Determination of bupropion by off-line coupling Fe3O4@CuO&GO nanocomposite and ion mobility spectrometry with application to biological samples.

In this study, an off-line coupling of dispersive solid-phase extraction (DSPE) and ion mobility spectrometry (IMS) was introduced to extract and determine bupropion (BUP). A magnetic nanocomposite adsorbent (Fe3O4@CuO&GO) was fabricated by combining graphene oxide (GO) sheets with Fe3O4 and CuO through coprecipitation method. The synthesized adsorbent was characterized and analyzed using the analytical techniques. The effect of extraction parameters including desorption solvent (type and volume), pH, adsorbent amount, contact time, temperature, and the volume of analyte solution on the extraction efficiency was investigated and optimized. The operational parameters of IMS method were also investigated. Under the optimum conditions (DSPE-IMS), the proposed method provided a linear range 4.0-24.0 ng for BUP with a determination coefficient R2 ≥ 0.98. LOD and LOQ values were 0.7 and 2.2 ng for BUP. The repeatability of proposed method was evaluated and reported as relative standard deviation (RSD% ≤ 5.5). The developed method was applied to determine BUP in different biological samples, in which satisfactory results were obtained (93.0-98.0%).

Fabrication of a novel sensor based on Cu quantum dot and SH-SiO2 nanoparticles supported on copper-based metal organic framework (Cu QD-SH-SiO2@Cu-MOF) and its application for the simultaneous determination of norepinephrine, piroxicam and epinephrine.

In this research, a novel electrochemical sensor with excellent sensitivity was fabricated based on Cu quantum dot (Cu QD) and SH-SiO2 nanoparticles immobilized on copper-metal-organic frameworks (Cu-MOFs) for determining piroxicam and simultaneous determination of norepinephrine, piroxicam and epinephrine. The nanoparticles were synthesized and characterized using FT-IR, EDX, FESEM, TEM and BET, and were subsequently used to modify carbon paste electrode. Cu QD-SH-SiO2@Cu-MOF for electrode modification possesses a distinctive structure and a high conductivity that raises the electron transfer rate and enhances the performance of electrochemical sensors. Square wave voltammetry was applied to investigate the redox properties of Cu QD-SH-SiO2@Cu-MOF/CPE, voltammograms showed three distinct anodic peaks at 0.41, 0.62 and 1.06 V in the presence of norepinephrine, piroxicam, and epinephrine. Various experimental parameters including the type and pH of electrolyte and scan rate were investigated. The calibration graph was obtained over the range 0.2-34285.0 µM including three linear segments. Also, the limit of detection was calculated as 0.05 µM of piroxicam. The introduced sensor was satisfactorily utilized for electrochemical determination of norepinephrine, piroxicam, and epinephrine in real samples. The obtained results using the introduced sensor were validated by high-performance liquid chromatography and the statistical tests confirmed the good agreement of them.

A New Sensitive Method for Quantitative Determination of Cisplatin in Biological Samples by Kinetic Spectrophotometry.

This study describes a kinetic spectrophotometric method for accurate, sensitive and rapid determination of cisplatin in biofluids. The developed method is based on the inhibitory effect of cisplatin on the oxidization of Janus Green by bromate in acidic media. The change in absorbance as the criteria of the oxidation reaction was followed spectrophotometrically. To obtain the highest rate of sensitivity, efficient reaction parameters were optimized. Under optimum experimental conditions, a calibration graph was obtained linearly over the range 10.0 - 5750.0 µg L-1 and the limit of detection (3sb/m) was 4.2 µg L-1 of cisplatin. The interfering effect of diverse species was investigated. The developed method was used for the quantification of cisplatin in bio fluids of patients treated with cisplatin, spiked bio fluids and pharmaceutical samples and yielded satisfactory results.

A new sensitive sensor for simultaneous differential pulse voltammetric determination of codeine and acetaminophen using a hydroquinone derivative and multiwall carbon nanotubes carbon paste electrode.

A new sensitive sensor was fabricated for simultaneous determination of codeine and acetaminophen based on 4-hydroxy-2-(triphenylphosphonio)phenolate (HTP) and multiwall carbon nanotubes paste electrode at trace levels. The sensitivity of codeine determination was deeply affected by spiking multiwall carbon nanotubes and a modifier in carbon paste. Electron transfer coefficient, α, catalytic electron rate constant, k, and the exchange current density, j 0, for oxidation of codeine at the HTP-MWCNT-CPE were calculated using cyclic voltammetry. The calibration curve was linear over the range 0.2-844.7 µM with two linear segments, and the detection limit of 0.063 µM of codeine was obtained using differential pulse voltammetry. The modified electrode was separated codeine and acetaminophen signals by differential pulse voltammetry. The modified electrode was applied for the determination of codeine and acetaminophen in biological and pharmaceutical samples with satisfactory results.

Electrosynthesis of an imidazole derivative and its application as a bifunctional electrocatalyst for simultaneous determination of ascorbic acid, adrenaline, acetaminophen, and tryptophan at a multi-wall carbon nanotubes modified electrode surface.

In this research, the electrosynthesis of 4-(1H-benzo[d]imidazol-2-ylthio)-5-methylbenze-1,2-diol (as an imidazole derivative) is reported. An imidazole derivative multi-wall carbon nanotube modified glassy carbon electrode (IMWCNT-GCE) was constructed and used as an excellent bifunctional electrocatalyst for oxidation of ascorbic acid (AA) and adrenaline (AD). Cyclic voltammetry was used to calculate the surface electron transfer rate constant, k(s), and the electron transfer coefficient, α, for the electron transfer between MWCNT-GCE and the electrodeposited imidazole derivative. The kinetic parameters such as the electron transfer coefficient, α, and the heterogeneous rate constant, k', for the oxidation of AA and AD at the IMWCNT-GCE surface were estimated. The modified electrode was found quite effective for the simultaneous determination of AA, AD, acetaminophen (AC), and tryptophan (Trp) in a mixture solution. The detection limits of AA and AD were calculated as 0.96 µM and 0.38 µM, respectively. Finally, IMWCNT-GCE was satisfactorily used for the determination of AA, AD, and AC in pharmaceutical samples.

Salicylic acid functionalized silica-coated magnetite nanoparticles for solid phase extraction and preconcentration of some heavy metal ions from various real samples.

A method for the preconcentration of trace heavy metal ions in environmental samples has been reported. The presented method is based on the sorption of Cu(II), Cd(II), Ni(II) and Cr(III) ions with salicylic acid as respective chelate on silica-coated magnetite nanoparticles. Prepared adsorbent was characterized by XRD, SEM, BET and FT-IR measurements. The metals content of the sorbed complexes are eluted using 4.0 mL of 1.0 mol L-1 nitric acid. The influences of the analytical parameters including pH, amount of solid phase and condition of eluting solution, the effects of matrix ions on the retention of the analytes were examined. The accuracy and precision of suggested method were tested by analyzing of certified reference materials. The detection limits (3Sb/m, N = 8) for Cu(II), Cd(II), Ni(II) and Cr(III) ions are 0.22, 0.11, 0.27 and 0.15 µg L-1, respectively, and the maximum preconcentration factor is 200. The method was successfully applied to the evaluation of these trace and toxic metals in various waters, foods and other samples.

Kinetic spectrophotometric method as a new strategy for the determination of vitamin B9 in pharmaceutical and biological samples.

In this study, a new method is proposed for the determination of trace amounts of folic acid (vitamin B(9)). This method is based on the inhibitory effect of folic acid on the reaction of Thionine and bromate in sulfuric acid media. The reaction can be monitored spectrophotometrically by measuring the decrease in absorbance at 601 nm (λ(max)). The effective variables on the reaction rate were investigated. Under optimum experimental conditions, the method allows to determine of the folic acid in a wide linear range with two linear segments. The limit of detection was 0.36 µg mL(-1) of folic acid. Relative standard deviations of six replicate determinations of 5.0 and 50.0 µg mL(-1) of folic acid were 1.18 and 1.02%, respectively. The interfering effect of the different species was also investigated. The method was evaluated by quantifying of folic acid in biological and pharmaceutical samples with satisfactory assay results.

Electrocatalytic oxidation and differential pulse voltammetric determination of using a carbon nanotubes modified electrode.

The electrocatalytic oxidation of hydroxylamine was studied at the surface of a carbon paste electrode (CPE) spiked with multi-wall carbon nanotubes (MWCNT) and 4-hydroxy-2-(triphenylphosphonio)phenolate (HTP). The modified electrode (HTP-MWCNT-CPE) exhibits an excellent electrochemical catalytic activity toward hydroxylamine oxidation. The results show that there is a dramatic enhancement on the anodic peak current of hydroxylamine oxidation at the HTP-MWCNT-CPE in comparison the value obtained at HTP-CPE and MWCNT-CPE. The kinetic parameters of the electron transfer coefficient, α, the heterogeneous electron transfer rate constant, k', and the exchange current density, j0, for oxidation of hydroxylamine at the HTP-MWCNT-CPE were determined using cyclic voltammetry. Differential pulse voltammetry exhibits three dynamic linear ranges of 2.0-10.0 µM, 10.0-1000.0 µM and 1000.0-8000.0 µM, and a lower detection limit of 0.16 µM for hydroxylamine. Finally, the modified electrode activity was studied for hydroxylamine determination in two water samples and satisfactory results were obtained.

Kinetic spectrophotometric method for the determination of morphine in biological samples.

In this paper a simple, selective and inexpensive kinetic method was developed for the determination of morphine based on its inhibitory effect on the Janus green-bromate system in sulfuric acid media. The reaction was monitored spectrophotometrically at 618 nm by a fixed time method. The effect of different parameters such as concentration of reactants and temperature on the rate of reaction was investigated and optimum conditions were obtained. The calibration curve was linear in the concentration range 0.07-7.98 mg L(-1) of morphine, and detection limit of the method was 3.0x10(-2)mg L(-1). The relative standard deviation for five determinations of 3.74 mg L(-1) of morphine was 0.57%. Finally, the proposed method was successfully applied to the determination of morphine in human urine and serum as real samples.

Kinetic spectrophotometric determination of trace amounts of iodide in food samples.

A simple, selective and sensitive kinetic method has been developed for the determination of trace amounts of iodide. This method is based on a catalytic effect of iodide on the reaction between Janus Green and bromate in acidic media. Trace amounts of iodide increase the rate of a reaction that is monitored spectrophotometrically at 618 nm by a fixed-time method at 30 s. Effective parameters on the reaction rate, such as the concentration of reactants, temperature and reaction time, were investigated and the optimum conditions were obtained (6.0 x 10(-2) mol L(-1) of sulfuric acid, 2.50 x 10(-5) mol L(-1) of Janus Green, 1.75 x 10(-2) mol L(-1) of bromate, 30 degrees C and 180 s). The calibration curve was linear between 0.5-190.0 microg L(-1) of iodide, and the relative standard deviations (n = 5) for 10.0 and 100.0 microg L(-1) of iodide were 1.2 and 1.8%, respectively. The limit of detection was 0.12 microg L(-1) of iodide concentration. The effects of various substances upon the reaction rate were determined for assigning the selectivity of the method. The proposed method was successfully applied to the determination of iodide in food samples. The new developed method was found to have fairly good selectivity, sensitivity, simplicity and rapidity.