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, j0, 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

Application of Fe3O4@SiO2/GO nanocomposite for sensitive and selective electrochemical sensing of tryptophan

A simple strategy for determination of tryptophan (TRP) based on Fe3O4@SiO2/GO nano­composite modified graphite screen printed electrode (Fe3O4@SiO2/GO/SPE) is re­ported. Cyclic voltammetry (CV) and differential pulse voltammetry (DPV) were used to characterize the performance of the sensor. The Fe3O4@SiO2/GO/SPE displayed excellent electro­che­mical catalytic activities. The oxidation overpotentials of tryptophan decreased significantly and its oxidation peak current increased dramatically at Fe3O4@SiO2/GO/SPE. Under the optimized experimental conditions tryptophan showed linear response over the range of 1.0-400.0 μM. The lower detection limit was found to be 0.2 μM for tryptophan. The prac­tical application of the modified electrode was demonstrated by measuring the concen­tration of tryptophan in real 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

A New Technique for Quantitative Determination of Dexamethasone in Pharmaceutical and Biological Samples Using Kinetic Spectrophotometric Method

Dexamethasone is a type of steroidal medications that is prescribed in many cases. In this study, a new reaction system using kinetic spectrophotometric method for quantitative determination of dexamethasone is proposed. The method is based on the catalytic effect of dexamethasone on the oxidation of Orange G by bromate in acidic media. The change in absorbance as a criterion of the oxidation reaction progress was followed spectrophotometrically. To obtain the maximum sensitivity, the effective reaction variables were optimized. Under optimized experimental conditions, calibration graph was linear over the range 0.2–54.0 mg L−1. The calculated detection limit (3sb/m) was 0.14 mg L−1 for six replicate determinations of blank signal. The interfering effect of various species was also investigated. The present method was successfully applied for the determination of dexamethasone in pharmaceutical and biological samples satisfactorily

A Novel Kinetic Spectrophotometric Method for the Determination of Dopamine in Biological and Pharmaceutical Samples

A sensitive and accurate method for quantitative determination of dopamine was introduced. The proposed method is based on inhibitory effect of dopamine on the oxidation of thionine by bromate in acidic media. The change in absorbance was followed spectrophotometrically at 601 nm. The dependence of sensitivity on the reaction variables was investigated and optimized to obtain the maximum sensitivity. Under optimum experimental conditions, calibration curve was linear over the range 0.2–103.3 μg mL−1 of dopamine. The relative standard deviations () of 0.5, 1.0, 5.0, and 30.0 μg mL−1 of dopamine were 1.13, 1.02, 0.99, and 0.97%, respectively. The limit of detection was 0.057 μg mL−1 of dopamine. The effect of diverse species was also investigated. The developed method was successfully applied for the determination of dopamine in pharmaceutical and biological samples

Spectrophotometric Determination of Hg2+ after Solid Phase Extraction on Microcrystalline Naphthalene

ABSTRACT Mercury is quantitatively retained with 1, 5-diphenylcarbazone (DPC) on microcrystalline naphthalene in the pH range 6.5-8.5 from a large volume of aqueous solutions of various samples. After filtration, the solid mass consisting of the mercury complex and naphthalene was dissolved in 5.0 mL of dimethylformamide (DMF) and mercury was determined by spectrophotometric method at 542 nm against the reagent blank. The linear calibration range for mercury was 30-1800 1.tg L-1 in DMF solution with a detection limit of 20 lug L-1. The relative standard deviation for eight replicate measurements of 1.0 [ig of mercury in 5.0 mL of DMF was 2.5%. The effect of potential interfering ions was investigated and the proposed method was applied to the determination of mercury in water samples

Application of Ion Mobility Spectrometry for Determination of Morphine in Human Urine

Abstract: In this study, a rapid, simple and sensitive ion mobility spectrometry (IMS) method with corona discharge as ionization source was described for the morphine determination in human urine. Morphine was extracted and purified from urine samples using solid phase extraction procedure with C 18 column. It can offer the clean extracts which no extra peaks were observed in IMS. Under operating experimental conditions (Temperature; injection: 220 and oven: 180 o C, Flow rate; carrier: 300 and drift: 600 mL min -1 , Voltage; corona: 2200 and drift: 6700 V), developed method showed good linearity in the ranges of 0.44 to 6.91 and 6.91 to 22 ng mL -1 with correlation coefficients (R 2 ) of 0.9979 and 0.9966, respectively. The limit of detection was 0.1 ng mL -1 , and precision as relative standard deviation was 11%. The capability of the proposed method was evaluated by the analysis of human urine as a real sample that satisfactory results were obtained

Thionine-Bromate as a New Reaction System for Kinetic Spectrophotometric Determination of Hydrazine in Cooling Tower Water Samples

A simple, selective, and inexpensive kinetic method was developed for the determination of hydrazine based on its inhibitory effect on the thionine-bromate system in sulfuric acid media. The reaction was monitored spectrophotometrically at 601 nm by a fixed time method. The effect of different parameters such as concentration of reactants, ionic strength, temperature, and time on the rate of reaction was investigated, and the optimum conditions were obtained. Under optimum conditions, the calibration curve was linear in the concentration range from 0.8–23.0 μg mL−1 of hydrazine, and the detection limit of the method was 0.22 μg mL−1. The relative standard deviation for five replicate determinations of 1.0 μg mL−1 of hydrazine was 0.74%. The potential of interfering effect of foreign species on the hydrazine determination was studied. The proposed method was successfully applied for the determination of hydrazine in different water samples

Adsorptive removal of thallium(III) ions from aqueous solutions using eucalyptus leaves powders

380-384Adsorption of thallium(III) ions from aqueous solutions onto eucalyptus leaves powders as a low cost adsorbent has been studied in batch mode. It is observed that modification of the adsorbent with basic solution (NaOH solution) is essential for achieving a significant adsorption. The alkaline modified adsorbent shows a significant amount of adsorption. However, the adsorbent treated with nitric acid shows no activity. The effects of experimental conditions such as initial solution pH, agitation speed, contact time, adsorbent amounts, initial thallium concentration and temperature are studied. The results show that adsorption is strongly pH-dependent. The maximum adsorption of thallium(III) ion obtained at 25±1oC is found to be 78.2%. The equilibrium data are described by the Langmuir isotherm but a slightly inferior fit is obtained using the Freundlich model. The monolayer saturation capacity is calculated to be 217.4 mg g-1. The separation factor indicates that eucalyptus leaves powders are favorable for the sorption of thallium(III). </span