Alginate-based hydrogel fiber as a restricted access material for microextraction of drugs in biological samples.

A novel lab-made alginate-based hydrogel device was successfully prepared and applied as a sorption material for the solid-phase microextraction of drugs (fluoxetine and its metabolite, norfluoxetine) in human plasma, with subsequent determination by high performance liquid chromatography-fluorescence detection (HPLC-FD). When supported in a polypropylene hollow fiber, the alginate was able to extract the analytes and functioned as a restricted access material, excluding >95 % of proteins from the biological matrix. The results indicate the potential use of this phase/device for quantitative drugs extraction from biological matrices at concentrations compatible with those typical in the literature (0.5 µg mL-1), and with satisfactory precision (13.4 % for fluoxetine and 6.2 % for norfluoxetine). Such outcomes, promoted by a simple and inexpensive material, open a new perspective of exploration of hydrogels as the sorption phase in biological matrices, a concept previously unexplored in the literature.

Polypyrrole nanotubes for electrochemically controlled extraction of atrazine, caffeine and progesterone.

Polypyrrole (PPy) was electrochemically synthesized with charge control on the surface of a steel mesh. Two different morphologies (globular and nanotubular) were created and characterized by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The modified electrodes were used as extraction phases in solid-phase extraction (SPE) and electrochemically controlled solid-phase extraction (EC-SPE) of atrazine, caffeine and progesterone. Raman spectroscopy was employed for the structural characterization of PPy after long exposure to the analytes. The electrochemical behavior was studied by cyclic voltammetry which revealed the higher capacitive behavior of polypyrrole nanotubes because of the huge superficial area, also no electrocatalytical behavior was observed evidencing the strong adsorption of the analytes on the PPy surface. The effects of the PPy oxidation state on the extraction performance were evaluated by in-situ electrochemical sorption experiments. The sorption capacity was evaluated by gas chromatography coupled to mass spectrometry (GC-MS). The method displays good stability, repeatability and reproducibility. The limits of detection range between 1.7-16.7 µg L-1. Following the extraction of river water samples, it was possible to identify the presence of other endogenous organic compounds besides the analytes of interest. This indicates the potential of the method and material developed in this work. Graphical abstract Schematic representation of a steel mesh electrode covered with polypyrrole nanotubes used as extraction phase for separation of contaminants from aqueous samples. The oxidation level of polypyrrole was electrochemically tuned by which the adsorption of analytes is deeply affected.

Physical-chemical characteristics and potential use of a novel alginate/zein hydrogel as the sorption phase for polar organic compounds.

A novel alginate based hydrogel was successfully prepared and tested for the solid phase microextraction of medium-to-high polarity compounds, when supported in a polypropylene (PP) fiber. Pure alginate when added onto the surface of the PP fiber, resulted in a significant improvement in the extraction efficiency of the analytes (except for ß-estradiol). The alginate hydrogel was modified upon the incorporation of a small amount of zein, a corn protein. Interestingly, the alginate/zein-supported hydrogel was capable of successfully extracting compounds with low partition constant (Kow), such as 17-α-ethinyl estradiol, progesterone and estriol, since the initial water uptake decreased dramatically in this gel, therefore, leaving the alginate hydroxyl groups more available to interact with the polar compounds. In conclusion, this paper presents the preparation of a simple, low cost, reusable, and efficient sorption phase for the extraction of polar compounds with different polarities in aqueous samples, which is a current technological challenge in developing efficient wastewater treatment.

Biocompatible in-tube solid phase microextraction coupled with liquid chromatography-fluorescence detection for determination of interferon α in plasma samples.

The present work demonstrates the successful application of automated biocompatible in-tube solid-phase microextraction coupled with liquid chromatography (in-tube SPME/LC) for determination of interferon alpha(2a) (IFN α(2a)) in plasma samples for therapeutic drug monitoring. A restricted access material (RAM, protein-coated silica) was employed for preparation of a lab-made biocompatible in-tube SPME capillary that enables the direct injection of biological fluids as well as the simultaneous exclusion of macromolecules by chemical diffusion barrier and drug pre-concentration. The in-tube SPME variables, such as sample volume, draw/eject volume, number of draw-eject cycles, and desorption mode were optimized, to improve the sensitivity of the proposed method. The IFN α(2a) analyses in plasma sample were carried out within 25min (sample preparation and LC analyses). The response of the proposed method was linear over a dynamic range, from 0.06 to 3.0MIUmL(-1), with correlation coefficient equal to 0.998. The interday precision of the method presented coefficient of variation lower than 8%. The proposed automated method has adequate analytical sensitivity and selectivity for determination of IFN α(2a) in plasma samples for therapeutic drug monitoring.