Search results for "Llar"
showing 10 items of 3592 documents
Adsorbent phases with nanomaterials for in-tube solid-phase microextraction coupled on-line to liquid nanochromatography
2015
Following the present trends in miniaturization, a methodology that combines on-line In-Tube Solid-Phase Microextraction (IT-SPME) with Liquid Nanochromatography (nano-LC) and UV-vis diode array detection (DAD) was developed. This coupling was achieved by using two interconnected valves (i.e. conventional and micro-automatic valves) in the system of injection. As for IT-SPME, different materials, containing in some cases nanostructures or nanoparticles and in other cases polymeric adsorbent phases immobilized on capillary columns, were tested in order to improve extraction efficiencies of organic compounds; diclofenac was selected as the target analyte. Additionally, the transfer time of th…
In-tube solid-phase microextraction-capillary liquid chromatography as a solution for the screening analysis of organophosphorus pesticides in untrea…
2006
This paper describes a method for the selective screening of organophosphorus pesticides in water. In-tube solid-phase microextraction (SPME) in an open capillary column coupled to capillary liquid chromatography (LC) with UV detection has been used to effect preconcentration, separation and detection of the analytes in the same assembly. For in-tube SPME two capillary columns of the same length and different internal diameters and coating thicknesses have been tested and compared, a 30 cm x 0.25 mm I.D., 0.25 micro m thickness coating column, and a 30 cm x 0.1 mm I.D., 0.1 micro m of coating thickness column. In both columns the coating was 95% dimethylpolysiloxane (PDMS)-5% diphenylpolysi…
Green aspects, developments and perspectives of liquid phase microextraction techniques.
2014
Determination of analytes at trace levels in complex samples (e.g. biological or contaminated water or soils) are often required for the environmental assessment and monitoring as well as for scientific research in the field of environmental pollution. A limited number of analytical techniques are sensitive enough for the direct determination of trace components in samples and, because of that, a preliminary step of the analyte isolation/enrichment prior to analysis is required in many cases. In this work the newest trends and innovations in liquid phase microextraction, like: single-drop microextraction (SDME), hollow fiber liquid-phase microextraction (HF-LPME), and dispersive liquid-liqu…
Analytical potential of mid-infrared detection in capillary electrophoresis and liquid chromatography: a review.
2010
Literature published in the last decade concerning the use of mid-infrared spectrometry as a detection system in separation techniques employing a liquid mobile phase is reviewed. In addition to the continued use of isocratic liquid chromatographic (LC) techniques, advances in chemometric data evaluation techniques now allow the use of gradient techniques on a routine basis, thus significantly broadening the range of possible applications of LC-IR. The general trend towards miniaturized separation systems was also followed for mid-IR detection where two key developments are of special importance. Firstly, concerning on-line detection the advent of micro-fabricated flow-cells with inner volu…
Capillary electrophoretic and extraction conditions for the analysis of Catha edulis FORKS active principles
2013
A capillary electrophoretic method, which allowed the detection and separation of the active principles of Catha edulis, i.e. cathinone, cathine and phenylpropanolamine, was developed. A suitable internal standard (nicotinamide), which permitted the quantification of the analytes reducing the variability of the migration times due to EOF changes, was identified. The analytical method was validated, assessing linearity, sensitivity and repeatability, showing optimal features for the analysis of the vegetable material. Moreover extraction conditions were investigated to achieve the exhaustion of the plant material in the fastest and most efficient way to meet the requirements of the Court.
Capillary electrokinetic fractionation mass spectrometry (CEkF/MS): Technology setup and application to metabolite fractionation from complex samples…
2014
Capillary electrokinetic fractionation (CEkF) is investigated as a new, simple, and robust approach for semipreparative and analytical sample analysis based on pKa -dependant pH-driven electrophoretic mobility. CEkF was optimized with contactless conductivity detection and conducted with 10 kV reverse voltage for 10 min, then coupled on/at-line to ESI/MS. We propose a semi-empirical model with 14 representative compounds based on the correlation between sample/medium pH regulating the partial charge, the electrokinetic loading of the capillary and intensity (I) of analytes. According to the model, an empirical function (I = f (pH)) could be derived to calculate the acid dissociation constan…
Control of propranolol intake by direct chromatographic detection of alpha-naphthoxylactic acid in urine.
2002
A rapid chromatographic procedure with a C18 column, a mobile phase of 0.15 M sodium dodecyl sulfate (SDS)-10% (v/v) 1-propanol at pH 3 (0.01 M phosphate buffer), and fluorimetric detection, is reported for the control of propranolol (PPL) intake in urine samples, which are injected directly without any other treatment than filtration. The peak of PPL was only observed in samples taken a few hours after ingestion of the drug due to its extensive conjugation and metabolisation. The detection of several unconjugated PPL metabolites was therefore considered: desisopropylpropranolol (DIP), propranolol glycol (PPG), alpha-naphthoxylactic acid (NLT) and alpha-naphthoxyacetic acid (NAC). NLT showe…
Micellar liquid chromatography determination of rivaroxaban in plasma and urine. Validation and theoretical aspects.
2019
A Micellar Chromatographic method to determine rivaroxaban in plasma and urine has been developed. The samples were dissolved in the mobile phase (SDS 0.05 M – 1-propanol 12.5%, phosphate buffered at pH 7) and 20 μL directly injected, avoiding the extraction and purification steps. Using a C18 column and running under isocratic mode at 1 mL/min, analyte was eluted without interference from the matrix in <6.0 min. The detection absorbance wavelength was set to 250 nm. The procedure was validated by Food and Drug Administration guidelines in terms of: system suitability, calibration range (0.05–5 mg/L), linearity, sensitivity, robustness, carry-over effect, specificity, accuracy (−11.1 to 4.2…
Determination of triamterene and its main metabolite hydroxytriamterene sulfate in human urine by capillary electrophoresis using ultraviolet absorba…
2002
Abstract Two capillary electrophoresis methods have been developed for the direct determination of triamterene and its main metabolite hydroxytriamterene sulfate in human urine. Analytes were detected using conventional UV detection as well as laser-induced fluorescence (LIF) detection with an HeCd-laser operating at a wavelength of 325 nm. The results of both detection techniques were compared. Indeed, the limit of quantification was eightfold lower using LIF detection (50 ng/ml) in comparison to UV detection (400 ng/ml). As no interference due to endogenous urine compounds was observed, direct urine analysis was feasible. Analysis was very simple and fast—one run could be performed within…
Analytical strategies to determine quinolone residues in food and the environment
2007
23 páginas, 5 figuras, 5 tablas.