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Summary

The urobilinogenic chlorophyll catabolites are secondary metabolites formed by the biodegradation of chlorophylls. The thermodynamic study of the urobilinogenic chlorophyll catabolites from autumnal leaves extract of Parrotia persica and Hamamelis virginiana was done using reversed-phase liquid chromatography on the C4 and C8 analytical columns with acidified water-methanol mobile phase in combination with ultraviolet detection and electrospray ionization mass spectrometry. The presence of the urobilinogenic chlorophyll catabolites was detected by their characteristic ultraviolet absorption and their molecular mass. The retention behaviors of the two urobilinogenic chlorophyll catabolite isomers over a temperature range of 278–318 K were investigated. The retention time data permitted the construction of the van't Hoff plots. The stationary phase composition influences the thermodynamics of the retention of the urobilinogenic chlorophyll catabolites. The study presented can find the application in the separation of the urobilinogenic chlorophyll catabolites in autumnal leaves extracts.

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In the present study, we have developed and validated an analytical method for the determination of meloxicam in liposomes using high-performance liquid chromatography-ultraviolet (HPLC-UV). Chromatographic separation was carried out on an Ascentis RP amide C16 column selecting a mobile phase composed of acetonitrile-0.3% formic acid solution (40:60, v/v) adjusted at pH 2.8. The mobile phase flow rate selected was 0.5 mL min−1 and UV detection at 355 nm. Piroxicam was chosen as internal standard. All the analyses were performed at temperatures of 40.0 ± 0.5°C. The calibration curve was linear over the range 18–420 ng mL−1. Relative standard deviation (RSD) for precision was <1.03%. Accuracy ranged between 98.53% and 101.41% with RSD lower than 1.5%. LOD and LOQ were 5 ng mL−1 and 15 ng mL−1, respectively. The method was simple, rapid, and easy to apply, making it very suitable for routine analysis of meloxicam in liposomes. The method could also be used with reliability for the determination of meloxicam in other pharmaceutical dosage forms.

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, linked to a triterpene type of aglycone with four- or five-member ring structures [ 7 ]. There were several studies in analyzing triterpene saponins from various plants using high-performance liquid chromatography (HPLC) [ 8 , 9 ]. For example, reversed-phase

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molecules by reversed-phase liquid chromatography. Anal. Chim. Acta , 399 , 249–258. Li J.W. Evaluation of trifluoroacetic acid as an ion-pair reagent in the separation of small

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derivatization process of silica supports. These silanols are negatively charged within the pH range commonly used in reversed-phase liquid chromatography (2.5–7.5) and can additionally interact with cationic compounds by ion-exchange interaction. Ion

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1 Introduction The use of surfactants as mobile phase additives in reversed phase liquid chromatography (RPLC) has been growing fast over the last decade. Retention behavior in RPLC depends on partitioning between the

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1 Introduction The use of surfactants as mobile phase additives in reversed phase liquid chromatography (RPLC) has been growing fast over the last decade. Retention behavior in RPLC depends on partitioning between the hydrophobic stationary phase

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Abstract  

An analytical technique using reversed-phase liquid chromatography has been developed for the determination of urea at quantities as low as 1 ng to quantitate the amount of non-labelled urea produced during the synthesis of no-carrier-added {11C}urea starting from11CN. As a result, the specific activity of the {11C} urea thus prepared was calculated to be as high as 3.5±0.8 Ci/mol.

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A simple, selective, and precise stability-indicating reversed-phase liquid chromatographic method was developed and validated for the determination of nilotinib. Nilotinib was subjected to acid and alkali hydrolysis, oxidation, thermal, and photo-degradation. The degradation products were well separated from the pure drug. The method was based on isocratic elution of nilotinib and its degradation products on reversed phase C18 column (100 mm × 4.6 mm, 3.5 μm) — Zorbax Eclipse Plus using a mobile phase consisting of 10 mM KH2PO4:acetonitrile (54.5:45.5%, v/v) at a flow rate of 1 mL min−1. Quantitation was achieved with UV detection at 265 nm. Linearity, accuracy and precision were found to be acceptable over the concentration range of 0.1–80 μg mL−1. The drug was found to be susceptible to acid and base hydrolysis but resistant to oxidation, dry heat degradation, and photodegradation. The proposed method was successfully applied to the determination of nilotinib in bulk and in its pharmaceutical preparation.

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