Search results for "COLUMN"
showing 10 items of 1301 documents
Thin-layer chromatography of 2-methyl-4-chlorophenoxyacetic acid and its soil metabolites
1980
Abstract The thin-layer chromatography of 2-methyl-4-chlorophenoxyacetic acid, 4-chloro- o -cresol and 3-methyl-5-chlorocatechol and their pentafluorobenzyl derivatives has been studied on silica gel as adsorbent with 19 solvent systems. The best separation of the individual components occurred with toluene-benzene-acetic acid (2:2:1). Chloroform-diethyl ether-toluene (1:1:1) was suitable for the group separation of the pentafluorobenzyl derivatives.
Porous fractal gels: secondary effects in SEC
1992
Abstract The fractal nature of porous silica gels, Spherosil XOA 200 and of a Lichrospher mixture, has been tested through size exclusion chromatography of polystyrene in pure and mixed eluents. Fractal parameters, D f and L , depend on eluent with D f values close to 2.0 for Spherosil and higher than 2.0 for Lichrospher. D f and L changes with eluent have been related to secondary separation effects and partition and adsorption contributions have been evaluated.
Synthesis and characterization of alumina R chemically modified withn-octyl for use as a stationary phase in TLC
2003
A stationary phase for thin-layer chromatography has been prepared by attaching 1-octene to alumina R. This stationary phase has been characterized by elemental analysis, measurement of specific surface area, IR spectroscopy, and by chromatographic testing.
Evaluation of advanced silica packings for the separation of biopolymers by high-perforamnce liquid chromatography
1987
Non-porous monodisperse 1.5-μm silicas were allowed to react with (A) and (B) N-acetylaminopropyltriethoxysilane to generate bonded phases useful in high-performance hydrophobic-interaction chromatography (HIC). Differences in the selectivity were observed between he amide and the ether phase. Peak capacities between 10 and 30 were achieved for several proteins with the amide and ether phase packed into columns of 36 × 8 mm I.D. and elution of the proteins under chromatographic conditions in which the gradient volume, VG, was held constant by varying the gradient time between 20 and 2.5 min and the flow-rate between 0.5 and 4.0 ml/min. The S values derived from the dependences of log k′ on …
Comparative study of capillary electroendosmotic chromatography and electrically assisted gradient nano-liquid chromatography for the separation of p…
2000
Capillary electroendoendosmotic chromatography (CEC), being a hybrid of high-performance liquid chromatography (HPLC) and capillary electrophoresis, offers considerable changes to enhance column efficiency, speed of analysis and additional selectivity as compared to the parent methods. The analytes are driven by the electroendosmotic flow (EOF) and separated by surface-solute interactions as well as by differences in electromigration. In this paper on the separation of peptides on C18 reversed-phase and mixed-mode (sulphonic acid-n-alkyl) packings in CEC and electrically assisted reversed-phase gradient nano-LC are investigated. It is shown that mixed mode packings generate a higher EOF tha…
Comparative study of Zorbax Bio Series GF 250 and GF 450 and TSK-Gel 3000 SW and SWXL columns in size-exclusion chromatography of proteins.
1988
Abstract A reduction of the mean particle diameter of silica-based packings in the size-exclusion chromatography (SEC) of proteins to about 5 μm generates the expected increase in column plate number over the traditional 10 μm SEC columns, as demonstrated for the Zorbax Bio Series GF 250 and GF 450 and TSK-Gel 3000 SWXL columns. The slightly lower column efficiency of the TSK-Gel 3000 SWXL compared with the GF 250 column is compensated by the fact that the phase ratio of the 3000 SWXL column is higher by a factor of two. Hence both columns show nearly the same peak capacity of about 20–30. When the ionic strength of the eluent was changed by varying the salt concentration, the elution volum…
Extraktionschromatographische trennung der freien uroporphyrinisomere i und iii und deren simultane quantitative bestimmung
1968
Abstract Separation and simultaneous quantitative determination of the free uroporphyrin isomers I and III by means of extraction chromatography Separation and quantitative determination of the uroporphyrin isomers I and III in the acid from can be performed simultaneously in the partition system tri-n-butylphosphate/I N hydrochloric acid using columns with a large number of theoretical plates (N) = 300-450). The eluent is passed through a flow cuvette and the transmission is recorded continuously. The transmission peaks of the isomers are digitized and transformed into extinction values. By integrating the extinction peaks, the amount of the uroporphyrins can be evaluated from the correspo…
Micellar liquid chromatography: suitable technique for screening analysis.
2002
The screening capability of micellar liquid chromatography (MLC) is discussed using the reported chromatographic data of several sets of compounds (amino acids, beta-blockers, diuretics, phenethylamines, phenols, polynuclear aromatic hydrocarbons, steroids and sulfonamides) and new results (sulfonamides and steroids). The chromatographic data are treated with an interpretive optimisation resolution procedure to obtain the best separation conditions. Usually, the pH and the concentration of surfactant (sodium dodecyl sulfate, SDS, or cetyltrimethylammonium bromide) for the optimal mobile phase were 2.5-3 and0.12 M, respectively. The nature and concentration of organic solvent depended on the…
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…
Interpretive optimisation of organic solvent content and flow-rate in the separation of β-blockers with a Chromolith RP-18e column
2009
The chromatographic performance of a Chromolith RP-18e column was comprehensively examined for a group of basic drugs (beta-blockers), eluted with isocratic ACN-water mixtures at increasing flow-rate up to 6 mL/min. As the flow-rate increases at fixed mobile phase composition, peak distribution (selectivity) is maintained, but the relative peak widths increase. This reduces the resolution below satisfactory values for closely eluting compounds. With the monolithic column, flow-rate becomes thus an important factor to be optimised, in addition to the mobile phase composition. Since, theoretically, retention factors (k) are independent of the flow-rate, the classical quadratic model relating …