Iranian Journal of Analytical Chemistry
Volume:10 Issue: 2, Summer and Autumn 2023

The principle of this research is based on the development of multi-residue method by QuEChERS sample preparation follow by gas chromatography with mass spectrometric detection in the selected ion monitoring mode (GC–MS-SIM) for the routine analysis of 42 pesticides in rice samples. The rice samples were initially extracted with acetonitrile, and the targeted pesticides were purified following the dispersive solid phase extraction (d-SPE) cleanup method. The calibration curve for each analyte quantified by matrix-matched calibration was linear over the concentration range of 10.0–1000.0 μg L−1 with a correlation coefficient range between 0.990 and 0.999. Mean recoveries from three replicates ranged from 79% to 112%, with satisfactory precision (RSD<7%). The limit of detection and the limit of quantification were in the range of 3.04–12.52 μg L−1 and 10.14–41.76 μg L−1 respectively, for all 42 pesticides.

Microorganisms create metal nanoparticles (MNPs) after being exposed to toxic metal ions. Nevertheless, the catalytic performance of biosynthesized MNPs has not been investigated in spite of the possibility of utilizing these biological processes in the stable improvement of vital metals (e.g. zinc oxide). This strategy has excellent advantages like high economic efficiency and tolerance of functional groups. DaZnO NPs characteristics were recognized by numerous techniques, including FT-IR, SEM, TEM, XRD, and EDS analyses. In this study, biogenic zinc oxide nanoparticles were produced by the Desulfovibrio alaskensis to reduce carbon dioxide for the preparation of formate salts in an aqueous medium.

In this research, Fe3O4, Fe3O4/polystyrene and Fe3O4/polyaniline nanocompounds were prepared and compared on the removal of methyl orange from aqueous solutions. The chemical structures of the synthesized compounds were studied using FT-IR. The crystalline phase of Fe3O4, Fe3O4/polystyrene and Fe3O4/polyaniline nanocompounds was characterized by XRD. SEM was used for detecting morphology of the synthesized samples. The magnetic property of the prepared samples was successfully checked. The prepared nanocompounds were used to remove methyl orange as an anionic dye from aqueous solutions. Based on results, Fe3O4/polyaniline nanocomposite showed higher efficiency in the removal of methyl orange, which is partly due to the oppositely charged methyl orange and Fe3O4/polyaniline. Effective variables on the removal of methyl orange such as adsorbent dosage, pH,  and contact time were studied and optimized. At the optimum situations the pH, catalyst dosage, and time were 3-4, 450 mg L-1, and 50 min, respectively. For detecting the type of adsorption isotherm, Langmuir, Freundlich, and Dubinin Radushkevich adsorption isotherms were studied. According to Langmuir model, Fe3O4/polyaniline magnetic absorbent showed the highest methyl orange adsorption capacity of 48.76 mg g−1. Kinetic studies proved that methyl orange adsorption was explained more accurately via pseudo-second order model compared to the pseudo-first order model. Under controlled reaction conditions, Gibbs free energy (ΔG˚) varied from -1.41 to -1.69 kJ mol-1, besides, the resulting ΔH˚ and ΔS˚ quantities were obtained 4.07 kJ mol-1 and 0.018 kJ mol-1K-1, respectively. Therefore, it can be considered that the adsorption of methyl orange  onto the Fe3O4/polyaniline magnetic absorbent is a spontaneous and endothermic procedure.

In the present work, an efficient method was developed for the determination of lead in natural water samples. In this method, lead was extracted by octanoic acid reverse micelles (bulk phase) and measured by flame atomic absorption spectroscopy (FAAS). Ligand 1-(2-Pyridylazo)-2-naphthol was used as a chelating agent. In order to obtain the best extraction results, some experimental parameters (such as pH, ligand concentration, ionic strength, etc.) affecting the extraction efficiency were investigated and optimized. Under optimal conditions, the calibration curve was linear in the concentration range of 2.5-200.0 μgL-1 with a correlation coefficient of 0.9998. The detection limit was 0.8 μgL-1 and the preconcentration factor was 50. This method was successfully used to measure lead in natural water samples.

Contamination of water sources with chromium has become a pervasive global problem due to its wide use in industry. In this research, low-cost commercial sodium bentonite and synthesized nano bentonite were used to remove chromium ions from aqueous solutions along with electro thermal atomic absorption spectroscopy (ETAAS) and Ultraviolet-Visible Spectrophotometry (UV-Vis) were used. The morphology of the bentonite samples was studied using XRD, FTIR and scanning electron microscope (SEM) analyzes. To screen the relative importance of variables, parameters including pH, adsorption time, amount of adsorbent, volume of desorption solvent and stirring speed were studied using the Plackett Burman Design (PBD) using the Minitab 20 software. In the following, optimization was performed by using the central composite design (CCD), and the responses were evaluated. The calibration curve was plotted by drawing the absorbance against standard concentration. The linear dynamic range of 0.003-100 μg L-1 (DLR) and the correlation coefficient (R2) of 0.999 were obtained for chromium. Limit of detection (LOD) and limit of quantification (LOQ) for chromium were obtained equal to 0.002 and 0.0039 μg L-1, respectively. The relative standard deviation (RSD) of 6.93% and the relative recovery for chromium in real samples were obtained in the range 96.041% to 103.445% for ETAAS method. The values of detection limit (LOD) and limit of quantification (LOQ) by UV-Vis method were 0.007 and 0.021 µg L-1 respectively, and the dynamic linear range was (DLR) 0.05-50.00 µg L-1 with a correlation coefficient (R2) 0.998. The relative standard deviation (RSD) was 14.27% and the relative recovery of this method in real samples was attained from 95.103% to 103.692%.

The work is a feasible study about the performance of woody skin and outer soft shell of Hazelnut for the removal of lead ions from water. The Hazelnut woody skin and soft outer shell are crushed by an innovative ball mill to prepare micro and nano powders. TEM images show that the produced nano powder includes uniform nanoparticles with 8-10 nm average diameters. The produced nanoparticles were used as a suitable and effective biosorbent to remove lead ions from water. Experimental data shows that the adsorption of lead ions on the surface of hazelnut skin nanoparticles is acceptably fitted to Langmuir isotherm model. Based on the Langmuir isotherm, a maximum adsorption capacity of 91 mg g-1 is achieved for adsorption of lead ions on the surface of hazelnut skin nanoparticles. The obtained results showed that the best removal of lead ions can be done under conditions includes 50 ml initial solution, pH=4, 120 mg L-1 initial concentration of lead ions per 70 mg biosorbent for contact time of 20 minutes at room temperature. The adsorbed ions are easily eluted by 1.5 ml 0.7 M HNO3 solution. Under the optimal conditions, preconcentration factor of 200, %RSD of less than 5% with detection limit of 100 ppb are obtained. The effects of some interfering ions such as Fe2+, Cu2+, Mg2+, Zn2+, Mn2+ and Ni2+  on the removal efficiency of lead ions were studied. The presented method is successfully applied for removal and determination of lead ions from real samples.

A head space solid-phase microextraction (HS-SPME) method coupled to gas chromatography/mass spectrometry (GC/MS) has been developed and applied for profiling of volatile compounds released from Ocimum sanctum L.  during plant growth. Three types of different SPME fibers including polydimethylsiloxane (PDMS) ,divinylbenzene /carboxen /polydimethylsiloxane (DVB/CAR/PDMS) ,carboxen /polydimethylsiloxane (CAR/PDMS) and carbowax/polyethylene glycol (CW/PEG) were used as an adsorption phase and the best extraction was achieved with the mixed fiber 2.  A gas chromatography coupled with mass spectrometer was employed for identification of the volatiles extracted from the head space of sampling vials by SPME. As a result, 23 compounds were detected using this method. Esdragol (70.33-90.57%), L-carrol ( 0.07-4.66%), α-citral (0.28-6.76%), caryophyllene ( 0.33-2.12%), β-citral (0.14-9.63%) and methyl eugenol (0.33-3.11%) were dominate volatile components, the relative content of which was found to enable differentiating between the seasonal examined. The oxygenated terpens were the most aroma compounds of O. sanctum L. in head space of the  sample vial.

In this study, a novel mixed ligand (Dithizone-Co(II)-Alizarin red S: DTZ-Co-ALR-) ensemble is designed and developed ultra-sensitive, and highly selective to UV-Vis absorption and for naked-eye detection of Arginine (Arg), and Glutathione (GSH). The out coming high sensitivity and selectivity for new receptor (DTZ-Co(II)-ALRs-Arg) was attained by adding Glutathione. The indicator is released due to its displacement from the mixed ligand (DTZ-Co-ALRs-Arg) by Glutathione and the change in absorbance may be due to the further complexation of GSH with the additional coordination sites present in the Arg bonded with the mixed ligand (DTZ-Co-ALRs). The label-free DTZ-Co-ALRs receptor provided sensitive and selective detection of L-Arginine, and Glutathione with detection limits of 0.03, and 0.009µmol L-1, respectively. The protocol especially offers high selectivity for the determination of Arg, and GSH among amino acids found in real samples. Moreover, the investigation of the logic behavior of the proposed DTZ-Co-ALRs receptor indicated its capability of functioning as an INHIBIT-type colorimetric chemosensor with the chemical inputs and UV-Vis absorbance signal as the output. This mixed ligand receptor could also behave as a molecular “keypad lock” with the correct sequential addition of Arg and GSH inputs.

Addressed herein, Bismuth sulfide (Bi2S3) as a synthetic semiconductor chalcogenide applied in fabrication process of an aptasensor as a signal promoter for ultra-trace detection of aflatoxin B1(AFB1). The analytical signal was improved by using optimized amounts of Bi2S3 for electrode modification. The AFB1 Aptamer single strand type(SSDNA) was simply immobilized on the cross section of a pencil lead through polydopamine layers. A wide concentration range of trace amounts of AFB1(0.3-630nM) was supported by the fabricated aptasensor (pencil/polydopamine@Bi2S3/aptamer) using differential pulse voltammetry. Simple fabrication and no needing to electrode refreshment were part of the advantages of the suggested aptasensor. Finally, very low resulted detection limit(0.04nM) with a great sensitivity (0.076µA/nM) and also appropriate stability and repeatability led to application of the aptasensor in real sample analysis such as wheat flour with brilliant recovery percentages.

In this study, iron oxide/cellulose acetate nanocomposite was prepared by electrospinning method and its performance was evaluated for removal of arsenic. Here, oleic acid coated magnetite nanoparticle was synthesized by co-precipitation method and was impregnated in cellulose acetate solution. This magnetite impregnated polymer solution, was electrospun to form nanocomposite polymer fiber. The cellulose acetate/iron oxide nanocomposite membrane was characterized by SEM and FTIR. The magnetic properties of composite nanofibers were characterized by using vibrational sample magnetometry analysis. The nanocomposite was used to remove arsenic ions from aqueous solution. Batch adsorption experiments were carried out to study the sorption behavior of arsenic ions as a function of pH, contact time and initial concentration. Experimental results showed that the maximum capacity of the cellulose acetate-iron oxide nanocomposite membrane for removal of arsenic from low concentration is 0.36 mg/g at pH 9. For better investigation of the adsorption mechanism, two isotherm models, Langmuir and Freundlich were tested. Based on the isothermal results, adsorption data were fitted well to Langmuir isotherm. The reusability of the nanocomposite membrane was confirmed for several adsorption and desorption processes by acid-alkali treatment.

In this work, sub-micro and nanometer sized Mg and Mg/carbon composites as anode materials of Mg-air batteries is prepared by using an innovative rotary ball mill. Characterization of the prepared samples is performed by dynamic light scattering, scanning electron microscopy, transmission electron microscopy and, X-ray diffraction techniques. The effects of milling time and amount of carbon additive are evaluated on the sizes of Mg particles in different samples, the discharge capacities and also other electrochemical performances of both primary and secondary magnesium air batteries. An aqueous solution of 2 M Magnesium Chloride and 3 M Sodium Chloride and an organic solution of 0.2 M I2 in Dimethyl Sulfoxide are used as electrolytes in primary and secondary Mg-air batteries, respectively. The Mg sample T6 with average particle size of 170 nm and the Mg/carbon composite sample T13 with average particle size of 35 nm show the highest discharge capacities in both primary (333.1 and 418.6 mA.h g-1) and secondary (354.4 and 433.9 mA.h g-1) Mg-air batteries, respectively. The cycle life test was examined on all constructed rechargeable Mg-air batteries over 30 cycles.

The rapid expansion of a supercritical solution (RESS) process has limited commercial applicability due to the extremely low solubility of polar drugs in supercritical CO2 (sc CO2). To overcome this major limitation, a modified process of rapid expansion of supercritical solution with solid cosolvent (RESS-SC) is proposed. Here, the RESS-SC is examined for clozapine using menthol solid as a cosolvent to reduce particle size and to increase drug solubility. In addition, the effect of extraction pressure and extraction temperature was investigated on the size and morphology of precipitated particles of clozapine. The properties of the micronized clozapine were assessed using scanning electron microscopy (SEM) and powder x-ray diffraction (XRD) techniques. In this study, the average particle size of clozapine was reduced from 29.15 (before RESS-SC) to 3.15 μm (after RESS-SC).

In this research, the results of two existing methods for synthesizing gold nanoparticles, i.e., the green and environment-friendly method and the usual chemical method called Turkovich, were compared and analyzed. In the green method, the extract of the aerial parts of the medicinal plant Mentha pulegium was used as a regenerating agent, and both methods, SEM, TEM, UV-VIS, EDX, and DLS, investigated the properties of the synthesized gold nanoparticles. The results indicated that the green synthesis of gold nanoparticles by extracting the aerial parts of the Mentha pulegium plant was smaller and more stable than the Turkevich method. SEM and TEM results show that the morphology of all nanoparticles is spherical. The size of nanoparticles synthesized by sodium citrate is 10.3 nm, and the size of nanoparticles synthesized by Mentha pulegium plant extract is 9.6 nm. The UV-VIS results show almost absorption in the region of 526 nm for gold nanoparticles synthesized by sodium citrate and absorption in the region of 421 nm for gold nanoparticles synthesized by Mentha pulegium plant extract. The synthesized gold nanoparticles had antibacterial activity against different bacteria.

Measuring preservative concentrations in food is crucial due to their potential health implications. Therefore, it is necessary to develop a reliable and validated analytical method for monitoring. This study focuses on the validation of a simple, sensitive and precise analytical approach using HPLC-DAD to concurrently assess sodium benzoate and potassium sorbate. The validation process resulted in exceptional outcomes, demonstrating strong linearity (R2 > 0.999), precision (RSD < 5%), and accuracy (recovery values ranging from 90.77% to 100.55%). Additionally, the method exhibited low limits of detection and quantification (0.8 and 2.65 mg L-1 for sodium benzoate, and 0.14 and 0.47 mg L-1 for potassium sorbate, respectively). The effectiveness of the validated method on different food metrics was shown by analyzing 110 samples of Olivier salad, dairy products and ketchup sauce from Mashhad, Iran. Comparison of the results with Iran's national standards revealed that the preservative concentrations in most samples were within the acceptable limits set by Iranian regulations.

The use of additives is a standard method in both electrowinning and electrorefining of copper. They have multiple roles in the electrodeposition of copper. They are diffusion barriers and/or complexing agents for copper. In addition, they can perform other important roles as well. Thiourea has been extensively used as an additive in industrial copper electrorefining processes. The effect of thiourea on anode passivation, nodule formation in the cathode, and polarization of copper reduction has been investigated. In this study, we reviewed the most important studies conducted on the mechanism of thiourea effect in the copper electrorefining process, as well as the methods of determination and monitoring thiourea in real samples of copper refinery.