization, it was established that MIL-101(Fe) was effectively composited on the surface and inside the TiO2 nanotubes, increasing effective adsorption sites. The obtained composite material well retains the structure and functional groups of the two original materials, and while retaining the original force with the target, it achieves a synergistic effect and produces more interactions with the target. Therefore, the extraction efficiency was greatly improved. The recovery efficiency reached 97.7-105.1% with an RSD of less than 6.71%, the detection limit was 0.1-0.2 µg L-1, and the linear range was 1-200 µg L-1 with a determination coefficient of 0.9972-0.9994. Owing to the stability of the two original materials, the composite material could be recycled and reused to extract NSAIDs up to 15 times without a loss of the recovery rate. Satisfactory results were obtained when it was used to extract NSAIDs from the Yellow River. These results indicate that the synthesized MIL-101(Fe)@TiO2 NT material is a promising sorbent to extract NSAIDs at trace concentrations with high efficiency and long lifetimes.

A magnetic MOF derivative with rich interactions formed under mild preparation conditions for the extraction of non-steroidal anti-inflammatory drugs from the Yellow River.

For sorbents, good magnetic properties and rich interactions with targets are important ways to improve the efficiency of magnetic solid-phase extraction (MSPE). The magnetic MOF-101 derivative (MD) was obtained by heat-treating MOF-101 at different temperatures. After a series of characterizations, it was found that MD-350 had the best magnetic properties and retained more functional groups of the original MOF-101, and had better extraction efficiency as compared to MD obtained under other treatment temperatures for the MSPE of four non-steroidal anti-inflammatory drugs (NSAIDs) in water samples, coupled with high-performance liquid chromatography (HPLC). The remaining functional groups of MD-350 can produce more interactions with NSAIDs, such as hydrogen bonding, π-π conjugation, and coordination interactions; good magnetic properties facilitate the separation of the sorbent and the solution. These advantages indicate that the established extraction method demonstrated satisfactory extraction performance: an excellent recovery rate (96.73-100.61%) with a short extraction time (15 min), a wide linear range (4-400 µg L-1) with a determination coefficient of 0.9975-0.9993, a low LOD of 0.2-0.5 µg L-1 and up to 12 times service-life without the loss of the recovery rate. Satisfactory results were also obtained in extracting NSAIDs from Yellow River. All these results indicate that MD-350 prepared under mild conditions has potential as an MSPE sorbent to detect and remove NSAIDs from environmental waters with high efficiency and long service life.

An Ag2 S@ZnS-coated fiber for efficient, long-life solid-phase microextraction of polycyclic aromatic hydrocarbons in water.

Although an efficient and stable fiber coating is essential for the development of solid-phase microextraction technique, it remains a challenging prospect. Herein, an inorganic nanocomposite material Ag2 S@ZnS was prepared and used as a coating for fibers to detect polycyclic aromatic hydrocarbons in water samples in combination with a GC with flame ionization detector. Compared with a single ZnS material, the Ag2 S@ZnS composite shows many uneven nano-protrusions on the surface of the microspheres. In conjunction with the relatively scattered microstructure of the coating and the effective anion-π interaction formed between ZnS and the hydrocarbons, it has a large specific surface area, fast diffusion of the target molecule on its surface, and appropriate adsorption of the target molecules; therefore, it exhibits good extraction efficiency for the hydrocarbons. Under optimal conditions, the proposed analytical method exhibits superior performance with good linearity (0.01-500 µg/L) and low limits of detection (0.001-0.200 µg/L). Combined with high thermal, chemical, and mechanical stability, the service life of the coating was improved and could be used 200 times without a significant reduction in the extraction performance, and at least 2000 extraction-desorption cycles can be achieved. Satisfactory results were also obtained for the real samples.

Durable molybdenum oxide coated solid-phase microextraction fiber for highly selective and efficient extraction of polycyclic aromatic hydrocarbons in water.

A bonding method was developed for coating molybdenum oxides onto a steel wire substrate, which was used as a solid-phase microextraction fiber, was coupled with gas chromatography. Based on the characterization, it is found that the as-prepared molybdenum oxides material contained a nanobelt structure with a uniform size and good dispersibility. In addition, there were a large number of small protrusions on the surface of the nanobelts. These characteristics provided a large specific surface area for extraction. Molybdenum oxides exhibited a high extraction selectivity for polycyclic aromatic hydrocarbons owing to its moderate coordination. After the optimization of the factors, method detection limits of < 1.25 µg/L were achieved, and the calibration curves were linear within the range of 2-600 µg/L. In addition, repeatability was demonstrated, and the relative standard deviation < 6.4%. The molybdenum oxides coating had a high scratch resistance, which could effectively prevent coating wear and failure. Combined with the high thermal and chemical stability, the service life of the coating was improved and could be used 150 times without a significant reduction in the extraction performance. Finally, the as-prepared fiber had a comparable extraction capacity and higher partition coefficients that those of commercial polyacrylate fibers.