Ahmad Soleymanpour

A new carbon paste electrode for rifampicin (RIF) drug was prepared and fully characterized in terms of composition, usable pH range and temperature. The sensor is based on 2-hydroxypropyl β-cyclodextrin as a good ionophore in the carbon paste matrix. The modified electrode showed a Nernstian slope of 59.2 mV/decade over the concentration range of 3.2 × 10−8 to 2.2 × 10−4 M with a limit of detection 2.3 × 10−8 M. The electrode has a short and stable response time of 4 s. The sensor manifested advantages of simple design, low cost, wide concentration range, excellent selectivity to rifampicin, applicable as an indicator electrode and renewability. The sensor was successfully used for determination of rifampicin in tablet and blood serum samples. Temperature dependence of the sensor potential response was examined in the temperature range of 15–55 °C. The sensor showed a very low thermal coefficient within the studied temperature range. © 2018 Elsevier B.V.

A sensitive and fast ultrasound-assisted dispersive liquid-liquid microextraction procedure combined with ion mobility spectrometry has been developed for the simultaneous extraction and determination of bendiocarb and azinphos-ethyl. Experimental parameters affecting the analytical performance of the method were optimized: type and volume of extraction solvent (chloroform, 150 µL), pH (9.0), type and volume of buffer (ammonium buffer pH = 9.0, 4.5 mL) and extraction time (3.0 min). Under optimum conditions, the linearity was found to be in the range of 2–40 and 6–100 ng/mL and the limits of detection (LOD) were 1.04 and 1.31 ng/mL for bendiocarb and azinphos-ethyl, respectively. The method was successfully validated for the analysis of bendiocarb and azinphos-ethyl in different samples such as waters, soil, food and beverage samples. © 2018 Elsevier Inc.

Electrochemical characterization of functionalized carbon nanotubes (f-CNT) including carboxyl (CNT-COOH), amine (CNT-NH2) and hydroxyl (CNT-OH) functional groups were studied using differential pulse voltammetry (DPV). The current-voltage (I-V) curves were obtained from each system and the effect of f-CNT on redox interaction of horseradish peroxidase (HRP) immobilized on the electrode surface was investigated. The non-equilibrium Green's function (NEGF) combined with density functional theory (DFT) were used to study the transport properties of f-CNT. Additionally, the effect of the number of functional groups on transport properties of CNT, I-V characteristics, electronic transmission coefficients and spatial distribution of f-CNTs have been calculated and analyzed. The results showed that the carboxyl derivative has larger transmission coefficients and current value than other f-CNTs. Then, the effect of functional groups on the electron transport in heme group of HRP is discussed. Finally, the effect of a covalent bond between active site amino acids and amine functional group of CNT was investigated and discussed. © 2018 Elsevier Ltd

A simple and rapid solid phase extraction procedure using a mini-column packed with modified sulfur nanoparticles as a new, efficient and reusable sorbent has been developed for the preconcentration of carbamazepine prior to its determination by high performance liquid chromatography. This method is based on the retention of carbamazepine by modified sulfur nanoparticles which are quite efficient for fast adsorption and desorption of carbamazepine. An HPLC system including C18, 250 × 4.6 mm column, methanol-acidic water (pH = 2.6 by acetic acid) (60:40) as mobile phase and UV detector (λ = 276 nm) was used. The effects of multiple experimental conditions such as the effect of pH, type and volume of buffer, type and volume of eluent, sample and eluent flow rate, sorbent amount and interfering ions, on the analytical performance of the method were investigated. The calibration curve was linear in the range of 0.5–200 ng mL−1 and LOD of the proposed method was found to be 0.16 ng mL−1. The procedure was successfully applied for the determination of carbamazepine in pharmaceutical samples, human plasma and breast milk. © 2017 Elsevier B.V.