For the first time, a capillary electrophoretic (CE) method with sample stacking induced by a reverse migrating pseudostationary phase (SRMP) technique has been developed and validated for sensitive determination of phenobarbital (PB) and its p-hydroxyphenobarbital (PHPB) metabolite in rat urine samples. Separation and determination were optimized on a fused-silica capillary with a total length of 50 cm (effective length 40 cm) and 75 μm ID. The microemulsion background electrolyte consisted of 0.8% (v/v) ethyl acetate, 6.6% (v/v) butan-2-ol, 1.0% (v/v) acetonitrile, 2.0% (w/v) sodium n-dodecyl sulfate (SDS), and 89.6% (v/v) of 7.5 mM ammonium formate at pH 8. When this preconcentration technique was used, the sample stacking and the separation processes took place successively with changing the voltage with an intermediate polarity switching step. For practical application, a solid-phase extraction (SPE), C(18) sorbent with n-hexane/ethyl acetate (1 : 1%, v/v) as the elution solvent was used for sample purification and concentration. The SPE method gave good extraction yields for all the analytes, with absolute recovery values of 96.9% and 99.1% for PB and PHPB, respectively. The regression equations for PB and PHPB showed excellent linearity over a concentration range of 55-1386 ng mL(-1) for PB and PHPB (r = 0.998). The developed microemulsion electrokinetic capillary chromatography (MEEKC) method for separation of the studied compounds with SRMP as the electrophoretic preconcentration technique allowed detection limits in urine samples at 16.8 ng mL(-1) for PB and PHPB which are 15-fold lower than the reported CE method in the literature. The precision results, expressed by the intra-day and inter-day relative standard deviation (RSD) values range from 3.6 to 7.1% (repeatability) and from 3.2 to 7.2% (intermediate precision) for PB and PHPB, respectively, which were in line with Food and Drug Administration (FDA) criteria.
a b s t r a c tThis paper investigates a search problem for a brownian target motion on one of n-intersected real lines in which any information of the target position is not available to the searchers all the time. We have n-searchers start searching for the target from the origin that is the intersection point of these lines. Each of the searchers moves continuously along his line in both directions of the starting point. The purpose of this paper is to formulate a search model and find the condition under which the expected value of the first meeting time between one of the searchers and the target is finite. Also, we show the existence of the optimal search plan which minimizes the expected value of the first meeting time and find it.
A simple, sensitive and accurate stability-indicating HPLC method has been developed and validated for determination of varenicline (VRC) in its bulk form and pharmaceutical tablets. Chromatographic separation was achieved on a Zorbax Eclipse XDB-C8 column (150 mm × 4.6 mm i.d., particle size 5 μm, maintained at ambient temperature) by a mobile phase consisted of acetonitrile and 50 mM potassium dihydrogen phosphate buffer (10:90, v/v) with apparent pH of 3.5 ± 0.1 and a flow rate of 1.0 ml/min. The detection wavelength was set at 235 nm. VRC was subjected to different accelerated stress conditions. The degradation products, when any, were well resolved from the pure drug with significantly different retention time values. The method was linear (r = 0.9998) at a concentration range of 2 - 14 μg/ml. The limit of detection and limit of quantitation were 0.38 and 1.11 μg/ml, respectively. The intra- and inter-assay precisions were satisfactory; the relative standard deviations did not exceed 2%. The accuracy of the method was proved; the mean recovery of VRC was 100.10 ± 1.08%. The proposed method has high throughput as the analysis involved short run-time (~ 6 min). The method met the ICH/FDA regulatory requirements. The proposed method was successfully applied for the determination of VRC in bulk and tablets with acceptable accuracy and precisions; the label claim percentages were 99.65 ± 0.32%. The results demonstrated that the method would have a great value when applied in quality control and stability studies for VRC.
Determination of donepezil hydrochloride in human plasma and pharmaceutical formulations by HPLC with fluorescence detectionA sensitive, isocratic reversed-phase high performance liquid chromatographic method involving fluorescence detection was developed for the determination of donepezil hydrochloride in tablets and in human plasma. Pindolol was used as an internal standard. Good chromatographic separation was achieved by using an analytical column C18. The system operated at room temperature using a mobile phase consisting of methanol, phosphate buffer (0.02 mol L-1) and triethyl amine (pH 3.5) (55: 45: 0.5,V/V/V) at a flow rate 0.9 mL-1min. The analyte and internal standard were extracted from human plasmavialiquid-liquid extraction. The proposed method was validated for sensitivity, selectivity, linearity, accuracy and precision. The calibration curve was linear over the range of 5-2000 ng mL-1of donepezil with detection limit of 1.5 ng mL-1. Intra- and inter-day relative standard deviations were less than 2.5 %. The method was found to be suitable for quality control of donepezil hydrochloride in bulk drug as well as in human plasma.
Recent advances in drug delivery systems have aimed to achieve better patient compliance. One of these advances is the formulation of orally disintegrating tablets (ODTs) that dissolve instantaneously, releasing drugs within a few seconds without the need of water. The main objective of this paper was to prepare and develop ODTs of clopidogrel. The ODTs were prepared by direct compression. The effect of three superdisintegrants, namely crospovidone, croscarmellose sodium, and sodium starch glycolate, using three different disintegration times on the dissolution rate was investigated. The prepared tablets were evaluated for hardness, friability, disintegration time and in vitro drug release. Furthermore, the interaction of clopidogrel with the formulation excipients was studied using differential scanning calorimetry (DSC). DSC studies revealed that there were no interactions between the drug and the excipients used. All tablets had hardness values in the range 4.0-5.2 kp and friability lower than 1%. The weight and drug content uniformity of all formulations was within official limits according to BP. In vitro drug release studies of the ODTs showed that more than 90% of the drug was released within ten minutes. A palatability test in human volunteers showed acceptable taste and mouth feel. Thus, the obtained results conclusively demonstrated successful rapid disintegration of the formulated tablets and acceptable palatability.Uniterms: Clopidogrel/orally disintegrating tablets. Superdisintegrants. Orally disintegrating tablets/ formulation. Orally disintegrating tablets/evaluation.Recentes avanços em sistemas de liberação de fármacos novos visam à obtenção de melhor adesão do paciente. Um destes avanços é a formulação de comprimidos de desintegração oral (ODTs), que se dissolvem instantaneamente, liberando o fármaco, em alguns segundos, sem a necessidade de água. O principal objetivo deste trabalho foi preparar e desenvolver ODTs de clopidogrel. Os ODTs foram preparados pelo método de compressão direta. Estudou-se o efeito de várias concentrações de diferentes agentes de desintegração, tais como super-crospovidona, croscarmelose de sódio, glicolato de amido de sódio no tempo de desintegração e velocidade de dissolução. Os comprimidos preparados foram avaliados quanto à dureza, à friabilidade, ao tempo de desintegração e à liberação do fármaco in vitro. Além disso, estudou-se a interação de clopidogrel com os excipientes de formulação, utilizando calorimetria de varredura diferencial (DSC). Estudos de DSC revelaram não haver interação entre o fármaco e os excipientes utilizados. Todos os comprimidos possuíam dureza na faixa de 4,0-5,2 kp e a friabilidade inferior a 1%. A variação de peso e o teor de fármaco de todas as formulações mostraram-se dentro do limite oficial, de acordo com a BP. O estudo de liberação do fármaco in vitro de comprimidos ODTs mostrou que mais de 90% do fármaco foram liberados em10 minutos. O teste de palatabilidade em voluntários humanos mostrou sabor e sensação na boca aceitáveis. Assim,...
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