Liquid chromatography hardware

Figure 1. Hardware Block Diagram for NBS size-exelusion liquid Chromatography System.

The hardware employed in preparative liquid chromatography typically has the capability for feedback control of the pumps, automatic column switching, column backflushing, recycling, gradient mixing, online pressure, flow rate, UV-absorbance, and temperature monitoring, and automatic pneumatic actuation of fraction collection valves based on time, volume, or UV-absorbance thresholds. These capabilities are afforded by computer control. 

This section describes the various components of an ion chromatography instrument, their function, and some general points for upkeep of the chromatograph. New IC users can use the information to understand how an instrument is built and to recognize the parts of the instrument that may need maintenance. The hardware is similar to that used for high pressure liquid chromatography (HPLC) but does have important differences. Readers who are familiar with HPLC will recognize the similarity and the differences to IC hardware [7-9]. 

This fact, together with the ready availability of well developed hardware for high-performance liquid chromatography (HPLC), makes this technique very attractive for the analysis of non-volatile compounds, especially in routine situations, provided that the separation systems can be combined with a measurement system that retains the resolution obtained and of course also has adequate performance in terms of precision, accuracy, selectivity, dynamic range and especially detection limit. The development of HPLC in the last 10 years vos possible only as a result of the design of measurement systems that fulfilled these demands. 

The analysis of lipids is dominated by chromatographic methods such as gas chromatography (GC) and high-pressure liquid chromatography (HPLC) and some other physical methods such as thermo analysis. Nuclear magnetic resonance (NMR) spectroscopy covers only a small part of lipid analysis. In most cases it is used for qualitative analysis such as structure elucidation of lipids. Unlike the other methods NMR spectroscopy is coupled with computer technology, and its development is as fast as that of computer software and hardware. In 1991 the Nobel Prize for chemistry was given to Professor Ernst for the development of Fourier Transform NMR spectroscopy (FT-NMR). The capabilities of these methods even for the elucidation of the three-dimensional structures of small molecules up to macromolecules are impressive. 

Gas-liquid chromatography has been the focus of much discussion of GC. It is often the case that development of hardware for GC focuses on removing interactions with solid surfaces because the surfaces are considered to be sources of undesirable adsorption sites that contribute to peak asynunetry, especially those in the injection port liner or the chromatographic colunm. However, interactions between a solid substrate and a gas (mobile) phase are also informative. When a solid without a liquid substrate is solely and deliberately used inside the chromatographic column, the techniqne is called gas-solid chromatography (GSC). 

Since the electronic hardware for operating the mass spectrometer was not modified, the current state of the technique allows experiments with O.IV increments for every six seconds. Thns these experiments are currently not compatible with faster preseparation methods, i.e., liquid chromatography. A modification would allow the... 

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