جستجوی مقالات مرتبط با کلیدواژه « determination » در نشریات گروه « شیمی »

In the present study, a Glassy Carbon Electrode (GCE) was modified with a nanocomposite of Multi-Walled Carbon NanoTubes (MWCNTs) and β -cyclodextrin (CD) and then decorated with gold nanoparticles to achieve the AuNPs- MWCNTs@β-CD/GCE electrode. The AuNPs- MWCNTs@β-CD/GCE electrode was distinguished via field emission scanning electron microscopy (FE- SEM) and cyclic voltammetry (CV). On the one hand, Interaction between MWCNTs and β-CD increased electro-active surface area. On the other hand, decorating AuNPs on MWCNTs@β-CD caused excellent electrical conductivity modified electrode. Further, the synergistic effect between MWCNTs@β-CD and AuNPs notably increments DP oxidation. Differential pulse voltammetry (DPV) was utilized as a method to determine the amount of dopamine (DP). Using the AuNPs-MWCNTs@β-CD/GCE electrode led to a 26-fold increase in the DP current response compared to the untreated electrode. Under the optimized situation, the prepared sensor exhibited good sensitivity for detection DP in two linear ranges of 3.0–26.0 and 32.0–270.0 μM, with a detection limit of 0.85 μM.

Iron oxide nanoparticles have been widely used in various fields of study. Due to the increasing use of these nanoparticles, it is important to develop sensitive methods for measuring these nanoparticles in real samples. In this research, a method was developed to measure magnetite nanoparticles using microfluidics science and paired emitter-detector diode-based photometry. The basis work of the designed system is based on the magnetic preconcentration of nanoparticles inside the microchip, dissolution by acid, and creation of a signal through the formation of an iron-thiocyanate complex. The validation results of the method showed that the linear range of the method is from 1.0 to 6.0 ppm with appropriate accuracy (recovery percentages: 104.0% and 95.6%) and precision (coefficient of variation: 0.17% and 0.15%), which is satisfactory for measuring trace amounts of magnetic nanoparticles. The limits of detection and quantification were obtained as 0.3 and 0.9 ppm, respectively. Compared to previously reported methods, the developed method provides higher sensitivity and simpler instrumentation of lower analysis cost by the use microfluidic chip for magnetic preconcentration of magnetic nanoparticles, washing, dissolution, and photometric determination.

Sulfide ions in the solution of the Bayer process can accelerate the corrosion of the equipment and increase the impurity of the final product. In the current investigation, sulfide ions concentration of the aluminate solution during the Bayer process was determined using an indirect and inexpensive method. The method did not require any advanced apparatus, which made it suitable for sulfide concentrations over the range of 0.001-1 g/L. To investigate the source of sulfide ions in the aluminate solution, the chemical composition and crystalline structure of the bauxite used to produce alumina were characterized via XRF, XRD, and SEM analyses. The results demonstrated that the main source of sulfide ions was pyrite in bauxite. The advantages and disadvantages of sulfide removal method by nitrate from aluminate solution were investigated. Thermodynamically, the spontaneity of different half-reactions during the reduction of NO3- and oxidation of S2- was studied. Finally, a technique was proposed for the removal of sulfide ions in the aluminate solution by adding nitrate. Moreover, the effect of nitrate concentration on lowering of sulfide ions concentration was evaluated in practical conditions of the bauxite digestion during the Bayer process. The results demonstrated that in conditions of bauxite digestion (at 270 °C, 52 bar, and 60 minutes) by adding 2.5 g/L nitrate ions, the majority of sulfide ions (more than 96%) were eliminated and their undesirable effects were prevented.

The interaction of acetaminophen drug by chitosan-capped gold Nanoparticles was investigated using a resonance Rayleigh scattering (RRS) spectroscopic technique. The standard deviation of (1.1 %), and detection limit of the method (0.5 ng mL-1 in time 6 min, 325 nm) were obtained for sensor level response chitosan-capped AuNPs with (97%) confidence evaluated. The results indicated that this method had good selectivity in the presence of coexisting compounds. The scattering intensity (ΔIRRS) was linearly dependent on acetaminophen drug concentration over the range (0.5 to 200.0 ng mL-1) with a determination coefficient (r) of 0.998. This method could be suitably used for analysis of acetaminophen drug in pharmaceutical, human fluid, and other drugs, and hospital samples.

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.

Tartrazine is a synthetic organic food dye that can be found in common food products such as bakery products, dairy products, candies, and beverage. The presence and content of tartrazine color must be controlled in food products due to their potential harmfulness to human beings.To determine the tartrazine color in solution, we used a prepared from Starch-capped ZnSNPs sensor and kinetic spectrophotometric method. The calibration curve was linear in the range of 0.01 to 10.0 mg L-1. The standard deviation of 1.0 %, and detection limit of the method (0.01 mg L-1 in time 25 min, 399 nm) were obtained for sensor level response Starch-capped ZnSNPs with (95%) confidence evaluated. The chemical Starch-capped ZnSNPs sensor made it possible as an excellent sensor with reproducibility.

A simple, sensitive method for simultaneous quantifying of lisinopril in the presence of losartan in its pure form and pharmaceutical formulations in tablet form by using UV-Vis spectrophotometric. This method depends on the first spectrum derivative utilization zero intersection, the summit to foundation line, and the summit of area measurement. A Linearity was used for a range of drugs, lisinopril concentrations 2-16 µg/mL and losartan concentrations 2-14 µg/mL in the mixture. The correlation coefficients of lisinopril in the presence of losartan (8 μg/mL) using peak to baseline 0.9980, 0.99674, and peak area 0.99944 but the correlation coefficients of losartan in the presence of lisinopril 6 μg/mL utilization peak to baseline 0.9997, 0.9984, 0.9994 and peak area 0.9972, 0.9952. The limits of detection (LOD) of 0.0125 µg/mL for lisinopril and losartan were measured by this method. Determination of precision and accuracy by measuring Relative Standard Deviation (RSD %) whose value is less than 4 % and Recovery% (Rec. %) of acceptable value. The method showed success in the direct estimation of each of the two drugs, lisinopril and losartan, in the presence of the other in pure form and pharmaceutical formulations in tablet form.

In this study, a molecularly imprinted polymers-solid phase extraction-liquid chromatography method to isolate megestrol drug in human fluid samples. The molecularly imprinted polymers using methacrylic acid as the functional monomer and ethylene glycol dimethacrylate as the crosslinking monomer, and 2, 2-Azoisobutyronitrile as an initiator for polymer preparation. To evaluate the applicability of the molecularly imprinted polymers was used as a selective sorbent, general parameters: pH, the amount of solvents, washing solution, and eluent, and time, were optimized following a step-by-step approach. Under the optimum conditions, the detection limit linear range was obtained (0.02 to 2.0 µgL-1). The relative standard deviation of (± 2.0 %), and the detection limit of the method (0.02 µg/L) were obtained. The recoveries up to approximately 97.0 % from spiked human fluid samples could be obtained. The maximum adsorption capacity for the determination of megestrol drugs was 6.8 mgg-1. The proposed molecularly imprinted polymers-solid phase extraction-liquid chromatography method could be applied to the direct determination of megestrol drugs in human fluid samples.

Light-emitting diodes (LEDs) can be used in paired emitter-detector diodes (PEDD) optical sensors as both the light source and the detector. PEDD-based photometers provide low fabrication cost, low power consumption, ease of miniaturization, and a high signal-noise ratio response in a wide wavelength range. This paper reports on developing a cheap but efficient PEDD-based photometer. The photometer consists of a white LED as the emitter diode, an RGB LED as the detector diode (for the first time), and a multimeter for recoding the signal. The developed PEDD-based photometer was utilized for the determination of 2,4,6-trinitrotoluene (TNT) in soil samples. A Meisenheimer complex of TNT with NaOH in acetonitrile was used as a probe to monitor the presence of residual TNT in soil samples. The calibration curve in the soil sample was linear in the concentration range of 0.86 to 110 µg g-1, with a detection limit of 0.27 µg g-1 and a quantification limit of 0.81 µg g-1. Analysis of the soil samples collected from the Iran Cinema and Television Town using the developed method showed trace residual of TNT.

The environmental pollution caused by drug antibiotic waste presents a foremost concern in the ecosystem, as  high  levels  of  these  antibiotic  drugs  after  consumption  when  released  into  the  ecosystem,  biological samples  are  accumulated  and  are  producing  overall  contamination.  Consequently,  the  need  for  selective, sensitive, fast, easy-to-handle, and low-cost early monitoring detection systems is growing. In this study, we used a prepared Albizia Lebbeck Leaves-capped AgNPs sensor to illustrate examples of friendly biosensors with  their  real  application  fields for  the  sensitive  detection  of the  metronidazole  drug  in  various  matrices such as human fluids by kinetic spectrophotometric method. The calibration curve was linear in the range of (0.02 to 10.0 µg L−1). The standard deviation of less than (3%), and detection limits (3S/m) of the method (0.02 µg L−1in time 8 min, 367 nm) were obtained for sensor level response Albizia Lebbeck Leaves-capped AgNPs with (95%) confidence evaluated. The artificial neural network model was used as a tool very low for determining  mean  square  error  (MSE  0.061)  for  metronidazole  drug  by Albizia  Lebbeck  Leaves-capped AgNPs sensor. The observed outcomes confirmed the suitability of recovery and a very low detection limit for  measuring  the  metronidazole  drug.  The  method  introduced  to  measure  metronidazole  drugs  in  real samples  such  as  urine  and  blood  was  used  and  can  be  used  for  other  drugs  environmental  pollution  and hospital samples.

Determination of palladium (II) in traces is significant due to its widespread applications in various fields, especially as alloys in ornaments, electrical appliances and significantly as a catalyst for various synthetic reactions in chemistry. Determination is additionally vital due to the hazardous ecological impacts of the element on biological networks. Thus, attributable to the cordial and poisonous nature of the element, there has been an extensive interest in the detection and determination of its content in various natural and industrial samples. Numerous analytical techniques are accounted for analysis of the metal ion. However, UV-Visible spectrophotometry has been much favorable because of its simplicity, rapidity, inexpensiveness, sensitivity, selectivity, and precision. The present article refreshes ongoing advancements for analysis of Pd (II) spectrophotometrically and fundamental states of the technique required for micro determination of elements in the samples of analytical interest.

An efficient electrocatalyst was developed based on silver nanoparticles/multi walled carbon nanotubes nanocomposite modified glassy carbon electrode (AgNPs/MWCNTs/GCE) by controlled electrodeposition and continuous double-potential pulses to test the high explosive cyclotetramethylene-tetranitramine (HMX) using cyclic voltammetry method. The electrochemical behavior of the system in various pHs was studied by cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), chronoamperometry and chronocoulometry; and some reduction parameters, including the transfer coefficient (α), electron transfer number, apparent electron transfer rate, and diffusion coefficient constants of HMX were estimated. The results demonstrated that reduction of HMX by adsorptive stripping voltammetry on AgNPs/MWCNTs film could remarkably be enhanced and catalyzed compared to bare carbon nanotubes electrode, and the reduction potential could be facilitated from -0.7 V (vs. SCE) to -0.3 V, with electron exchange rate constant of 1.12±0.1 s-1 and 0.17 ±0.1 s-1 for AgNPs/MWCNTs and bare MWCNTs electrodes. Chronoamperometry studies showed a diffusion-controlled process with an apparent diffusion coefficient of 2.01×10−4 cm2 s−1 and a catalytic rate constant of 7.48 times higher than that of bare MWCNTs electrode. Also, chronocoulometric studies showed that the number of electrons transferred for electrochemical reduction of HMX was near 1.98. Under optimized conditions, the reduction peak had two linear dynamic ranges of 2.0-30.0 and 30.0-120.0 mM with the experimental detection limit of 0.2 mM and precision of <2.5% (RSD for five analyses). This modified electrode can be properly used to determine HMX in soil and groundwater samples with satisfactory results.

In this research, a reversed phase high performance liquid chromatographic method was developed for the simultaneous determination of two tyrosine kinase inhibitors, nilotinib and sorafenib. Separation was performed on an Agilent C18 column (4.6×250 mm, 5µm) with mobile phase composition of potassium dihydrogen phosphate buffer (25 mM, pH 4.2) and acetonitrile (35:65 v/v) at 1.2 mL/min with UV detection at 265 nm. Specificity, linearity, precision, accuracy, and robustness of the proposed method were all assessed. Nilotinib and sorafenib had estimated retention times of 5.1 and 5.9 minutes, respectively. Linear concentration ranges for nilotinib and sorafenib, were determined as 0.05-1 µg/mL and 10-45 µg/mL with comparable coefficient correlations (0.999). For nilotinib and sorafenib, the limits of detection (LOD) were determined as 0.030 and 0.020 µg/mL, while the limits of quantification (LOQ) were 0.101 and 0.069 µg/mL respectively.

This study aimed at preparing a Carbon Ionic Liquid Electrode (CILE) modified with a new composite of Multi-Walled Carbon Nano-Tubes (MWCNTs) and TiO2 nanoparticles for AC determination. The proposed electrode was made of a Carbon Paste Electrode (CPE) modified with TiO2 Nano-Particle (NP)-decorated MWCNTs and a binder of IL 1-hexyl-pyridinium hexafluorophosphate (HPFP) (MWCNT/TiO2/CILE). The nanocomposite structure characterization was done via X-ray Energy-Dispersive Spectroscopy (EDS) and Field-Emission Scanning Electron Microscopy (FESEM). The electrochemical behavior of Ac was investigated via the Cyclic Voltammetry (CV) technique at the MWCNT/TiO2/CILE. The MWCNT/TiO2/CILE was applied for Ac determination by Square-Wave Voltammetry (SWV) technique in real samples. The excellent electrocatalytic activity of the proposed nanocomposite leading to Ac electrochemical oxidation in phosphate buffer solution (pH 6.0) was evidenced. The results of Square-Wave Voltammetry (SWV) revealed a wide linear range of 0.01-30 µM and the detection limits of 0.003 µM for the modified electrode under optimal conditions. This electrode was successfully employed to detect Ac concentrations in plasma and tablet samples with good repeatability and reproducibility

Donepezil hydrochloride (DPH), an indan and piperidine derivative, is a selective medicament of Alzheimer’s disease. Two highly selective and eco-friendly membrane based sensors have been designed to determine DPH. Sodium tetraphenyl boron (STPB) and sodium phosphotungestate (SPT) have been used as ion-exchangers, for construction of Sensors 1 and 2, respectively, with β-cyclodextrin (β-CD) as ionophore and nitrophenyl octyl ether (NPOE) as a plasticizer. The sensors are highly capable to determine DPH of linear concentration range 1.0 × 10-6 to 8.0 × 10-3 M at the pH ranged between 5 and 8. The Nernstian slopes of 58.51±0.80 and 57.16±0.67, for Sensor 1 and 2, respectively, reflected the appropriate functioning of electrode sensors in relative to concentration of DPH. The limits of detections (LOD) for both the sensors have also been reported. The results from validation of both the sensors reflected high selectivity for measuring potential of DPH solutions. Sensors have been subjected to validity check through accuracy, precision, robustness and ruggedness. Specific functioning of Sensor 1 and 2 permitted to achieve 99.26% as mean recovery of DPH from tablets analyses. The outcome of statistical tests between the results from sensors 1 and 2 with reference method pronounced the extraordinary applicability of the methods to determine DPH in pharmaceuticals. These methods are greener approaches due to the non-usage of any organic toxic solvent and pre-treatment and extraction steps’ absence.

In this study, a simple and fast colorimetric assay based on the aggregation of gold nanoparticles (AuNPs) was achieved for the determination of μg/Lof tolyl triazole (TTA). The aggregation of AuNPs is due to the high affinity between gold surface and nitrogen atoms of TTA and intermolecular bonding formation between TTA molecules. The plasmon peak of AuNPs at 520 nm was decreased with the formation of a band about 620 nm owing to the aggregation phenomenon. The effective parameters on the peak shift such as ionic strength, pH of the sample, and AuNPs concentration was investigated. The proposed method is capable of determining TTA over a concentration range of 10-100 µg/L with a limit of detection of 5.0 µg L-1 based on the absorbance ratio at 620 nm to 520 nm. The relative standard deviation of the method was 3.0% and 1.5% for 20 and 80 µg/L, respectively. A comparison between the outlined method and the previously published methods for TTA determination has also been made. The obtained results from this study proved to be effectively successful in the determination of TTA in water.

Megestrol drug is a synthetic steroid progesterone, and it is used as an anti-plasma agent to treat advanced breast cancer or endometriosis. Although the liquid chromatographic method for measuring megestrol has advantages such as excellent accuracy and reproducibility, it has limitations such as long-time measure, high equipment cost, and maintenance and use. In this study, for determination of megestrol drug in solution using kinetic spectrophotometric method, we prepared a solution of Albizia Lebbeck Leaves-capped AgNPs utilizing sodium borohydride as a stabilizer sensor. The calibration curve was linear in the range of (0.1 to 10.0 µg L−1). The standard deviation of (3.0%), and detection limit of the method (0.2 µg L−1 in time 7 min, 385 nm) were obtained for Sensor level response Albizia Lebbeck Leaves-capped AgNPs with (95%) confidence evaluated. The observed outcomes confirmed the suitability recovery and a very low detection limit for measuring the megestrol drug. The method introduced to measure megestrol drug in real samples such as urine and blood was used and can be used for hospital samples. The chemical Albizia Lebbeck Leaves-capped AgNPs sensor made it possible as an excellent sensor with reproducibility.

Sensor synthesis synthesized PbS functionalized with gelatin quantum dots have been considered as novel drugs sensors due to their ultrafine size, photo-stability and excellent fluorescent properties. In this study, a facile method was developed for the preparation of fluorescent water-soluble PbS quantum dots with gelatin sensor. The fluorescence of the PbS quantum dots sensor functionalized with gelatin synthesis is selectively and sensitively enhanced by addition of the Phenylpropanolamine (PPA) drug-induced aggregation of sensor PbS with gelatin. This finding was further used to design a fluorometric method for the determination of (PPA) drug, The reaction is followed fluoremetrically by measuring the absorbance at 335 nm. 2.5×10-2 molL-1 PbS with gelatin sensor, calibration graph in the rang of 0.05 - 10.0 µg L-1 (PPA) drug. The absorbance is linear from 0.05 up to 100.0 µg L−1 in aqueous solution with repeatability (RSD) of 3.5% at a concentration of 10.0 µg L−1 and a detection limit of 2.2 µg L−1 by the fixed-time method of 60 sec. The relative standard deviation for 10.0 µg L-1 (PPA) drug is %95. The applicability of the method was demonstrated by the determination of the (PPA) drug in urine and blood samples