Synthesis and evaluation of a pentafluorobenzamide stationary phase for HPLC separations in the reversed phase and hydrophilic interaction modes.

A pentafluorobenzamide stationary phase was synthesized by an easy method with no intermediate purification steps. Physicochemical characterization (elemental analysis, fourier transform infrared spectroscopy, 29 Si and 13 C nuclear magnetic resonance spectroscopy) confirmed the presence of pentafluorobenzamide functionalization on the surface of the silica particles. The pentafluorobenzamide stationary phase proved to be quite versatile as it can be used in two different modes in liquid chromatography: reversed phase and hydrophilic interaction liquid chromatography. Chromatographic characterizations in both modes confirmed the multiple interactions established by the new stationary phase, such as hydrogen bonding and π-π and ion-exchange interactions. The pentafluorobenzamide stationary phase was successfully employed for the separation of nucleosides and antihypertensive drugs under hydrophilic interaction liquid chromatography conditions, as well as pesticides and benzodiazepine using reversed phase conditions. The stationary phase showed significant potential when compared with commercial columns.

Pesticide determination in sweet peppers using QuEChERS and LC-MS/MS.

In this work, a rapid, effective, and safe method, generating only a small amount of waste, based on the citrate version of QuEChERS was optimized and validated for multiresidue determination of pesticides of different classes in sweet green peppers, determined by liquid chromatography coupled with tandem mass spectrometry. The matrix components influenced the measurement of the pesticides by the developed analysis technique, so that, analytical curves were prepared using pesticide-free matrix extracts for quantification of the analytes. The method provides satisfactory accuracy verified by recoveries of 70-120%, and good precision (coefficients of variation ≤20%). It also showed selectivity, linearity of response, and lower limits of quantification than the maximum limit of residue for each compound, as established by ANVISA and Codex Alimentarius.

Permeation profiles of resveratrol cream delivered through porcine vaginal mucosa: Evaluation of different HPLC stationary phases.

Trans-resveratrol affects biological systems in a multitude of ways, but its oral bioavailability is remarkably poor due to in vivo metabolization. This drawback has fomented the development of new strategies for systemic delivery, such as transmucosal delivery via the vaginal route, which is our main focus here. In this sense, our pioneering study purposed to evaluate the trans-resveratrol permeation efficacy through this route. For that, we used a previously validated method and tested it with three different stationary phases: a commercial C18 column and two laboratory-made chromatographic columns containing poly(methyloctadecylsiloxane) (PMODS) thermally immobilized onto zirconized silica (Zr-PMODS) or titanized silica (Ti-PMODS). The permeation experiments showed that resveratrol, in the formulation used, was not successfully delivered to the bloodstream - it was actually retained within the vaginal mucosa, which suggests a local use rather a systemic one.

In vitro drug release and ex vivo percutaneous absorption of resveratrol cream using HPLC with zirconized silica stationary phase.

Since the designs of optimal formulations for resveratrol permeation via the skin are lacking, the aim of this study was to establish the profile of resveratrol permeability into and across human skin. For that, a laboratory-made chromatographic column was used (Zr-PMODS), with its performance being compared to a traditional C18 column. In vitro drug release was conducted with polysulfone membranes, and the flux (JS) was 30.49 µg cm(-2) h(-1)), with a lag time (LT) of 0.04 h, following a pseudo-first-order kinetics. For ex vivo percutaneous absorption using excised female human skin, the kinetic profile was the same, but JS was 0.87 µg cm(-2) h(-1) and LT was 0.97 h. From the initials 49.30 µg applied to the skin, 9.50 µg were quantified in the receptor medium, 20.48 µg was retained at the stratum corneum (do not account as permeated) and 21.41 µg was retained at the viable epidermis+dermis (account as permeated), totalizing 30.90 µg of resveratrol permeated after 24 h of application (62.6%). From these results, one can conclude that a person using the 1-g emulsion dose released by the pump containing 20mg of resveratrol will have, theoretically, 12.53 mg of it liberated into his bloodstream, gradually and continuously for 24 h.