A chromatograph is an instrument that is used to carry out chromatographic separations. The chromatograph consists of five different entities. The mobile phase supply system, the injection or sampling system, the column and column oven, the detector and the data acquisition and data processing system. In gas chromatography the mobile phase supply system consists of gas tanks, reducing valves, flow controllers and pressure gauges. In liquid chromatography the mobile phase supply system consists of a set of solvent reservoirs, sparged with helium gas to remove dissolved air, a solvent selector valve, a solvent programmer and a high pressure pump. In gas chromatography, the sampling system, in its simplest form, consists of a septum injector and a sampling syringe. In its more sophisticated form, it will include an automatic sampling device that may also be under the chromatograph computer control. Liquid chromatography sampling systems consist of a high pressure sample valve that may also have the sample supplied to the valve from an automatic sampling device. Both gas and liquid chromatography have ovens that are usually temperature programmable, the temperature of the gas chromatographic oven range from 5oC to 350oC and the liquid chromatography oven from about 5oC to 120oC. Gas chromatography usually employs capillary columns whereas packed columns are the most common type of liquid chromatography column. The most common gas chromatography detectors are the flame ionization detector (FID) the Nitrogen Phosphorous Detector (NPD) and the thermal conductivity detector or the hot wire detector (HWD). The three most common liquid chromatography detectors are the UV detector, the fluorescence detector and the refractive index detector (the RI detector). The data acquisition and processing system is very similar for both types of chromatography. They consist of a scaling amplifier and an A/D converter, the output of which is fed to a suitable computer and associated printer. Retention times, retention ratios, peak heights and peak widths are calculated and retention data and quantitative analyses are calculated and then printed out.

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Author: RPW Scott Book:Principles and Practice of Chromatography
Section:Principles   Basic-Chromatograph   Mobile-Phase

The Basic Column Chromatograph A chromatograph consists of five basic units and these units, although possibly designed differently for different systems, are essential for all types of chromatograph, including both gas and liquid chromatographs. The layout of all the five essential units is shown in figure 24. They consists of a mobile phase supply, a sampling system, a column and column oven including a temperature controller and temperature programming system. The temperature controller and

Principles   Basic-Chromatograph   Mobile-Phase

Author: RPW Scott Book:Liquid Chromatography
Section:HPLC   Basic-HPLC

The Basic Liquid Chromatograph The basic liquid chromatograph consists of six basic units. The mobile phase supply system, the pump and programmer, the sample valve, the column, the detector and finally a means of presenting and processing the results. A block diagram of the basic liquid chromatograph is shown in figure 1 Figure 1. The Basic Liquid Chromatograph

HPLC   Basic-HPLC

Author: RPW Scott Book:Gas Chromatography
Section:YES   Modern-GC

majority of the added devices and techniques were suggested or describe in the first three international symposia on gas chromatography held in 1956, 1958 and 1960. These symposia, initially organized by the 'British Institute of Petroleum' have been held every two years ever since 1956 and the meetings have remained the major stimulus for developing the technique and extending its capabilities. However, the majority of the techniques and devices that have been incorporated in the modern chromatograph, were described, reported, or discussed in the first triad of symposia.   The layout of the modern gas chromatograph is shown as a block diagram in figure 1.  

YES   Modern-GC

Author: RPW Scott Book:Capillary Chromatography
Section:Capillary   Apparatus   Gas-Supply

Apparatus for use with Capillary Columns   The apparatus used specifically with capillary columns differs very little from the general gas chromatograph. Capillary columns require particular sampling systems and also have a more restricted range of suitable detectors than those usable with packed columns, but other than that, the capillary gas chromatograph is identical to that used with packed columns. A diagram of the lay out of a gas chromatograph used specifically with capillary columns is shown in figure 5.   Gas Supply   The gas supply incudes the usual gas tank, reducing valve and flow controller; the pressures

Capillary   Apparatus   Gas-Supply

Author: RPW Scott Book:Gas Chromatography
Section:YES   Introduction

Introduction Chromatography, in one of its several forms, is the most commonly used procedure in contemporary chemical analysis and the first configuration of chromatography equipment to be produced in a single composite unit and made commercially available was the gas chromatograph. Gas chromatography was invented by A. J. P. Martin who, with R. L. M. Synge, suggested its possibility in a paper on liquid chromatography published in 1941 (1). Martin and Synge recommended that the liquid mobile phase used in liquid chromatography could be replaced by a suitable gas. The basis for this recommendation was that, due to much higher diffusivities of solutes in gases compared with liquids, the equilibrium processes involved in a chromatographic process (see

YES   Introduction

Author: RPW Scott Book:Gas Chromatography
Section:YES   Gas-Supplies   Pure-Air-Generators.

which is also perceived by some as a serious fire hazard despite the fact that they have been used in laboratories, quite safely for nearly a century. Supplies from Gas Tanks Gasses are stored in large cylindrical tanks fitted with reducing valves that are set to supply the gas to the instrument at the recommended pressure defined by the manufacturers. The cylinders are often situated outside and away from the chromatograph for safety purposes and the gasses are passed to the chromatograph through copper or stainless steel conduits at relatively low pressure. The main disadvantage of gas tanks is their size and weight which makes them difficult to move and replace.   Pure Air Generators. Air generators require an air supply from air tanks or directly from the laboratory compressed air supply. The Packard Zero Air Generator passes the gas through a 0.5 m filter to remove oil and water and finally over a catalyst to remove hydrocarbons. The

YES   Gas-Supplies   Pure-Air-Generators.