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Gold modified nanoporous silica based magnetic microparticles have been prepared as support for the immobilization of the enzyme horseradish peroxidase (HRP). The enzyme modified gold microparticles were retained onto the surface of a solid carbon paste electrode with the help of a permanent magnet. The analytical performances of the resulting biosensor were characterized by studying hydroquinone (HQ) and hydrogen peroxide. The former was monitored by the direct electroreduction of the biocatalytically generated quinone. Several experimental parameters influencing the biosensor response were investigated. A linear response to HQ was obtained in the concentration range comprised between 5 Â 10 À7 and 4.5 Â 10 À6 M with a detection limit of 4 Â 10 À7 M. The enzyme electrode provided a linear response to hydrogen peroxide over a concentration range comprised between 5 Â 10 À7 À 1.3 Â 10 À4 M with a detection limit of 4 Â 10 À7 M. The inhibition of the biosensor response in the presence of thiols e.g. cysteine, captopril, glutathione and Nacystelyn (NAL) has been pointed out.

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A new oxymetazoline (OM) ion-selective PVC membrane electrode based on the ion associate of OM with phosphotungstic acid was prepared. The electrode exhibits a linear response with a mean calibration graph slope of 57.16 mV decade -1 at 25˚C within the concentration range of 1.96 × 10 -5 -1 × 10 -2 M OMCl. The change in the pH within the range of 1.0 -9.4 did not affect the electrode performance. The standard electrode potentials were determined at different temperatures and used to calculate the isothermal coefficient of the electrode (-0.001233 V). The electrode showed a very good selectivity for OM with respect to a large number of inorganic cations and compounds. The standard addition method and potentiometric titration were applied to the determination of (OM) with RSD not exceeding 1.19%.

Mebeverine hydrochloride (MB), 4-[ethyl(4-methoxy-α-methylphenethyl)amino]butyl veratrate hydrochloride [2753-45-9], is a potent direct antispasmodic acting mainly on the smooth muscles of the gastrointestinal tract; it is particularly effective against colonic spasms. 1 Sulpiride (SU), N-(1-ethylpyrrolidin-2-ylmethyl)-2-methoxy-5-sulfamoyl benzamide [15676-16-1], is a substituted benzamide antipsychotic which is reported to be a selective antagonist of central dopamine (D2, D3 and D4) receptors. It is also claimed to have mood-elevating properties. 1The binary mixture of the two drugs is used in the treatment of gastointestinal and colic spasms, specially in the presence of psychasomatic manifestations of nervous tension, mental stress or anxiety. Several analytical methods have been used for the determination of MB, including high performance liquid chromatography (HPLC), 2-4 thin layer chromatography (TLC), 5,6 spectrophotometric methods 25 first used derivative UV spectrophotometry, TLC-densitometry and HPLC for the simultaneous determination of both of these two compounds in pharmaceutical tablets. In this study, ratio spectra first derivative spectrophotometry and classical least squares method are proposed for simultaneous determination of MB and SU in their mixtures and their pharmaceutical preparation, Colona tablets. The proposed ratio spectra first derivative method was found to be more sensitive than the published UV first derivative method 25 (Beer's law linear range was 4.0 -40.0 and 1.0 -10.0 µg/ml for MB and SU, respectively while the linear range was 10.0 -30.0 and 2.0 -8.0 µg/ml in the first derivative published method). The proposed chemometric method was more rapid, simple than the published methods. 25 Also, the proposed methods can be used as alternative methods to those reported for the simultaneous determination of MB and SU. Experimental ApparatusA Shimadzu 1601 double beam UV-Vis spectrophotometer with a fixed slit width (2 nm) connected to an IBM compatible computer and a HP 600 inkjet printer was used. The bundled software was UV PC personal spectroscopy version 3.91 (Shimadzu). MaterialsMB, SU and Colona tablets containing 100 mg MB and 25 mg SU per tablet, were kindly supplied by Rameda (6 October City, Egypt). Analytical grade methanol and hydrochloric acid were used throughout these experiments. Standard solutionsStock solutions of MB and of SU were prepared separately by dissolving 100 mg and 10 mg of each drug, respectively, in 100 ml methanol. The standard solutions were prepared by dilution of the stock solutions with 0.1 M HCl to reach a concentration range of 4 -20 and 1 -10 µg/ml for MB and SU, respectively. Faculty of Industrial Education, Beni Suef, EgyptTwo methods are described for the simultaneous determination of mebeverine hydrochloride (MB) and sulpiride (SU) in their combinations. The first method depends on the first derivative of the ratio spectra by measurement of the amplitudes at 263.7 and 234.9 nm for MB and SU, respectively. The linear ranges and detection...

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