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A chemically modified electrode was constructed by incorporating manganese (III) tetraphenyl porphyrine into a carbon paste matrix. The modified electrode was used as a sensitive electrochemical sensor for measuring of riboflavin. The constructed electrode exhibited catalytic properties for the electro-oxidation of riboflavin and lowered the over potential for the oxidation of this compound; consequently, the corresponding peak currents of riboflavin increased significantly. The modified electrode showed a near-Nernstian behavior for electro-oxidation of riboflavin hence, it could be a suitable voltammetric sensor for the fast and easy determination of riboflavin. A linear response in concentration range 1.0 × 10 −8 -1.0 × 10 −5 M was obtained with a detection limit of 8.0 × 10 −9 M (S /n = 3) for the determination of riboflavin. The electrode showed long-term stability and the standard deviation of the slope obtained after repeated calibration during a period of 3 months was 3.5% (n = 10). The modified electrode was used for differential pulse voltammetric determination of riboflavin in pharmaceutical and food samples.

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This study deals with poly(lactic acid) (PLA), poly(ε‐caprolactone) (PCL), and their blend electrospun nanofibers (ESNF) as novel systems for the release of levetiracetam (LEV). Scanning electron microscopy demonstrated that the morphology of all samples is smooth and beads‐free. In addition, with increasing LEV content, the average diameters of PLA, PCL, and PCL/PLA ESNF enhanced by almost 69%, 41%, and 14%, respectively. FTIR spectroscopy was utilized to confirm the structure of polymer and drug, polymer‐drug interaction, and the observation of functional groups. The pore percentage was also diminished by adding LEV. The results of x‐ray diffraction revealed that the crystallinity decreased from 18.2%, 40.1%, and 21.5% for PLA, PCL, and PLA/PCL ESNF, respectively, to 15%, 31.2%, and 13.6% for the samples containing 18 wt% LEV. In addition, PLA ESNF containing 10 and 18 wt% LEV demonstrated a steady uptrend for drug release, while PCL and PLA/PCL ESNF containing 10 and 18 wt% LEV initially indicated an abrupt increase in drug release and then became steady. Moreover, drug release kinetics were evaluated using different models such as zero order, first order, Higuchi, and Korsmeyer‐Peppas models and the best model for predicting the drug release behavior was selected.

A fast and efficient method was developed for the extraction and determination of organophosphorus pesticides in water samples. Organophosphorus pesticides were extracted by solid-phase extraction using magnetic multi-walled carbon nanotubes and determined by gas chromatography with ion-trap mass spectrometry. Parameters affecting the extraction were investigated. Under optimum conditions of the method, 10 mg magnetic multi-walled carbon nanotubes were added into 10 mL sample. After 2 min, adsorbent particles settled at the bottom of test tube with a magnet. After removing aqueous supernatant, the analytes were desorbed with acetonitrile. Then, 70 μL of acetonitrile phase was injected into the gas chromatography and mass spectrometry system that had an ion-trap analyzer. To achieve high sensitivity, the large-volume-injection technique was used with a programmed temperature vaporization inlet, and the ion-trap mass spectrometer was operated in single ion storage mode. Under the best conditions, the enrichment factors and extraction recoveries were in the range of 113-124 and 74-103%, respectively. The limits of detection were between 3 and 15 ng/L, and the relative standard deviations were < 10%. This method was successfully used for the determination of organophosphorus pesticides in dam water, lagoon water, and river water samples with good reproducibility and recovery.

A sensitive electrochemical sensor is formed by a carbon nanoparticles (CNPs)/glassy carbon electrode for the determination of antidepressant drug fluoxetine in pharmaceutical formulation. The dependence of fluoxetine electro-oxidation currents and potentials on pH concentration and the potential scan rate was studied. Scanning electron microscopy was used for characterisation of the CNPs. The porous layer of the CNPs improved the electroactive surface area and led to a significant increasing in the peak currents, based on the diffusion within a nanoporous film. The best electrochemical response was obtained from differential pulse voltammograms in the buffer solution (pH 9.0). Linear calibration graphs were obtained in 1-25 µM with %RSD values from 0.3 to 5.7 and the detection limit of 0.4 µM (S/N = 3). The CNPs modified electrode was successfully applied for fluoxetine determination in capsules and the results showed sufficient precision and achieved a mean recovery accuracy of 99.06%.