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A kinetic spectrophotometric method that is sensitive and simple has been developed for the quantification of the venlafaxine hydrochloride in bulk as well as in pharmaceutical preparations. In this technique, venlafaxine is oxidized in the presence of alkaline potassium permanganate as an oxidizing agent and sodium hydroxide as a basic medium, and the reaction is carried out at room temperature. Due to the production of a manganate ion, the spectrophotometric measurement was performed at 610 nm. A fixed-time-based approach (15 min) was used to plot calibration graphs. The proposed method was optimized for all the conditions of reaction, whereby the linearity range was found to be 5–30 μg/mL with a limit of detection of 0.07 μg/mL. For the quantification of venlafaxine hydrochloride in a dosage form, the developed method was successfully applied and the percentage recovery was 98.87–100.22%. Statistical comparison was done for the obtained results with those of an official method and no significant differences regarding precision and accuracy were found. [ABSTRACT FROM AUTHOR]

A simple, rapid, sensitive and selective kinetic spectrophotometric method for determination of Fe(III) traces was elaborated in this paper. It is based on the catalytic effect of Fe(III) ions on oxidation of potassium salt of disulphonated hydroquinone (K2S2Hy) by hydrogen peroxide in acidic media, at a constant ionic strength. At the working temperature of 20°C and the wavelength of 450.0 nm, optimal conditions for determination of iron were found so that iron (III) can be determined by the proposed method in the concentration range of 1.87 to 18.7 ng cm-3. Corresponding RSD values were determined to be in the range 4.22 to 10.33 %. The limit of detection (LOD) calculated in two ways was found to be 1.07 ng cm-3 i.e. 1.11 ng cm-3 Fe(III). In order to assess the selectivity of the method effects of different ions on the reaction rate were also determined. It was found that presence of oxalates and citrates in the w/w ratio to Fe(III) 1:1 under selected experimental conditions interferes with determination of iron. Then the method was applied for determination of Fe(III) traces in white radish juice. The results agreed well with those obtained by atomic absorption spectrometry.

A new, simple, rapid, sensitive and selective kinetic spectrophotometric method for Pd(II) traces determination was elaborated in this paper. It is based on the catalytic effect of palladium ions upon the oxidation of methylene blue B (MBB) by (NH4)2S2O8 (APS) in citric buffer (BUF) solution. At the working temperature of 25 C and the wavelength of 662.4 nm, the optimal conditions for palladium determination were found. RSD value was found to be 2.6 to 4.9% for the investigated concentration range of Pd(II). Limit of detection (LD) was found to be 2.0 ng cm–3 Pd(II), and limit of quantification (LQ) is 6.9 ng cm–3 Pd(II). Only the presence of Pb2+, Hg2+ and Sn2+ in the reaction mixture interferes the determination of palladium by this method, while Au3+ and Ag+ have the catalytic effect upon the reaction rate. By this method, it is possible to determine the Pd(II) traces in the concentration range of 3.3x10–8 to 1.0x10–6 g cm–3. The method was confirmed by determination of Pd(II) traces in alloy PtRhG as well as in the powder of Pt. The obtained results were compared to those obtained by ICP-OES method and good agreement of results was found. [Project of the Serbian Ministry of Education, Science and Technological Development, Grant no. 172051]

A new, simple, rapid, sensitive and selective spectrophotometric kinetic method for Ag(I) traces determination at room temperature was elaborated in this paper. It is based on catalytic effect of silver ions upon the oxidation of methylene blue B (MBB) by K2S2O8 (PPS) in citric buffer (BUF) solution. The method was confirmed by determination of Ag(I) in PbO. The obtained results were compared to those obtained by ICP-OES method and good agreement of results was found. [Projekat Ministarstva nauke Republike Srbije, br. 172051]

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The present paper describes two new, simple, rapid, selective and sensitive kinetic spectrophotometric methods for Co(II) and Sn(II) determination in solution at room temperature, based on their effect on phenyl fluorone (PF) oxidation by hydrogen peroxide in ammonia buffer. The new method was elaborated for nano amounts of Co(II) determination, based on its catalytic effect on the oxidation of PF by H2O2 in the presence of citric acid (CA) as an activator. Also, the new method for micro amounts of Sn(II) determination was developed based on its inhibitory effect upon the same reaction. Comparison of the results showed that the activated catalytic reaction has better sensitivity than the inhibitory one. Methods were validated by the analyze of chemical substances and results were improved by examining the same samples by AAS method. [Projekat Ministarstva nauke Republike Srbije, br. 172051]

A new, sensitive and simple kinetic method has been developed for the determination of traces of Co(II) ions based on their catalytic effect in the oxidation of trisodium-2-hydroxy-1-(4-sulphonato-1-naphthylazo)naphthalene-6,8-disulphonate (red artificial color Ponceau 4R) by hydrogen peroxide in borate buffer. The reaction was followed spectrophotometrically by tracing the oxidation product at 478.4 nm within 1 min after the imitation of the reaction. The optimum reaction conditions are: borate buffer (pH = 10.50), Ponceau 4R (8 × 10–6 mol/dm3), H2O2 (3 × 10–2 mol/dm3) at 22 ºC. Following this procedure, Co(II) can be determined with a linear calibration graph up to 1.17 ng/cm3 and a detection limit of 0.20, based on the 3s criterion. The relative error ranges between 4.80–3.25 % for the concentration interval of Co(II) ions 1.76–17.61 ng/cm3. The effects of certain foreign ions the reaction rate were determined for an assessment of the selectivity of the method. The method was applied for the determination of Co(II) in pharmaceutical samples.

Anew, sensitive and simple kinetic method has been developed for the determination of traces of Co(II) ions based on their catalytic effect in the oxidation of trisodium-2-hydroxy-1-(4-sulphonato-1-naphthylazo)naphthalene-6,8-disulphonate (red artificial color Ponceau 4R) by hydrogen peroxide in borate buffer. The reaction was followed spectrophotometrically by tracing the oxidation product at 478.4 nm within 1 min after the initiation of the reaction. The optimum reaction conditions are: borate buffer (pH 10.50), Ponceau 4R (8 x10-6 mol/dm3), H2O2 (3 x10-2 mol/dm3) at 22 ºC. Following this procedure, Co(II) can be determined with a linear calibration graph up to 1.17 ng/cm3 and a detection limit of 0.20, based on the 3criterion. The relative error ranges between 4.80-3.25 % for the concentration interval of Co(II) ions 1.76-17.61 ng/cm3. The effects of certain foreign ions on the reaction rate were determined for an assessment of the selectivity of the method. The method was applied for the determination of Co(II) in pharmaceutical samples.

Copyright of Chemical Industry / Hemijska Industrija is the property of Association of Chemical Engineers and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

A simple, cost effective, highly sensitive and rapid kinetic spectrophotometric method was developed for hydrazines by using Thiophene-3-carboxaldehyde (3-Thienaldehyde) and 3-Butenone (E)-1,1,1-trifluoro-4-(3-thienyl) (CF3 enone). CF3 enone was prepared by crossed aldol condensation of 3-Thienaldehyde and characterized by UV-Vis, FT-IR and NMR spectra. Reactions of 3-Thienaldehyde (with catalyst) and CF3 enone (in acetonitrile medium without catalyst) with hydrazines were followed spectrophotometrically and compared. Variables such as temperature and concentration were optimized to determine hydrazines in the concentration range of 0.1 mM to 0.1 M for 3-Thienaldehyde and 0.1 mM to 1 mM for CF3 enone. Minimum detectable limits were found to be 0.2 mM (Hydrazine) and 0.1 mM (MMH ) for 3-Thienaldehyde. For CF3 enone, Minimum detectable limits were found to be 0.007 mM (Hydrazine) and 0.01 mM (MMH). Rate of the CF3 enone reaction was studied as there is gradual decrease in absorbance for the peak at 320 nm for the interaction of hydrazines. Initial rate and fixed time methods were adopted for kinetic study. CF3 enone based kinetic spectrophotometric method is rapid and sensitive with no catalyst requirement for interaction of hydrazines when compared with the classical CHO functional group based method [ABSTRACT FROM AUTHOR]

The aim of this work was to establish the deformation behavior of two vanadium microalloyed medium carbon steels with different contents of carbon and titanium by tensile testing at 77 K. Samples were reheated at 1250 °C for 30 min and continuously cooled in still air. Beside acicular ferrite as the dominant morphology in both microstructures, the steel with lower content of carbon and negligible amount of titanium contains considerable fraction of grain boundary ferrite and pearlite. It was found that Ti-free steel exhibits a higher strain hardening rate and significantly lower elongation at 77 K than the fully acicular ferrite steel. The difference in tensile behavior at 77 K of the two steels has been associated with the influence of the pearlite, together with higher dislocation density of acicular ferrite. [ABSTRACT FROM AUTHOR]

A new analytical method using Back-Propagation (BP) artificial neural network and kinetic spectrophotometry for simultaneous determination of iron and magnesium in tap water, the Yellow River water and seawater is established. By conditional experiments, the optimum analytical conditions and parameters are obtained. Levenberg-Marquart (L-M) algorithm is used for calculation in BP neural network. The topological structure of three-layer BP ANN network architecture is chosen as 15-16-2 (nodes). The initial value of gradient coefficient µ is fixed at 0.001 and the increase factor and reduction factor of µ take the default values of the system. The data are processed by computers with our own programs written in MATLAB 7.0. The relative standard deviation of the calculated results for iron and manganese is 2.30% and 2.67% respectively. The results of standard addition method show that for the tap water, the recoveries of iron and manganese are in the ranges of 98.0%-104.3% and 96.5%-104.5%, and the RSD is in the range of 0.23%-0.98%; for the Yellow River water (Lijin district of Shandong Province), the recoveries of iron and manganese are in the ranges of 96.0%-101.0% and 98.7%-104.2%, and the RSD is in the range of 0.13%-2.52%; for the seawater in Qingdao offshore, the recoveries of iron and manganese are in the ranges of 95.3%-104.8% and 95.3%-104.7%, and the RSD is in the range of 0.14%-2.66%. It is found that 21 common cations and anions do not interfere with the determination of iron and manganese under the optimum experimental conditions. This method exhibits good reproducibility and high accuracy in the determination of iron and manganese and can be used for the simultaneous determination of iron and manganese in tap water and natural water. By using the established ANN-catalytic spectrophotometric method, the iron and manganese concentrations of the surface seawater at 11 sites in Qingdao offshore are determined and the level distribution maps of iron and manganese are drawn. [ABSTRACT FROM AUTHOR]

A new selective, sensitive, and simple kinetic method is developed for the determination of trace amounts of chromium (VI). The method is based on the catalytic effect of Cr(VI) on the reaction of sodium pyrogallol-5-sulphonate ( PS) with hydrogen peroxide. The reaction is followed spectrophotometrically by tracing the oxidation product at 437 nm within 1 min after addition of H2O2. The optimum reaction conditions are PS (1.32·10−3 mol·dm−3), H2O2 (0.32 mol·dm−3), HClO4 (2.6·10−3 mol·dm−3) at 25°C. Following this procedure, chromium (VI) can be determined with a linear calibration graph up to 0.25 ng·cm−3 and a detection limit of 0.024 ng·cm−3, based on the 3σ criterion. The interference effect of several species was also investigated and it was found that the most common cations and anions do not interfere with the determination. The developed procedure was successfully applied to the determination of Cr(VI) and total Cr in river waters and total Cr in herbal samples. [ABSTRACT FROM AUTHOR]