Functionalized carbon nanotubes as the pseudostationary phase for capillary EKC separation of non‐steroidal anti‐inflammatory drugs

Abstract

Functionalized multiwalled carbon nanotubes (f-MWCNTs) can serve as the pseudostationary phase (PSP) for the capillary EKC separation of non-steroidal anti-inflammatory drugs (NSAIDs). To increase their hydrophilicity, we treated MWCNTs, with a sonochemical process in a concentrated nitric/sulfuric acid mixture. The oxidized MWCNTs were then characterized by FT-IR, transmission electron microscopy, and X-ray photoelectron spectroscopy. We evaluated the potential of the PSP and the effects of buffer composition, pH, addition of organic modifier, and injection temperature on the NSAID separation. The PSP created a network structure of pi-pi interactions, hydrophobic forces, hydrogen bonding, and electrostatic interactions to separate NSAIDs, providing a different separation mode from SDS micelles. We achieved complete separation of six NSAIDs using a mixture of a borate buffer (75 mM, pH 10) with methanol (5%, v/v) containing 0.02 mg/mL f-MWCNTs, an applied voltage of +12 kV and detection at 214 nm. Better precision was obtained with a low injection temperature. The method was also satisfactorily applied to the analysis of NSAIDs spiked into a urine sample.

Hydrophilic interaction electrokinetic chromatography using bio‐based nanofillers

“…In our preliminary experiment, we found that these bio‐based nanofillers could be dispersed as colloids in the solution containing much organic solvent, where HI would be effective. Although several papers have already reported EKC with NFs like carbon nanotubes , its use has been limited to hydrophobic interaction. To our knowledge, additionally, no research has been reported on the separation with bio‐based nanomaterials.…”

Amperometric detection in the presence of carbon nanotubes dispersed in background electrolyte: Evaluating its suitability for capillary electrokinetic chromatography separations of polyphenolic compounds

“…In all cases, stable responses were obtained without baseline noise increasing, thus indicating that the ECD coupled to capillary electrophoresis allows working with BGE containing CNTs concentrations of, at least, 24 mg/L. This maximum CNTs concentration is eight times higher than that previously reported for UV‐vis detection . Figure shows the HDVs for catechol obtained in different BGEs.…”

“…Only one group has evaluated the applicability of a portable CE system with contactless conductivity detection, incorporating carboxylated multiwalled CNTs into BGE containing polyvinylpyrrolidone . Several authors have commented on the interference of CNTs with the UV‐vis detection systems and reported maximum nanotube concentrations ranging from 3.2 mg/L for SDS‐coated single‐walled CNTs and multiwalled CNTs , over 20 mg/L for functionalized multiwalled CNTs , to 0.8 mg/L for multiwalled CNTs dispersed with sodium dodecylbenzenesulphonate . Clearly, the assessment of compatibility with the detection system and the corresponding threshold concentration value remains to be determined on a case‐by‐case scene.…”

CE and nanomaterials – Part II: Nanomaterials in CE

“…MWCNTs – especially their functionalization – have also attracted attention. Nitric, sulfuric, and hydrochloric acids have been used to increase their hydrophilicity, and MWCNTs functionalized in this way have been used for the separation of non‐steroidal anti‐inflammatory drugs . Subunits of functionalized MWCNTs and borate buffer at pH 10 were satisfactory for the separation of six non‐steroidal anti‐inflammatory drugs and for the analysis of a spiked urine sample .…”