Iranian Journal of Analytical Chemistry
Volume:4 Issue: 1, Winter and Spring 2017

A solid phase extraction method based on new functionalized silica gel sorbent for the preconcentration and determination of trace mercury (II) ions by cold vapor atomic absorption spectrometry (CV- AAS) was developed. The effective parameters on mercury extraction were optimized using two optimization methods fractional factorial design and central composite design. Various factors affecting the recovery of the analyte were investigated using batch equilibrium technique. The best eluent for desorption of mercury was 5 mL of 0.1 M thiourea. Many anions and cations were examined in interference studies and the method shows very high selectivity for determination of mercury in presence of other species. Under the optimum conditions, the analytical curve was found to be linear in the range of 10- 1600 ng L-1 with a detection limit of 2.3 ng L-1. The method was successfully applied to determination of mercury in tap, river, sea water, urine and fish samples with good spike recoveries. The obtained results were in accordance with electrothermal atomic absorption spectrometric method. Student’s t-test indicated the validity and accuracy of the proposed method for analysis of mercury in real samples.

A new pyridine derivative ligand, (E)-(Pyridine-2-ylmethylidene)({2-(E)-(Pyridine-2-ylmethylidene)amino]ethyl}has been synthesized and kf value of its complexes with Cu2+, Ni2+, Cd2+, Zn2+, Hg2+ and Co2+has been determined by spectrophotometric and conductometric methods in acetonitrile at various temperatures. The formation constants (Kß = K1 × K2) of the 1:1 and 1:2 (metal ion to ligand) complexes were calculated by computer fitting of the absorbance-mole ratio data, and molar conductance-mole ratio data at different temperatures, and   found that complexes to vary in acetonitrile solvent in the order of Cu2+ >Hg2+>Zn2+>Co2+> Cd2+> Ni2+>Ag+. The enthalpy and entropy changes of the complexation reaction were evaluated from the temperature dependence of formation constants.

In this study, an oral insulin delivery system, based on Biocompatible and smart pH sensitive Hydrogel (PSH) on to natural polymer nano-cellulose backbones has been designed. PSH is made of mixed acrylic acid and 2-hydroxyethyl methacrylate on the nano-cellulose backbones and has been identified by using FT-IR and SEM methods. Synthetic networks, can sense the pH environment changes and lead to the creation of a swinging distribution pattern. The results show that the main factor influencing the behavior of the hydrogels in drug distribution, is the pH environment, so that the rate of drug release from the hydrogel, within 48 hours in a simulated body environment in SIF with pH= 9 and blood plasma-neutral environment with pH= 7.4, (93%) has been in greater amount of  it’s release in acidic conditions  (SGF with pH= 1.5) and the results have been satisfactory for the preparation of oral insulin.

In this study, vortex-assisted low density based dispersive liquid-liquid microextraction followed by high performance liquid chromatography with ultraviolet detector has been developed for the determination of three pesticides including chlorflurenol-methyl, chlorfenvinphos, and diazinon from environmental water samples. Different parameters influencing the extraction efficiency such as the type and volume of extraction and disperser solvent, sample pH, salt addition as well as vortex and centrifugation time were investigated and the optimal conditions were obtained. Under the optimum conditions, the calibration curves were linear in the concentration range of 8.5–100, 3.1–100 and 36.5–600 ng/mL for chlorflurenol-Methyl, chlorfenvinphos and diazinon, respectively, with coefficient of determination (r2) of 0.993 or better. The limits of detection and quantification of the analytes, which were determined at 3 and 10 signal-to-noise ratio (S/N) ranged from 0.9–11 and 3.1–36.8 ng/mL, respectively. The proposed method has been successfully applied to the analysis of real water samples. The relative recoveries (%RR) studied at two spiking concentration levels were ranging from 76–108%, with the corresponding relative standard deviation (%RSD) ranging from 1.9–9.9%.  The results of study demonstrated that the proposed method is efficient for extraction and/or preconcentration of the three pesticides prior to quantitative determination utilizing HPLC–UV/Vis instrument.

In this work, a new method was developed for the catalytic reduction of hydrogen peroxide at glassy carbon electrode modified with silver nanoparticles and multi-wall carbon nanotubes. Silver incorporated in this modified electrode acted as catalyst to reduce hydrogen peroxide. First, the electrochemical behavior of silver, incorporated in modified electrode, was studied. The results illustrated the adsorption-controlled reaction at the modified electrode. Then, the behavior of catalytic reduction of hydrogen peroxide at the modified electrode was investigated. A linear calibration graph was obtained for hydrogen peroxide over the concentration range of 4.04×10−3 – 1.5×10−6 molL-1. The detection limit for hydrogen peroxide was estimated 1.42×10−7 molL-1. The relative standard deviation of ten replicate measurements (performed on a single electrode at hydrogen peroxide concentration of 1.5×10-4  molL−1) was 2.36%. The proposed electrode was used for the determination of hydrogen peroxide in real samples which led to satisfactory results.

A quantitative structure-activity relationship model has been created for forecasting the antagonist potency of benzyl tetrazole derivatives as human histamine receptors. Various kinds of molecular descriptors were used to represent different aspects of the molecular structures. In this method, the whole data set for the compounds were divided into the training and test sets. The model of relationships between molecular descriptors and biological activity of molecules were created by using stepwise multiple linear regressions and a genetic algorithm. Comparison of the results obtained indicated the superiority of the genetic algorithm based multiple linear regression over the stepwise based multiple linear regression. The ultimate quantitative structure-activity relationship model (N =64, R2=0.808, F= 30.806, Q2adj= 0.782, Q2LOO = 0.751, Q2LGO=0.669) was fully approved using the leave-one-out cross-validation method, Fischer statistics (F), external test set and the Y-randomization test. As a result, the produced quantitative structure-activity relationship model could be applied as a valorous instrumentation for sketching analogous groups of new antagonists of histamine receptors.

In this research, an inexpensive and effective method for determination of Isoniazid (INH) is presented by using a poly (Eriochrome black T) modified pencil lead electrode. The potential of modified electrode in electrochemical sensing of INH was evaluated by cyclic voltammetry and hydrodynamic amperometry methods. The overall number of electrons involved in oxidation of INH was fond 4 electrons. The calculate diffusion coefficient for INH was equal to 9.74 × 10-7 cm2/s. Calculated limit of detection for method was 66.0µM and 20.4µM applying cyclic voltammetry and hydrodynamic amperometry methods, subsequently. The ability of prepared electrode for determination of INH in real sample was evaluated by applying the proposed method to human plasma analysis and the results were compared with the standard method, presented by United State Pharmacopeia. Presented method exhibited a satisfying precision (%RSD=4.64). Also the proposed method showed a good accordance with standard method in confidence level of 95%.

A simple, novel, accurate and selective method for the determination of trace amounts of Cu2+ ions in water and soil samples is proposed. The method is based on the separation and preconcentration of Cu2+ on a nano-SiO2 modified by a cetyltrimethylammonium bromide as surfactant and indane-1,2,3-trione-1,2-dioxime as complexing agent. The retained copper on the nano-sorbent was eluted with 1.5 mL of 1.0 mol L-1 HNO3 and measured by flame atomic absorption spectrometry. The synthesis of this nano-sorbent is also described and certified by FTIR, XRD and TEM techniques. Furthermore, several effective analytical parameters were evaluated and optimized. Under the best optimum conditions maximum absorption capacity, enrichment factor and limit of detection were 7.04 mg g-1, 333.3 and 4.4 µg L-1, respectively. The relative standard deviation of the preconcentration method was 0.28% (n=7) and calibration curve gave good level of linearity with correlation coefficient value 0.997. Finally, the feasibility and performance of the method was evaluated by determination of copper (II) ions in several water and soil samples with satisfied results.