Search results for " High pressure liquid"
showing 10 items of 705 documents
Determination of acetazolamide in human urine samples by reversed-phase high-performance liquid chromatography in the presence of xanthines.
1992
A simple, rapid and selective high-performance liquid chromatographic assay for the determination of acetazolamide in urine samples is described. After extraction with ethyl acetate, the drug is chromatographed on an HP-Hypersil ODS-C18 column with a mobile phase of acetonitrile-phosphate buffer (pH 3) and ultraviolet detection at 275 nm. The efficiency of the extraction, the linearity and the reproducibility of the method permit the evaluation of acetazolamide urinary excretion a long time after its administration.
Use of triacylglycerol profiles established by high performance liquid chromatography with ultraviolet–visible detection to predict the botanical ori…
2011
A method for the determination of triacylglycerols (TAGs) in vegetable oils from different botanical origins by HPLC with UV–vis detection has been developed. Using a core-shell particle packed column (C18, 2.6 micron), TAG separation was optimized in terms of mobile phase composition and column temperature. Using isocratic elution with acetonitrile/n-pentanol at 10 °C, excellent efficiency with good resolution between most of the TAG peak pairs, within a total analysis time of 15 min, was achieved. Using mass spectrometry detection, a total of 15 peaks, which were common to oils of six different botanical origins (corn, extra virgin olive, grapeseed, hazelnut, peanut and soybean) were iden…
Characterization of the alcoholic fraction of vegetable oils by derivatization with diphenic anhydride followed by high-performance liquid chromatogr…
2008
Abstract Aliphatic and triterpene alcohols present in vegetable oils have been identified and determined by HPLC using UV–vis and MS detection after previous derivatization with diphenic anhydride. The alcoholic fraction was obtained by saponification, extraction and TLC (according to the European Union official procedure). Derivatization was performed in tetrahydrofuran in the presence of suspended grinded urea, which increases the reaction rate and yield. Derivatized extracts were chromatographed on a C8 column using gradient elution with acetonitrile/water mixtures containing 0.1% acetic acid, with UV–vis followed by negative-ion mode MS detection. Using linear discriminant analysis of t…
Comparative modelling study on enantioresolution of structurally unrelated compounds with amylose-based chiral stationary phases in reversed phase li…
2020
[EN] Polysaccharide-based chiral stationary phases (CSPs) are the most used chiral selectors in HPLC. These CSPs can be used in normal, polar organic and aqueous-organic mobile phases. However, normal and polar organic mobile phases are not adequate for chiral separation of polar compounds, for the analysis of aqueous samples and for MS detection. In these situations, reversed phase conditions, without the usual non-volatile additives incompatible with MS detection, are preferable. Moreover, in most of the reported chiral chromatographic methods, retention is too large for routine work. In this paper, the chiral separation of 53 structurally unrelated compounds is studied using three commer…
High-performance liquid chromatographic separation of modified and native melittin following transglutaminase-mediated derivatization with a dansyl f…
1991
Abstract The 26-amino acid linear, amphiphilic peptide melittin was enzymatically modified with the fluorescent probe monodansylcadaverine using guinea pig liver transglutaminase and a fluorescent derivative of stoichiometry 1:1 was obtained. Reversed-phase and size-exclusion high-performance liquid chromatographic modes were tested in order to resolve the labelled peptide and native species. The influence of several operational variables was analysed and the elution conditions were optimized so that a satisfactory resolution could be achieved in both instances in a rapid, easy manner. Both chromatographic modes offer the possibility of accurate monitoring of the time course of the enzyme-m…
The (2'-5')Oligoadenylate Synthetase is Present in the Lowest Multicellular Organisms, the Marine Sponges. Demonstration of the Existence and Identif…
1995
We have proved the presence of (2'-5')oligoadenylates [(2'-5')An] and oligoadenylate synthetase [(2'-5')An synthetase] in the marine sponge Geodia cydonium. (2'-5')An isolated from sponge crude extract competed with authentic (2'-5')An for binding to polyclonal antiserum against (2'-5')An. HPLC analysis revealed the presence of nucleotides eluting with molecular markers for (2'-5')A oligomers. The biological activity of sponge (2'-5')An was demonstrated by inhibiting the protein biosynthesis in rabbit reticulocyte lysate. The activity of the (2'-5')An synthetase, present in crude sponge extract, was found to be high compared to that in mammalian interferon-treated cell extract. The (2'-5')A…
Sequential window acquisition of all theoretical fragments versus information dependent acquisition for suspected-screening of pharmaceuticals in sed…
2019
The aquatic ecosystems are dynamic environments often affected directly or indirectly by a myriad of anthropogenic contaminants that need to be properly identified. In this study, liquid chromatography-quadrupole time-of-flight mass spectrometry (LC-QqTOF-MS) suspected-screening was applied to mussels and riverine sediment both, non-spiked and spiked with a mixture of 32 pharmaceuticals. Three data acquisition methods –sequential window acquisition of all theoretical fragment-ion spectra (SWATH), in fix (FSWATH) and variable (VSWATH) window modes and Information Dependent Acquisition (IDA)– were compared to determine the most suitable acquisition technique. The results obtained in the spike…
Evaluation of mycotoxins and their metabolites in human breast milk using liquid chromatography coupled to high resolution mass spectrometry
2014
Humans can be exposed to mycotoxins through the food chain. Mycotoxins are mainly found as contaminants in food and could be subsequently excreted via biological fluids such as urine or human breast milk in native or metabolised form. Since breast milk is usually supposed as the only food for new-borns, the occurrence of mycotoxins in thirty-five human milk samples was evaluated by a newly developed method based on QuEChERS extraction and UHPLC-HRMS detection. The method described here allows the detection of target mycotoxins in order to determine the quality of this initial feeding. The method has been fully validated, with recoveries ranging from 64% to 93% and relative standard deviatio…
Analysis of sterols by high-performance liquid chromatography/mass spectrometry combined with chemometrics
2006
A newly developed high-performance liquid chromatography/mass spectrometry (HPLC/MS) method has been successfully used to analyze plasma concentrations of various phytosterols (cholestanol and beta-sitosterol) and cholesterol metabolites (desmosterol and lathosterol). This was based on an unusual solvent combination of water/methanol vs. methanol/acetone/n-hexane applied on a Purospher Star RP-18e (125 x 2 mm, 3 microm) column, which proved excellent for the separation, identification and quantification of plasma sterols. Simple solid-phase extraction preparation of plasma samples was performed, followed by the developed fast and robust HPLC separation. Results on four groups of people were…
Physico-Chemical Stability of Admixtures of Vinflunine Used in Clinical Practice.
2021
Procedure of administration of vinflunine is complex and consists of an Y-site injection with fluid at different speeds. Dose is diluted with 100 mL of 0.9% sodium chloride or 5% glucose and infused with half of the 500 mL bag of the fluid over 20 min; after that, the remaining fluid is administered at 300 mL/h. In this study, chemical stability and physical compatibility of vinflunine diluted with in 500 mL of both fluids were evaluated to simplify the administration procedure (infusion of mixture on 20 min followed by 250 mL of fluid at 300 mL/h). Physical compatibility and chemical stability were evaluated at two temperatures and protected from and exposed to light. Physical compatibilit…