Search results for "liquid chromatography"
showing 10 items of 942 documents
Determination of several aminoglycoside and macrolide antibiotics in animal tissues by liquid chromatography-electrospray ionization-tandem mass spec…
2008
Statistical Approach for Biomarker Discovery Using Label-Free LC-MS Data: An Overview
2016
The identification of new diagnostic, prognostic, or theranostics biomarkers is one of the main aims of clinical research. Technologies like mass spectrometry (MS) focus on the discovery of proteins as biomarkers and are commonly being used for this purpose. Mass spectrometry consists in the separation by gas of charged molecules, based on their mass-over-charge. Liquid chromatography coupled to tandem mass spectrometry (LC-MS/MS) first involves a separation by liquid chromatography (LC) followed by mass spectrometry in the MS and MS/MS modes.
Development of a liquid chromatography–tandem mass spectrometry for the determination of enniatins in biological samples from Wistar rats
2014
Pesticides (New Generation) and Related Compounds, Analysis of
2017
Miscellaneous pesticides and related compounds comprise substances that can neither be included in the classical chemical category of pesticides nor classified by their mode of action. They are a heterogeneous group of substances, the most representative of which are macrocyclic lactones, chloronicotinyls, tetranortriterpenoids, ammonium quaternary salts, dinitroanilines, acetamides, oximes, triazoles, and pyridine-based molecules. The pesticides covered in this article have hardly changed in the last years. However, their analytical determination has undergone significant improvements. This article provides a well-defined and critical compilation of the sample treatment and clean-up proced…
The application of porous silica layers in open tubular columns for liquid chromatography
1987
Two methods to realize a porous retentive silica layer on the inner wall of 10–25 µm fused silica capillaries for OTLC, etching and precipitation of silica from solution, have been investigated. Etching of the fused silica capillaries with 1M KOH, creates an activated surface, but the capacity of the silica layer is too small to serve as retentive layer in OTLC. Better prospects are offered by the precipitation of silica from a solution of polyethoxysiloxane, dynamically coated on the inner wall of the fused silica capillary. It appears to be possible to deposite a porous silica layer up to 0.8 µm thick (in a 25 µm capillary) by this method, which seems to be suitable for liquid-solid an dy…
Error analysis and performance of different retention models in the transference of data from/to isocratic/gradient elution.
2003
The transferability of retention data among isocratic and gradient RPLC elution modes is studied. For this purpose, 16 beta-blockers were chromatographed under both isocratic and gradient elution with acetonitrile-water mobile phases. Taking into account the elution mode where the experimental data come from, and the mode where the retention should be predicted, the following combinations are possible: isocratic predictions from (i) isocratic or (ii) gradient experimental designs; and gradient predictions from (iii) isocratic or (iv) gradient data. Each of these possibilities was checked using three retention models that relate the logarithm of the retention factor: (a) linearly and (b) qua…
Column technology in liquid chromatography
2017
This chapter deals with the most important part of the liquid chromatography (LC) system: the column enabling the efficient and fast resolution of complex mixtures. It is divided into seven sections under the overall aspects of manufacture, operation, and evaluation of analytical columns for the user. The first three sections highlight the column design and hardware, followed by a thorough treatment of the properties of microparticulate silica adsorbents as packing material, stationary phases performed by surface functionalization, and the column filling process. Then, the implementation of the column into the LC system is discussed, leading into chromatographic column testing as a C18-bond…
Modelling of retention behaviour of solutes in micellar liquid chromatography
1997
In micellar liquid chromatography (MLC), the resolution for a given multi-component mixture can be optimized by changing several variables, such as the concentrations of surfactant and organic modifier, the pH and temperature. However, this advantage can only be fully exploited with the development of mathematical models that describe the retention and the separation mechanisms. Several reports have appeared recently on the possibilities of accurately predicting the solute retention in MLC. Although the retention and selectivity may strongly change with varying concentrations of surfactant, organic modifier and/or pH, the observed changes are very regular, and are well described by simple m…
Comparison of microextraction procedures to determine pesticides in oranges by liquid chromatography-mass spectrometry.
2002
A liquid chromatographic-mass spectrometric method has been developed for the determination of bitertanol, carbendazim, fenthion, flusilazole, hexythiazox, imidacloprid, methidathion, methiocarb, pyriproxyfen and trichlorfon. Two procedures, based on stir bar sorptive extraction (SBSE) and matrix solid-phase dispersion (MSPD), have been evaluated for the extraction of these compounds in oranges. Their respective advantages and disadvantages are also discussed. The recoveries obtained by MSPD ranged from 47 to 96% and the relative standard deviations (RSDs) ranged from 1 to 15%, whereas with the SBSE method the recoveries were between 8 and 84% and the RSDs between 4 and 16%. Although, the l…
Simultaneous determination of imidacloprid, carbendazim, methiocarb and hexythiazox in peaches and nectarines by liquid chromatography–mass spectrome…
2002
Abstract A liquid chromatographic (LC) atmospheric pressure chemical ionization mass spectrometric (MS) method is described for determining imidacloprid, carbendazim, methiocarb and hexythiazox in peaches and nectarines. The samples were extracted with ethyl acetate and anhydrous sodium sulfate. Recoveries yield for spiking samples were ranged from 64±9% (R.S.D) for carbendazim to 108±14% (R.S.D.) for hexythiazox at the concentration of 0.1 mg kg−1 (n=5). The correlation coefficients were greater than 0.998 over the range between 0.02 and 2 mg kg−1. The limits of quantitation (LOQ) were 0.02 mg kg−1 for all the pesticides. The applicability of the method to detect and quantify imidacloprid,…