Graphene and zeolite as adsorbents in bar-micro-solid phase extraction of pharmaceutical compounds of diverse polarities.

A bar micro-solid phase (bar μ-SPE) extraction method using either graphene or zeolite or their mixtures as an adsorbent, coupled with high-performance liquid chromatography (using a C1 column) was developed for the simultaneous determination of pharmaceutical compounds (metformin (MET), buformin (BUF), phenformin (PHEN) and propranolol (PROP)) of diverse polarity (log  from -1.82 to 3.10).

Real-Time Ozone Sensor Based on Selective Oxidation of Methylene Blue in Mesoporous Silica Films.

Sensitive and selective personal exposure monitors are needed to assess ozone (O) concentrations in the workplace atmosphere in real time for the analysis and prevention of health risks. Here, a cumulative gas sensor using visible spectroscopy for real-time O determination is described. The sensing chip is a mesoporous silica thin film deposited on transparent glass and impregnated with methylene blue (MB).

Rapid and reversible adsorption of BTX on mesoporous silica thin films for their real time spectrophotometric detection in air at ppm levels.

Benzene, toluene and xylenes (BTX) are among the most toxic volatile organic compounds that can be emitted into the environment of different workplaces. Regulations to protect workers continue to strengthen permissible exposure limit (PEL), and short-term exposure limit (STEL) for any 15-min period are defined for BTX that should be controlled with rapid, selective and sensitive on-site sensors. For that purpose, a real-time analysis of BTX is described here, using the UV spectrometric determination of instantaneously concentrated pollutants in a thin film of mesoporous and transparent silica deposited onto quartz plates.

Electrochemically Modulated Liquid-Liquid Extraction for Sample Enrichment.

A new sample preparation method is proposed for the extraction of pharmaceutical compounds (Metformin, Phenyl biguanide, and Phenformin) of varied hydrophilicity, dissolved in an aqueous sample. When in contact with an organic phase, an interfacial potential is imposed by the presence of an ion, tetramethylammonium (TMA), common to each phase. The interfacial potential difference drives the transfer of ionic analytes across the interface and allows it to reach up to nearly 100% extraction efficiency and a 60-fold enrichment factor in optimized extraction conditions as determined by HPLC analysis.

Mesoporous Silica Thin Films for Improved Electrochemical Detection of Paraquat.

An electrochemical method was developed for rapid and sensitive detection of the herbicide paraquat in aqueous samples using mesoporous silica thin film modified glassy carbon electrodes (GCE). Vertically aligned mesoporous silica thin films were deposited onto GCE by electrochemically assisted self-assembly (EASA). Cyclic voltammetry revealed effective response to the cationic analyte (while rejecting anions) thanks to the charge selectivity exhibited by the negatively charged mesoporous channels.

Hydrodemetallation and Hydrodesulfurization Spent Catalysts Elemental Analysis: Comparison of Wavelength Dispersive X-ray Fluorescence and Atomic Emission Spectrometries.

Petroleum industries continuously consume catalysts on very large scales. The recycling of spent catalysts is thus of major economic and environmental importance and its first step consists of the characterization of the valuable metal content. Wavelength dispersive X-ray fluorescence (WDXRF) analysis is compared with inductively coupled plasma atomic emission spectrometry (ICP-AES) for the analysis of five samples of spent hydrodesulphurization (HDS) and hydrodemetallization (HDM) catalysts.

Sorption of polluting metal ions on a palm tree frond sawdust studied by the means of modified carbon paste electrodes.

Water remediation by adsorption of the metal ions on a low cost sorbent is the frame of the present study. The metal ions adsorption properties of sawdust of palm tree fronds (PTF sawdust) are investigated by both equilibrium measurements and modified carbon paste electrode. The ability to adsorb Cu(II), Cr(VI) and As(III) in significant quantities is demonstrated.

Conductivity stopped-flow study of the kinetics of solutes uptake by colloidal particles of synthetic resins.

The uptake rates of acids (hydrochloric acid, sulfuric acid, perchloric acid and acetic acid) by colloidal solid particles (mean diameter 0.35 microm) of DEAE (diethylaminoethyl Sephadex) resin was studied by the means of the stopped flow technique equipped with a conductivity detection. This original experimental approach allows to avoid hydrodynamics perturbations during data acquisition.