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New carbon dots derived from caffeine and boric acid were fabricated for “ON–OFF–ON” determination of aluminum and fluoride. Advantages are simplicity, high quantum yield, and low detection limit.

In the present work, a triple amplified biosensor was constructed for ultrasensitive and selective analysis of an acetylcholinesterase inhibitor; rivastigmine (RIV) in human serum. The modified biosensor based on fabrication of pencil graphite electrode (PGE) with lepidocrocite nanoparticles (γ-FeOOH) dispersed in N-chitosan carbon nanosheets (N@CCNS). Pyrrolidinium acid sulfate (PAS) as an ionic liquid was added to amplify the signal of RIV. The physical properties of the modified electrodes were characterized by powder X-ray diffraction (PXRD), Fourier transform infrared spectroscopy (FTIR), scanning electron microscope (SEM) and energy dispersive X-ray (EDX) spectroscopy. The cyclic voltammetry (CV), differential pulse voltammetry (DPV) and electrochemical impedance spectroscopy (EIS) were used to evaluate the performance of the modified electrode. Parameters affecting performance of the modified sensor were evaluated such as pH, scan rate, casting volume, concentration of nanocomposite . . . etc. The modified sensor showed a fast and sensitive electrochemical response to RIV sensing with wide linear range (3.0-90.0 nM), low detection limit (0.99 nM) and excellent anti-interference ability. Moreover, the fabricated sensor was successfully applied for determination of RIV in pharmaceutical tablets and spiked human serum and the obtained results are quite satisfactory.

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The aim of this paper is to develop sensitive, accurate, reproducible and robust RP-HPLC with fluorescence detection for estimation of donepezil (DZ) in rabbit plasma using silodosin as the internal standard (IS). The prepared samples were quantified on reversed phase column Luna C18(2) (150 × 4.6 mm i.d., 5 µm particle size) operated at room temperature using the mobile phase consisting of methanol: 0.1% acetic acid (50 : 50, v/v) at a flow rate of 1 ml min−1. The method was fully validated according to bioanalytical validation guidelines of FDA in terms of system suitability, selectivity, sensitivity, precision and stability. It was found that the increase in peak areas followed the increase of DZ concentration in the range of 2.56–200.00 ng ml−1 with LOD of 0.85 ng ml−1. The method was successfully applied for the determination of DZ in rabbit plasma using manual shaking dispersive liquid–liquid microextraction.