Liquid chromatography basic system

In order to design the appropriate liquid chromatography separation system, it is necessary to nnderstand on molecular level some basic principles and tendencies of the processes taking place in the chromatographic column. Above processes resnlt in differences in retention of sample constituents to allow their mutual separation. Extent of retention of macromolecules within colutim reflects the volume of mobile phase needed for their elution, their abovementioned retention volume, V. For the sake of simplicity, let us consider constant overall experimental conditions that is the elnent flow rate, temperature and pressure drop. The latter two parameters are dictated not only by the inherent hydrodynamic resistance of colunm that is inflnenced by the eluent viscosity, size and shape of packing particles but also by the sample viscosity, which may be rather high in polymer HPLC. Further, only one variable molecular characteristic of separated macromolecules will be... 

Enzyme linked electrochemical techniques can be carried out in two basic manners. In the first approach the enzyme is immobilized at the electrode. A second approach is to use a hydrodynamic technique, such as flow injection analysis (FIAEC) or liquid chromatography (LCEC), with the enzyme reaction being either off-line or on-line in a reactor prior to the amperometric detector. Hydrodynamic techniques provide a convenient and efficient method for transporting and mixing the substrate and enzyme, subsequent transport of product to the electrode, and rapid sample turnaround. The kinetics of the enzyme system can also be readily studied using hydrodynamic techniques. Immobilizing the enzyme at the electrode provides a simple system which is amenable to in vivo analysis. 

J.C. Kraak, H.H. van Rooij, and J.L.G. Thus, Reversed-phase ion-pair systems for the prediction of n-octanol/water partition coefficients of basic compounds by high-performance liquid chromatography , J. Chromatogr., 1986, 352,455. 

In many aspects, the behavior of macromolecules substantially differs from the low-molar-mass substances. Therefore, it is necessary to briefly define the basic terms and explain the most important featnres of high-molar-mass systems related to liquid chromatography. To make the understanding as easy as possible, numerous simplifications have been adapted. This section is not intended for experts in polymer science and technology. 

On-line coupling between a gas chromatograph and an atomic spectrometry detector is fairly simple. Typically, the output of the CG capillary column is connected to the entrance of the atomisation-ionisation system simply via a heated transfer line. When separation is performed by liquid chromatography (EC), the basic interface is straightforward a piece of narrow-bore tubing connects the outlet of the EC column with the liquid flow inlet of the nebuliser. Typical EC flow rates of 0.5-2 ml min are within the range usually required for conventional pneumatic nebulisation. 

Since the 1960s, considerable efforts have been devoted worldwide to develop viable An(III)/Ln(III) separation systems, either by liquid-liquid extraction, precipitation, or ion-exchange chromatography. These systems have been regularly reported in comprehensive reviews covering various issues of actinide and lanthanide separations, such as the basics of actinide solution chemistry in aqueous/... 

Four basic types of elution system are used in high performance liquid chromatography. This is illustrated below by the systems offered by LKB, Sweden. 

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