Magnetic Solid-Phase Extraction Based on Magnetite-Multiwalled Carbon Nanotubes of Non-Steroidal Anti-Inflammatories from Water Followed by LC-ESI-MS/MS

An analytical method based on liquid chromatography-electrospray ionization-tandem mass spectrometry detection (LC-ESI-MS/MS) has been developed for the determination of pharmaceutical compounds in water samples. Five non-steroidal anti-inflammatory drugs (NSAIDs) namely Naproxen, Ketoprofen, Piroxicam, Diflunisal and Celecoxib were investigated. Magnetic solid phase extraction (MSPE) was used for sample pre concentration of water samples and magnetic carbon nanotubes (Fe3O4-MWCNTs) were considered as solid phase extraction sorbent. Important parameters influencing the extraction efficiency such as nature and volume of eluent, sample pH and adsorbent mass were optimized. The developed MSPE method involved 75 mg of Fe3O4-MWCNTs sorbent, 5 mL of water sample at pH = 4 and 5 mL of 10% ammonia in methanol in the elution step. Under the optimized extraction conditions, linearity, detection and quantification limits and reproducibility were evaluated. The proposed method was successfully applied to the analysis of NSAIDs in surface waters, and mean recoveries of all the NSAIDs were above 90% with relative standard deviations < 17%. The detection and quantification limits were comprised between 0.05-3.6 ng.mL-1 and 0.2-11.9 ng.mL-1, respectively.

An MD-based systematic study on the mechanical characteristics of a novel hybrid CNT/graphene drug carrier

This paper is aimed to assess the mechanical properties of a hybrid graphene-carbon nanotube carrier embedded with doxorubicin (DOX). Utilizing molecular dynamics simulation, the results reveal that by increasing the temperature from 309 to 313 K, the elastic modulus of the GS/CNT/DOX carrier decreases from 0.8 to 0.74 TPa. Also, it is shown that the presence of chitosan molecules enhances the mechanical characteristics of the proposed nanocarrier. Taking the chirality of the graphene sheet into account, the results indicate that by increasing the size of the graphene sheet, the failure stress is slightly increased for the armchair type. However, this value decreases as the size of the zigzag sample increases. Additionally, the influence of aspect ratio on the elastic modulus, fracture stress, and fracture strain of these systems is systematically examined. It has been shown that the failure stress may change significantly with increasing this parameter, especially for carrier systems having zigzag carbon nanostructures. Moreover considering various voids content in the CNT structure, the weakening effect of defects is systematically explored. Also, the dependence of the mechanical features of the proposed hybrid carrier on the presence of DOX molecules is studied via MD simulations. Finally, we have investigated the role of CNT physical characteristics including its size and chirality on the results. Graphical abstract.

Adsorptive removal of aqueous bezafibrate by magnetic ferrite modified carbon nanotubes

MFe₂O₄/CNTs were synthesized and successfully applied for the removal of aqueous bezafibrate. The adsorption behavior and mechanism were elucidated in detail.