Mohamed Bouri

A filter paper sputtered with a layer of Pt and subsequently coated with a Nafion® membrane is used as working electrode. The mixed potential of the Pt electrode allows the detection of H₂O₂ generated by the oxidation of galactose in the presence of the galactose oxidase enzyme. This provides a simple and mediator‐free approach method. The system shows sensitivity values of −62.8±9.4 mV/decade of galactose in the range from 0.3 to 31.6 mM, well within the clinical relevant range. MnO₂ nanoparticles were added to decrease the interference from ascorbic acid so that validation of the sensor in whole blood samples was performed with good recovery.

A new method for the fluorimetric determination of L-cysteine in wound care dressings is reported using coated fluorescein gold nanoparticles. The procedure was performed with a continuous flow manifold to automate the process to improve the precision. Aqueous gold nanoparticles (size: 10.5 ± 1.2 nm) that were noncovalently adsorbed to fluorescein were employed for the determination of L-cysteine. The fluorescence of the fluorescein-gold nanoparticle compound was lower than the fluorescein fluorescence and increased in the presence of L-cysteine due to fluorescence resonance energy transfer. The fluorescence of the solution containing the fluorescein-gold nanoparticles was enhanced by a factor of 7.5 following the addition of L-cysteine. This effect was not observed when other amino acids were introduced. This fluorescence enhancement was used for the determination of L-cysteine. Good linearity was observed from 0.8 to 4.1 µM of L-cysteine, and the detection limit was 0.1 µM. The method was successfully employed to determine L-cysteine in wound care dressings.

A simple and rapid methodology to separate and characterize gold nanoparticles (AuNPs) in aqueous medium by capillary electrophoresis–evaporative light scattering detection (CE–ELSD) is presented.

An improved and efficient method for the determination of underivatized amino acids based on the use of CE coupled to evaporative light scattering detector (ELSD), involving carbon nanotubes, was successfully developed. Carboxyled single‐walled carbon nanotubes were used for the first time to perform the clean‐up of the analyzed samples, which were afterwards analyzed by CE‐ELSD. White tea samples were used to demonstrate the usefulness of the CE‐ELSD coupled methodology. A suitable interface, based on a triple tube design sprayer, was developed and successfully used for coupling both instruments. Parameters affecting the separation and determination, including the elimination of interferences, were studied and properly optimized. Under the optimized conditions good resolution was achieved for the separation of seven amino acids. The precision of the method, expressed as RSD, was found within the 3.5–5.3% range. The LOD obtained for the proposed method were in the 1.2–2.1 pg range and the LOQ, were in the 2.0–11.5 pg range, with injection pressure of 5 KPa for 20 s (15.3 nL). This method is simple, rapid, and selective compared with other conventional techniques.

In this technical note, an interface for coupling commercially available capillary electrophoresis (CE) equipment to an evaporative light scattering detector (ELSD) is described. The nebulization process was identified as the most critical parameter for performing the reliable coupling between both pieces of equipment. Therefore, appropriate modifications in the nebulization chamber and in the conventional nebulizer were brought to make ELSD fully compatible with CE. The impact of the customized interface on CE separation and detection was evaluated in terms of resolution and sensitivity. ELSD can be considered as an attractive alternative to other CE detection systems (e.g., UV-vis, fluorescence, electrochemical detection, or even MS detection), particularly those in which derivatization is needed. This advantage is due to the versatility and the quasi-universality of ELSD. Thus, sensitive and fast separations of several compounds were performed using this CE-ELSD customized arrangement, which opens up an interesting analytical potential for the determination of compounds not presenting sensitive UV-vis chormophore, fluorophore, or electroactive groups. Carbohydrates were selected in this work to demonstrate the applicability of CE-ELSD coupling.

This review, with more than 170 references, presents a general overview of the use of magnetic nanoparticles (MNPs) to perform sample preparation. In this way, the main types of MNPs used for this purpose, such as magnetic molecularly imprinted polymer (MMIP), noble metal coated MNPs, carbon nanotubes (CNTs), quantum dots (QDs), silica, and surfactant are described in terms of their composition, properties, and synergetic potential. Finally, some examples of their analytical applications are reported, as well as pointing out possible future applications of MNPs in the analytical field.

A magnetic material based on N-methylimidazolium ionic liquid and Fe₃O₄ magnetic nanoparticles incorporated in a silica matrix has been used to extract and preconcentrate sulfonylurea herbicides, such as thifensulfuron methyl (TSM), metsulfuron methyl (MSM), triasulfuron (TS), tribenuron methyl (TBM) and primisulfuron methyl (PSM) from polluted water samples, prior to their analysis by capillary liquid chromatography with a diode array detector (DAD). Under the optimum conditions, this method allows the determination of TSM, MSM, TS, TBM and PSM in a linear range between 5 and 100 ng mL⁻¹, with relative standard deviation values lower than 5.3 % (n = 10), in all cases. Detection limits ranging between 1.13 and 2.95 ng mL⁻¹ were achieved. The usefulness of the proposed method was demonstrated by the analysis of river water samples, obtaining recoveries higher than 91 %. Figure  

Dissipation of bifenthrin and λ-cyhalothrin pyrethroid insecticides, under environmental conditions, was evaluated on green beans grown in experimental greenhouses (Souss Massa valley, Morocco). Pesticide residues were determined by gas chromatography with micro electron-capture detector (GC-μECD) after dichloromethane extraction and cleanup on florisil phase cartridges. In the case of field experiments, a random block scheme was employed. Each block contained 25 plants in a single row and tests were carried out in triplicates applying pesticides at the recommended doses by the manufacturers. Fruit samples were periodically taken until the end of the preharvest interval (p.i.). The results obtained showed that the p.i of bifenthrin in green bean were 4 days in the winter and 3.5 days in the spring, whereas that for λ-cyhalothrin 8 days was found in the winter and 7.5 days in the spring. Consequently, it is possible to consider the European Union maximum residue limit (EU MRL) values compatible with the proper agricultural practices used for growing green bean in the plastic greenhouse of Souss Massa valley in South Morocco. Bifenthrin had a degradation of first-order kinetics, whereas that of levels for λ-cyhalothrin residue can not be interpreted by the use of a first order model.