Mariana Roberto Gama

Nano-liquid chromatography in pharmaceutical and biomedical research.

Miniaturized separation techniques have emerged as environmentally friendly alternatives to available separation methods. Nano-liquid chromatography (nano-LC), microchip devices and nano-capillary electrophoresis are miniaturized methods that minimize reagent consumption and waste generation. Furthermore, the low levels of analytes, especially in biological samples, promote the search for more highly sensitive techniques; coupled to mass spectrometry, nano-LC has great potential to become an indispensable tool for routine analysis of biomolecules. This short review presents the fundamental aspects of nano-LC analytical instrumentation, discussing practical considerations and the primary differences between miniaturized and conventional instrumentation. Some theoretical aspects are discussed to better explain both the potential and the principal limitations of nano-LC. Recent pharmaceutical and biomedical applications of this separation technique are also presented to indicate the satisfactory performance for complex matrices, especially for proteomic analysis, that is obtained with nano-LC.

Molecularly imprinted polymers for bioanalytical sample preparation.

Molecularly imprinted polymers (MIP) are stable polymers with molecular recognition abilities, provided by the presence of a template during their synthesis, and are excellent materials with high selectivity for sample preparation in bioanalytical methods. This short review discusses aspects of MIP preparation and its applications as a sorbent material in pharmaceutical and biomedical analysis. MIP in different extraction configurations, including classical solid-phase extraction, solid-phase microextraction, magnetic molecularly imprinted solid-phase extraction, microextraction by packed sorbent and solid-phase extraction in pipette tips, are used to illustrate the good performance of this type of sorbent for sample preparation procedures of complex matrices, especially prior to bioanalytical approaches.

Improvement in Liquid Chromatographic Performance of Organic Polymer Monolithic Capillary Columns with Controlled Free-Radical Polymerization.

Capillary columns containing butyl or lauryl methacrylate monoliths were prepared using two different free-radical polymerization methods: conventional free-radical polymerization and controlled/living free-radical polymerization, both initiated thermally, and these methods were compared for the first time. Both monolith morphology and chromatographic efficiency were compared for the synthesized stationary phases using scanning electronic microscopy (SEM) and capillary liquid chromatography, respectively. Columns prepared using controlled method gave better chromatographic performance for both monomers tested. The lauryl-based monolith showed 7-fold improvement in chromatographic efficiency with a plate count of 42,000 plates/m (corrected for dead volume) for a non-retained compound. Columns fabricated using controlled polymerization appeared more homogenous radially with fused small globular morphologies, evaluated by SEM, and lower column permeability. The columns were compared with respect to resolving power of a series of alkylbenzenes under isocratic and gradient elution conditions.

O Estado da arte da cromatografia líquida bidimensional: conceitos fundamentais, instrumentação e aplicações

The constant evolution of science and the growing demand for new technologies have led to new techniques in instrumentation that can improve detection, separation, resolution, and peak capacity. Comprehensive two-dimensional liquid chromatography (LC×LC) is presented as a powerful tool in complex sample analyses. During an analysis, a sample is subjected to two independent separation mechanisms that are combined, resulting in increased resolving power. For appropriate application of LC×LC, understanding the influence of parameters that require optimization is necessary. The main purpose of optimization is to predict the combination of stationary phases, separation conditions, and instrumental requirements to obtain the best separation performance. This review discusses theoretical, intrumental, and chemometric aspects of LC×LC and focuses on its applications in foods. It aims to provide a clear understanding of the aspects that can be used as strategies in the optimization of this analytical method.

Nanomaterials in Liquid Chromatography: Recent Advances in Stationary Phases

Abstract The preparation, properties, and application of novel nanostructured materials have been a major scientific importance during the past decade, with remarkable impacts on research and the application of analytical chemistry. The search for new stationary phases for diverse chromatographic techniques to provide improvements in analyte selectivity and retention have increased the application of nanomaterials for chromatographic purposes. The development of novel phases has been focused, especially for poorly retained analytes, on modification of available stationary phases. This chapter presents a revision of nanomaterials as stationary phases for liquid chromatography, discussing carbon-based nanomaterials, different nanoparticles, and other nanomaterials used in liquid chromatographic separations.

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.

Controlled crosslinking of trimethylolpropane trimethacrylate for preparation of organic monolithic columns for capillary liquid chromatography

Organic monolithic columns based on single crosslinking of trimethylolpropane trimethacrylate (TRIM) monomer were prepared in a single step by living/controlled free‐radical polymerization. Full optimization of the preparation, such as using different percentages of TRIM and different amounts of radical promoter as well as various porogen solvents were explored. The resulting monolithic columns were characterized by scanning electronic microscopy and nitrogen sorption for structure morphology studies and surface area measurements, respectively. Using capillary liquid chromatography, 150 μm i.d. columns were applied to separate a mixture of small hydrophobic molecules. The results indicated that column performance is highly sensitive to the type and the amount of porogen solvents used in the polymerization mixture composition. Good resolution factors and methylene selectivity were obtained, indicating the promising potential of this material for capillary liquid chromatography separations.