Search Results
Summary
Dispersive liquid-liquid microextraction in combination with an in situ derivatization is suggested for parabens sampling and preconcentration. The derivatization was carried out with acetic anhydride under alkaline conditions maintained using di-potassium hydrogen phosphate. The effects of an extraction solvent type, extraction and disperser solvents volume, extraction time, and ionic strength of the solution on the extraction efficiency were investigated. Chlorobenzene containing n-hexadecane as internal standard was used as an extracting solvent and acetone was used as a disperser solvent. The calibration graphs were linear up to 10 mg mL−1, correlation coefficients were 0.997–0.999, enrichment factors were from 70 for methylparaben to 210 for butylparaben, and detection limits were 22, 4.2, 3.3, and 2.5 µg L−1 for methylparaben, ethylparaben, propylparaben, and butylparaben, respectively. Repeatabilities of the results were acceptable with relative standard deviations up to 11%. A possibility to apply the proposed method for parabens determination in water samples was demonstrated.
Summary
An isocratic reversed-phase high-performance liquid chromatographic (RPHPLC) method for analysis of irinotecan HCl has been developed and validated. Separation was achieved on a C18 column with potassium dihydrogen phosphate buffer (pH adjusted to 3.5 with orthophosphoric acid)-acetonitrile-methanol 55:25:20 (v/v) as mobile phase at a flow rate of 1.0 mL min−1. UV detection was performed at 254 nm. The method is simple, sensitive, rapid, and selective, and linear over the range 30–70 μg mL−1 for assay of irinotecan HCl. The precision of the assay method was below 1.0% RSD. Mean recovery was in the range 98.0–102.0%. Recovery of the active pharmaceutical ingredient from dosage forms ranged from 99.0 to 101.0. The method is useful for quality control in bulk manufacture and of the pharmaceutical formulation.
Summary
This paper reports development and validation of a new microemulsion liquid chromatographic (MELC) method for rapid screening of simvastatin and simvastatin acid in human plasma. Plasma samples were injected directly into the HPLC system after appropriate sample dilution with mobile phase. Separations were performed on a 4.6 mm × 150 mm, 5-μm particle, C18 column, with UV detection at 238 nm. The mobile phase was 0.5% (w/υ) diisopropyl ether, 1.0% (w/υ) sodium dodecylsulphate (SDS), 4.0% (w/v) n-butanol, and 94.5% (w/w) aqueous 25 mM disodium hydrogen phosphate, pH 7.0, at a flow rate of 1 mL min−1. The method was evaluated according to criteria stated in FDA bioanalytical method validation guidance. The unique approach applied in this paper enables direct analysis of simvastatin and simvastatin acid, so the method can be used to obtain reliable results in a rapid and simple way.
The practical challenge of creating a Hungarian e-mail reader has initiated our work on statistical text analysis. The starting point was statistical analysis for automatic discrimination of the language of texts. Later it was extended to automatic re-generation of diacritic signs and more detailed language structure analysis. A parallel study of three different languages-Hungarian, German and English-using text corpora of a similar size gives a possibility for the exploration of both similarities and differences. Corpora of publicly available Internet sources were used. The corpus size was the same (approximately 20 Mbytes, 2.5-3.5 million word forms) for all languages. Besides traditional corpus coverage, word length and occurrence statistics, some new features about prosodic boundaries (sentence initial and final positions, preceding and following a comma) were also computed. Among others, it was found that the coverage of corpora by the most frequent words follows a parallel logarithmic rule for all languages in the 40-85% coverage range, known as Zipf's law in linguistics. The functions are much nearer for English and German than for Hungarian. Further conclusions are also drawn. The language detection and diacritic regeneration applications are discussed in detail with implications on Hungarian speech generation. Diverse further application domains, such as predictive text input, word hyphenation, language modelling in speech recognition, corpus-based speech synthesis, etc. are also foreseen.
A „Steindl-füzetek”. Egy forrás a dualizmus kori építészképzés történetének historiográfiai megközelítéséhez
Imre Steindl’s Notes. A new source for the historiographical study of the architectural education in Austria-Hungary
Imre Steindl (1839–1902) is thought to be one of the most prominent architects of the Hungarian Historicism, whose active contribution to the Hungarian Neo-gothic architecture and restoration practices can hardly be overestimated. Albeit, his activity as an architect of the renowned late chief work of the international Gothic Revival, the Hungarian Parliament, as a leader of a prosperous atelier and as a driving force in the public life of the Hungarian architects has been studied intensively, to his work as professor at the Joseph Technical University of Budapest has been so far less attention given. Steindl began to teach as an ordinary professor of medieval architecture in 1870 and shaped the curriculum and educational methods following the traditions of his former alma mater, the Academy Fine Arts of Vienna. In this study, beyond the outline of the long 19th-century Hungarian architectural education and analysis the educational principals typical of Steindl’s methods, the manuscript of the professor’s lecture notes is published and analyzed, with special regard to his historiographical orientation and scholarly reference points. The philological reading of the text points out, that Steindl compiled his lectures in question from the ‘great syntheses’ of the Berlin School of Art History, above all that of Wilhelm Lübke and Karl Schnaase. The detection of this kind of historiographical influence may contribute to the scholarship’s image of Steindl’s, furthermore the late 19th-century Hungarian architectural intelligentsia’s erudition.
Summary
A simple, rapid, precise, and accurate, stability-indicating reversed phase high performance liquid chromatographic method was developed and validated for simultaneous determination of metformin HCl and repaglinide. The chromatographic separation was achieved on YMC Pack AM ODS (5 μm, 250 mm length × 4.6 mm i.d.) column at a detector wavelength of 210 nm, using an isocratic mobile phase consisting of methanol and 10 mM potassium dihydrogen phosphate buffer (pH 2.5) in a ratio of 70:30 v/v at a flow rate of 1 mL min−1. The retention times for metformin and repaglinide were found to be 2.6 and 11.3 min, respectively. The drugs were exposed to thermal, photolytic, hydrolytic, and oxidative stress conditions, and the stressed samples were analyzed by the proposed method. Validation of the method was carried out as per International Conference on Harmonization (ICH) guidelines. Linearity was established for metformin and repaglinide in the range of 5–200 μg mL−1 and 1–200 μg mL−1, respectively. The limits of detection were 0.3 μg mL−1 and 0.13 μg mL−1 for metformin and repaglinide, respectively. The method was found to be specific and stability-indicating as no interfering peaks of degradants and excipients were observed. The proposed method is hence suitable for application in quality-control laboratories for quantitative analysis of both the drugs individually and in combination, since it is simple and rapid with good accuracy and precision.
Summary
Piperine is the bioactive constituent of black pepper (Piper nigrum). For quality control of piperine content, expensive instruments are usually used. A simple and inexpensive TLC image-analysis method for quantification of the piperine content of the traditional medicinal preparations of Bhutan has been established in this study. An image of the TLC chromatogram, under UV light at 254 nm, was taken by use of a digital camera and was further transformed to a density profile plot, along the direction of development, by use of Scion Image software. The concentration of piperine was calculated by comparing its peak area with a calibration plot established by chromatography of piperine standards on the same TLC plate. Linear regression analysis of the calibration data revealed a good linear relationship (R 2 = 0.9962) between response and amount of piperine in the range 0.34–1.03 μg per spot. The specificity, precision, accuracy, and recovery of the method are satisfactory. The analytical results obtained by use of the method were not significantly different from those obtained by use of densitometric TLC. A disadvantage of the method is its low sensitivity — the limits of detection (LOD) and quantification (LOQ) were 15.36 and 46.54 ng per spot, respectively.
Summary
A simple, rapid, and specific thin layer chromatographic (TLC) method has been developed and validated for the simultaneous estimation of icariin and l-arginine from commercial polyherbal formulations for sexual dysfunction. The separation of the methanol extract of these formulations was achieved on silica gel 60 F254 aluminum backed TLC plates by using ethyl acetate-acetone-glacial acetic acid-formic acid-water 12:2:1:2:2 (υ/υ) as mobile phase. Densitometric analysis of icariin and l-arginine was monitored in absorbance mode at 270 and 195 nm, respectively. The linear regression analysis data for the calibration plots for icariin and l-arginine showed good linear relationship with r 2 = 0.9984 +- 0.01 and 0.9968 +- 0.02, in the concentration ranges of 250–750 and 500–1500 ng/spot, respectively. The method was validated for precision, robustness, and recovery. The average percentage recovery was found to be 98.26% for icariin and 99.63% for l-arginine. The limits of detection and quantitation were 72, 116 and 238, 383 ng/spot, respectively, for icariin and l-arginine. Statistical analysis proves that the method is repeatable and selective for the estimation of the targeted drugs. Since the proposed mobile phase effectively resolves the icariin and l-arginine, this method can be applied for the identification and quantitation of these components in herbal extracts and marketed formulations.
The so called “Liber sequentiarum et sacramentarium” (Šibenik, Monastery of Franciscans the Conventuals), 11th Century
The Oldest Medieval Missal of Pula, Istria
Research of the manuscript hitherto known and labeled as the "Liber sequentiarum and sacramentarium" (“LS”), stored today in Šibenik, has shown that this chant book is the earliest missal copied in the monastery of Tegernsee for the St Thomas Basilica in medieval Pula, Istria.Indications for its provenance are drawn from its codicological, palaeographical and repertorial features. Beside the detailed comparison of its script, notation, sequence and trope repertory, this article shows up to date not analyzed repertory of the saints venerated in its sacramentary and in the list of relicts to be mentioned at the end of missal (Haec sunt reliquiae). Particularly, this portions of the “LS” repertory were a clue toward detection that the “Leitheiliger” of this chant book is St Thomas Apostle, a patron of the bishopric of Parenzo/Pula, to whom also the “unicum” sequence Armonia concinnans was dedicated. St Thomas Basilica in medieval Pula is place of usage where this “commissioned book” has been meant for liturgical usage. In the broader Aquileian context this manuscript is important as a “new source” from Aquileia and its eastern province of Istria.
Summary
Ezetimibe is the first in a new class of antihypercholesterolemic drugs. Since it has not long been available on the market, many of its properties may still be revealed. Analytical methods for its determination are scarce, especially regarding serum samples. A simple, fast, and effective high-performance liquid chromatography-ultraviolet (HPLC-UV) method for the determination of ezetimibe concentration in human serum has therefore been developed. Three mobile phases were analysed, and original modifications to the concentration and flow parameters were made. Of five potential internal standards (IS), only nitrendipine was found to be suitable. The analytical wavelength was chosen based on the absorption spectrum of ezetimibe in the mobile phase. Finally, an extraction analysis was performed using two different solvents, and the extrahent volume was optimised. The final method developed was as follows. Single extraction of 1 mL serum sample, spiked with IS, was performed using 10 mL of methyl-t-butyl ether. Separation was obtained at ambient temperature on a Waters C18 Symmetry Shield (4.6 mm × 250 mm, 5 μm) column. The isocratic mobile phase was composed of acetonitrile and 0.1 M ammonium acetate aqueous solution 55:45 (v/v), set at flow rate of 0.75 mL min−1. Ezetimibe was detected at a wavelength of 232 nm after 5.49 min, and the IS was detected at 8.05 min. The developed method has been validated according to ICH standards. It was found to be specific, precise, accurate and linear over the range 10–800 ng mL−1 with R 2 > 0.998, and detection and quantification limits of 4.60 ng mL−1 and 13.94 ng mL−1, respectively. The method has been applied to clinical serum samples. The developed technique allowed for successful in vivo assessment of ezetimibe concentrations in samples obtained from hypercholesterolemia patients who are chronically receiving the drug.
