Carla Grazieli Azevedo da Silva

APLICAÇÕES DE CROMATOGRAFIA LÍQUIDA DE ALTA EFICIÊNCIA PARA O ESTUDO DE POLUENTES ORGÂNICOS EMERGENTES

Emerging organic pollutants (EOP) include many environmental contaminants based on commercial products such as pharmaceuticals, personal care products, detergents, gasoline, polymers, etc. EOP may be candidates for future regulation as they offer potential risk to environmental and human health due to their continual entrance into the environment and to the fact that even the most modern wastewater treatment plants are not able to totally transform / remove these compounds. High performance liquid chromatography is recommended to separate emerging organic pollutants with characteristics of high polarity and low volatility, especially pharmaceuticals, from environmental matrices.

Aplicações de cromatografia líquida de alta eficiência para o estudo de poluentes orgânicos emergentes

Emerging organic pollutants (EOP) include many environmental contaminants based on commercial products such as pharmaceuticals, personal care products, detergents, gasoline, polymers, etc. EOP may be candidates for future regulation as they offer potential risk to environmental and human health due to their continual entrance into the environment and to the fact that even the most modern wastewater treatment plants are not able to totally transform / remove these compounds. High performance liquid chromatography is recommended to separate emerging organic pollutants with characteristics of high polarity and low volatility, especially pharmaceuticals, from environmental matrices.

Preparation and characterization of a poly(methyloctadecylsiloxane) thermally immobilized onto zirconized silica stationary phase for high-performance liquid chromatography

This study describes the preparation and characterization of a HPLC stationary phase (SP) obtained by deposition of poly(methyloctadecylsiloxane) (PMODS) onto the surface of porous zirconized silica particles, followed by thermal immobilization. The SP were characterized using elemental analysis and infrared and (29)Si NMR spectroscopies, while their chromatographic behaviors were investigated by separation of selected neutral, acidic and basic compounds of different test mixtures (Engelhardt, SRM 870 and Tanaka tests). The preparation of the metalized support and the thermal immobilization of PMODS onto zirconized silica, optimized by experimental design, produced a SP based on PMODS that showed high values of efficiency (up to 85000 plates/m) and appropriate asymmetry factors. The presence of zirconium on the surface significantly decreases silica solubility in severe conditions (alkaline mobile phase at pH 10 and high temperature), increasing column lifetime.

Super/subcritical fluid chromatography with packed columns: state of the art and applications

Separations using supercritical fluid chromatography (SFC) with packed columns have been re-discovered and explored in recent years. SFC enables fast and efficient separations and, in some cases, gives better results than high performance liquid chromatography (HPLC). This paper provides an overview of recent advances in SFC separations using packed columns for both achiral and chiral separations. The most important types of stationary phases used in SFC are discussed as well as the most critical parameters involved in the separations and some recent applications.

Improved chemical stabilities for end-capped high performance liquid chromatography stationary phases based on poly(methyloctadecylsiloxane) thermally immobilized onto metalized silicas.

Endcapped stationary phases were prepared after thermal immobilization of poly(methyloctadecylsiloxane) (PMODS) onto zirconized and titanized silica supports. These new stationary phases have lower densities of residual hydroxyl groups, according to infrared spectroscopy and 29Si CP-MAS NMR and as shown by the symmetrical peaks of basic compounds from the Tanaka, Engelhardt and SRM 870 test mixtures. Stability tests for the endcapped stationary phases, measured using severe alkaline conditions (70:30 (v/v) methanol:0.05 mol/L K2CO3/KHCO3, pH 10, 50 °C), revealed that the stabilities of these phases are greater than the stabilities of similar nonendcapped phases. The stationary phases showed good performance for the separation of basic pharmaceuticals.

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.

CROMATOGRAFIA POR INTERAÇÕES HIDROFILICAS (HILIC): ESTADO DA ARTE E APLICAÇÕES

Hydrophilic interaction liquid chromatography (HILIC) has been gaining increased attention for its effective separation of highly polar compounds, which include carbohydrates, amino acids, pharmaceutical compounds, proteins, glycoproteins, nucleosides, etc. Polar compounds are usually poorly retained on reverse-phase liquid chromatography (RP-HPLC) columns or have poor solubility in the apolar mobile phase of normal-phase high performance liquid chromatography (NP-HPLC). Since HILIC uses organic solvents such as ACN or MeOH ( > 70%), also used in RP-HPLC and polar stationary phases similar to NP-HPLC (bare silica, diol, amino, amide, saccharide, zwitterionic stationary phases, etc.), it represents a hybrid of the two separation modes. The high organic content in the MP leads to good compatibility with mass spectrometry (MS), increasing the detectivity. This review describes the fundamentals of HILIC and highlights some interesting applications.

3-Dimensional X-ray microtomography methodology for characterization of monolithic stationary phases and columns for capillary liquid chromatography - A tutorial

In this tutorial we describe a fast, nondestructive, three-dimensional (3-D) view approach to be used in morphology characterization of capillary monoliths and columns by reconstruction from X-ray microtomography (XMT) obtained by acquiring projection images of the sample from a number of different directions. The method comprises imaging acquisition, imaging reconstruction using specific algorithms and imaging analysis by generation of a 3-D image of the sample from radiographic images. The 3-D images show the morphological data for bulk macropore space and skeleton connectivity of the monoliths and were compared with other images from imaging techniques such as scanning electron microscopy (SEM) and field emission scanning electron microscopy (FESEM) and with chromatographic performance. The 3-D XMT methodology is applicable for organic and inorganic capillary chromatographic monolithic materials and it allows the acquisition of many hundreds (in our case 1001 projections) of longitudinal and cross-sectional images in a single session, resolving morphological details with a 3D-view of the monolithic structure, inclusive inside the column in a sectional structure with volume (three dimensions) when compared to the sectional structure area (with only two dimensions) when using SEM and FESEM techniques.

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.