Electroanalysis with tungsten electrodes : I. The tungsten/platinum bimetallic pair in potentiometry at zero current

The W/Pt bimetallic pair has been applied in various potentiometric titrations. Except for the neutralization of dicarboxylic acids, e.g., oxalic, the pair is suitable for neutralization titrations where ΔE/ΔV values at the equivalence point are higher on W than on Pt. Tungsten oxides increase the inflexion pd. The pair is also suitable for oxidation/reduction titrations using permanganate, dichromate, and ceric sulfate, and for precipitation reactions with silver nitrate. However, it gives a small inflexion pd in the oxidation of thiosulfate by iodine. EDTA titrations of copper, magnesium, and calcium give a sharp inflexion in the case of copper only. This pair may be useful in routine analyses requiring a robust electrode assembly but not a high degree of accuracy.     

The Application of Fractal Transform and Entropy for Improving Fault Tolerance and Load Balancing in Grid Computing Environments

This paper applies the entropy-based fractal indexing scheme that enables the grid environment for fast indexing and querying. It addresses the issue of fault tolerance and load balancing-based fractal management to make computational grids more effective and reliable. A fractal dimension of a cloud of points gives an estimate of the intrinsic dimensionality of the data in that space. The main drawback of this technique is the long computing time. The main contribution of the suggested work is to investigate the effect of fractal transform by adding R-tree index structure-based entropy to existing grid computing models to obtain a balanced infrastructure with minimal fault. In this regard, the presented work is going to extend the commonly scheduling algorithms that are built based on the physical grid structure to a reduced logical network. The objective of this logical network is to reduce the searching in the grid paths according to arrival time rate and path’s bandwidth with respect to load balance and fault tolerance, respectively. Furthermore, an optimization searching technique is utilized to enhance the grid performance by investigating the optimum number of nodes extracted from the logical grid. The experimental results indicated that the proposed model has better execution time, throughput, makespan, latency, load balancing, and success rate.     

Odd-Excited Binomial States of the Radiation Field and Some of Their Statistical Properties

In this paper a new state called odd-excited binomial state (OEBS) is introduced. It interpolates between the odd number state and the odd-excited coherent state. We discuss some statistical properties, such as the Glauber second-order correlation function and squeezing phenomenon (normal and amplitude-squared squeezing) for this state. The quasiprobability distribution functions (Husimi Q-function and Wigner W-function) are also examined.     

Quantum Properties of Odd Excited Negative Binomial States of the Radiation Field

The odd excited negative binomial states are introduced using the photon creation operator by repeated application on negative binomialstates. These states interpolate between the odd displaced Fock states and the odd excited pure thermal states. In this paper both squeezing phenomena (normal squeezing and amplitude squared squeezing) are discussed. Besides discussion of the Glauber second-order correlation function, investigations are carried out for the quasi-probability distribution functions (Wigner function and Q-function). Finally the Pegg-Barnett phase probability distribution is computed for these states.     

Spectrofluorimetric Determination of Fluvoxamine in Dosage Forms and Plasma Via Derivatization with 4-Chloro-7-Nitrobenzo-2-Oxa-1,3-Diazole

A highly sensitive and simple spectrofluorimetric method has been developed and validated for the determination of the antidepressant fluvoxamine (FXM) in its dosage forms and plasma. The method was based on nucleophilic substitution reaction of FXM with 4-chloro-7-nitrobenzo-2-oxa-1,3-diazole in an alkaline medium (pH 8) to form a highly fluorescent derivative that was measured at 535 nm after excitation at 470 nm. The factors affecting the reaction was carefully studied and optimized. The kinetics of the reaction was investigated, and the reaction mechanism was presented. Under the optimized conditions, linear relationship with good correlation coefficient (0.9995) was found between the fluorescence intensity and FXM concentration in the range of 65–800 ng ml⁻¹. The limits of detection and quantitation for the method were 21 and 64 ng ml⁻¹, respectively. The precision of the method was satisfactory; the values of relative standard deviations did not exceed 2.17%. The proposed method was successfully applied to the determination of FXM in its pharmaceutical tablets with good accuracy; the recovery values were 97.8–101.4 ± 1.08–2.75%. The results obtained by the proposed method were comparable with those obtained by the official method. The high sensitivity of the method allowed its successful application to the analysis of FXM in spiked human plasma. The proposed method is superior to the previously reported spectrofluorimetric method for determination of FXM in terms of its simplicity. The proposed method is practical and valuable for its routine application in quality control and clinical laboratories for analysis of FXM.     

The racemization of an optically active sulfilimine and optically active aminosulfonium salts

The racemization of an optically active sulfilimine and optically active aminosulfonium salts was kinetically measured. The mechanism of the racemization of optically active sulfilimine (?)-1 has been established. The activation parameters for the racemization of (?)-1 and (?)-7 were calculated. A plausible pathway for the decomposition of (?)-6, (?)-7 and (?)-8 with tetra-n-butylammonium bromide in the presence of methyl ethyl ketone to provide 3-p-tolylthio-2-butanone 22 is proposed.     

A highly sensitive and specific polyclonal antibody-based enzyme immunoassay for therapeutic monitoring and pharmacokinetic studies of atorvastatin

This study describes the development and validation of a highly sensitive and specific enzyme immunoassay (EIA) for therapeutic monitoring and pharmacokinetic studies of atorvastatin (ATR). The assay employs a polyclonal antibody that recognizes ATR with high specificity and affinity, and ATR conjugated to bovine serum albumin (ATR-BSA) immobilized onto microwell plates as a solid phase. The assay involved a competitive binding reaction between ATR and the immobilized ATR-BSA for the binding sites on a limiting amount of the anti-ATR antibody. The bound anti-ATR antibody was quantified with horseradish peroxidase-labeled anti-immunoglobulin secondary antibody and 3,3′,5,5′-tetramethylbenzidine as a substrate for the peroxidase enzyme. The concentration of ATR in the sample was quantified by its ability to inhibit the binding of the anti-ATR antibody to the immobilized ATR-BSA and subsequent color development in the assay wells. The conditions for the EIA were investigated and optimized for the determination of ATR in plasma samples. The limit of detection was 0.04 ng mL^?1 and the effective working range at relative standard deviations (RSD) of ≤5% was 0.1–10 ng mL^?1. Mean analytical recovery of ATR from spiked plasma was 99.3?±?2.8%. The precision of the assay was satisfactory; RSD were 2.7–4.6 and 3.3–5.7% for intra- and inter-assay precision, respectively. The reliability of the EIA was confirmed by HPLC. The EIA is convenient, and one can analyze ～ 200 samples per working day, facilitating the processing of large-number of samples of ATR.     

Study of Interactions Between Sugammadex and Penicillins Using Affinity Capillary Electrophoresis

Sugammadex, a new modified gamma cyclodextrin, reverses the neuromuscular blockage induced by rocuronium by forming a strong complex with this muscle relaxant. To evaluate possible interactions with potentially co-administered drugs, interactions between sugammadex and penicillins were investigated using the affinity capillary electrophoresis method for the first time. Capillary electrophoresis coupled to an ultra violet detector was used as an analytical device for the analysis and detection of cyclodextrin inclusion complexes. Changes in the effective mobility of guest drugs (amoxicillin, ampicillin, oxacillin, dicloxacillin and azlocillin) were correlated with the increasing concentration of host molecules in background electrolyte, and successfully fitted into a non-linear curve equation; assuming 1:1 stoichiometric interaction. The calculated association constants (K _a) were: 383.44, 184.54, 265.34 and 95.06 M⁻¹ for amoxicillin, ampicillin, oxacillin and dicloxacillin, respectively. No complex formation with sugammadex could be detected for both penicillin G and piperacillin. The difference in the chemical structure of the penicillins, especially in the (R) side chains, is suggested to be responsible for the variety of binding strength between penicillins and sugammadex. The displacement study demonstrated that interactions between sugammadex and co-administered penicillins could reduce the pharmacological effects of both.

     

New methods for determination of cinnarizine in mixture with piracetam by spectrodensitometry, spectrophotometry, and liquid chromatography

Four new methods were developed and validated for the determination of cinnarizine HCl in its binary mixture with piracetam in pure and pharmaceutical preparations. The first one was a densitometric analysis that provides a simple and rapid method for the separation and quantification of cinnarizine HCI. The method depends on the quantitative densitometric evaluation of thin-layer chromatograms of cinnarizine HCI at 252 nm over concentration range of 1-6 microg/spot, with a mean accuracy of 100.05 +/- 0.91%. The second method was determination of the drug using a colorimetric method that utilizes the reaction of 3-methyl-benzothiazolin-2-one in the presence of FeCl3 as an oxidant. The green color of the resulting product was measured at 630 nm over concentration range 10-40 microg/mL, with a mean accuracy of 100.10 +/- 1.13%. The third method was a direct spectrophotometric determination of cinnarizine HCI at 252 nm over the concentration range 7-20 microg/mL, while piracetam was determined by derivative ratio spectrophotometry at 221.6 nm over concentration range 5-30 microg/mL, with a mean accuracy of 100.14 +/- 0.79 and 100.26 +/- 1.24% for cinnarizine HCI and piracetam, respectively. The last method was a liquid chromatography analysis of both cinnarizine HCI and piracetam, depending on quantitative evaluation of chromatograms of cinnarizine HCI and piracetam at 252 and 212 nm, respectively, over the concentration range 10-200 microg/mL for cinnarizine HCI and 20-500 microg/mL for piracetam, with a mean accuracy of 100.03 +/- 0.89 and 100.40 +/- 0.94% for cinnarizine HCI and piracetam, respectively. The proposed procedures were checked using laboratory-prepared mixtures and successfully applied for the analysis of their pharmaceutical preparations. The validity of the proposed procedures was further assessed by applying the standard addition technique. Recoveries were quantitative, and the results obtained agreed with those obtained by other reported methods.