Search results for "performance"
showing 10 items of 4457 documents
Development and validation of RP-HPLC method for the quantitative estimation of αs1-genetic variants in goat milk
2013
A high-performance liquid chromatographic (HPLC) method was developed and validated for separation and quantification of the most common genetic variants of as1-casein in goat’s milk, to evaluate the effect of as1-casein polymorphisms on casein content. Chromatography was carried out by binary gradient technique on a reversed-phase C8 Zorbax column and the detection was made at a wavelength of 214 nm. The procedure was developed using individual raw milk samples of Girgentana goats. For calibration experiments, pure genetic variants were extracted from individual milk samples of animals with known genotypes, considering that commercial standards for goat genetic variants were not available.…
Determination of Phenols from Automobile Exhaust by Means of High-Performance Liquid Chromatography (HPLC)
1981
Abstract The paper describes a procedure to determine ten representative phenols (phenol, m-, p-, o-cresol, 2,4-, 2,6-, 3,4-, 3,5-xylenol, 2,3,6-, 2,4,6-trimethylphenol) in engine exhaust. Sampling was performed by a conventional Grimmer device. A sample of the water condensate collected was extracted with ether. After concentration of the ether extract phenols were isolated from other interfering compounds by stepwise elution on a Lobar column packed with LiChroprep Si 60 under controlled conditions. Relative recovery of the majority of reference phenols ranged from 90-100%. Separation of phenols into individual components was performed on polar packings as well as on Reverse Phase packing…
High-performance liquid chromatographic determination of Maillard compounds in store-brand and name-brand ultra-high-temperature-treated cows' milk.
2000
Furosine and furfural products of the Maillard reaction are used as specific indicators of the effect of heating treatments on milk quality. Their contents were measured in representative samples of store- and name-brand ultra-high-temperature-treated milks using RP-HPLC with UV detection. Furosine contents ranged from 40.32 to 50.67 and from 65.48 to 310.58 mg/100 g protein in name- and store-brand milks, respectively. Of the furfurals, only hydroxymethylfurfural was detected. The free hydroxymethylfurfural contents of store-brand milks ranged from 0.22 to 1.70 mg/100 g protein. Total hydroxymethylfurfural contents ranged from 0.29 to 0.41 and from 0.72 to 2.21 mg/100 g protein, for name- …
An automated on-line multidimensional HPLC system for protein and peptide mapping with integrated sample preparation.
2002
A comprehensive on-line two-dimensional 2D-HPLC system with integrated sample preparation was developed for the analysis of proteins and peptides with a molecular weight below 20 kDa. The system setup provided fast separations and high resolving power and is considered to be a complementary technique to 2D gel electrophoresis in proteomics. The on-line system reproducibly resolved approximately 1000 peaks within the total analysis time of 96 min and avoided sample losses by off-line sample handling. The low-molecular-weight target analytes were separated from the matrix using novel silica-based restricted access materials (RAM) with ion exchange functionalities. The size-selective sample fr…
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…
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…
Homochiral Metal-Organic Frameworks for Enantioselective Separations in Liquid Chromatography
2020
Selective separation of enantiomers is a substantial challenge for the pharmaceutical industry. Chromatography on chiral stationary phases is the standard method, but at a very high cost for industrial-scale purification due to the high cost of the chiral stationary phases. Typically, these materials are poorly robust, expensive to manufacture, and often too specific for a single desired substrate, lacking desirable versatility across different chiral analytes. Here, we disclose a porous, robust homochiral metal–organic framework (MOF), TAMOF-1, built from copper(II) and an affordable linker prepared from natural l-histidine. TAMOF-1 has shown to be able to separate a variety of model…