Gas chromatographs capabilities

Procedure (See Chromatography, Appendix IIA.) Use a gas chromatograph capable of split and splitless capillary column injection and equipped with a flame ionization detector and a 25-m x 0.53-mm (id) fused-silica capillary column coated with a 2.0-p.m film of 5% phenyl/95% methylsilicone liquid phase, or equivalent, and a 30-m x 0.32-mm (id) fused-silica capillary column, or equivalent, coated with 1.8-p.m film of (6% cyanopropylphenyl) methylpolysiloxane liquid phase, or equivalent, connected in series, with the first column that was described placed behind the second. Set the injector temperature to 150°, the detector to 250°, and the oven to 40° isothermal. Use helium as the carrier gas at a flow rate of 4.4 mL/min. Set the split flow at a rate of 98 mL/min. 

A new analytical procedure, termed TMAH thermochemolysis, has been used to assess the structure characterization of HS from a variety of samples. Although this procedure has mainly been performed in pyroprobe units at pyrolysis temperatures, it can also be conducted at subpyrolysis temperatures in sealed glass tubes. Therefore, this procedure can be easily implemented in any laboratory having gas chromatographic capabilities, in contrast to other chemolytic or pyrol c procedures. This is a potentially valuable advantage, because it makes the technique readily available to most geochemical laboratories. 

Chromatograph—A gas chromatograph capable of isothermal operation at 130 0.1 C. The gas chromatograph must contain the following ... 

Instrumental Interfaces. The basic objective for any coupling between a gas chromatograph (gc) and a mass spectrometer (ms) is to reduce the atmospheric operating pressure of the gc effluent to the operating pressure in the ms which is about 10 kPa (10 torr). Essential interface features include the capability to transmit the maximum amount of sample from the gc without losses from condensation or active sites promoting decomposition no restrictions or compromises placed on either the ms or the gc with regard to resolution of the components and reliability. The interface should also be mechanically simple and as low in cost as possible. 

The TPD unit was constructed at the Signal UOP Research Laboratory. It Includes a Carle 111 H gas chromatograph with Pd/Ag hydrogen separator, Leeds Northrup temperature programmer, Bascom-Turner 8000 series recorder with data processing and storage capabilities and a custom designed quartz reactor. 

Today s gas chromatograph is a modern, computer-controlled instrument, consisting of an integrated inlet, column oven and detector, with electronically controlled pneumatics and temperature zones. It has an inlet capable of both the split and splitless-injection techniques and it has a highly sensitive (detection limit in the pictogram range) detector... 

Figure 14.3 shows a typical capillary gas chromatograph with the major components labeled. This gas chromatograph set up includes compressed gas tanks for the carrier gas (mobile phase) and any necessary detector gases, an auto-injector that employs a micro-syringe for delivering the necessary small sample volumes and an inlet capable of the... 

Deutsch et al. [96] determined Dursban in sediments by an extraction gas chromatographic procedure which was capable of determining down to O.Olmg kg-1 Dursban using a lOg sample. 

GC-Computer System Nowadays, a large number of data-processing-computer-aided instruments for the automatic calculation of various peak parameters, for instance relative retention, composition, peak areas etc., can be conveniently coupled with GC-systems. A commercially available fairly sophisticated computer system of such type are available abundantly that may be capable of undertaking load upto 100 gas-chromatographs with ample data-storage facilities. In fact, the installation such as multi GC-systems in the routine analysis in oil-refineries and bulk pharmaceutical industries, and chemical based industries have tremendously cut-down their operating cost of analysis to a bare minimum. 

Burtiset al, 1987). Current gas chromatographs have the capability of very complex temperature programs that can minimize the time per run and maximize the resolution of the compounds of interest. The minimum and maximum temperatures are usually the only nonvariable parameters. The solvent usually determines the minimum temperature because it must be volatized for sample introduction. The maximum temperature is determined by the stationary phase, because it may break down at high temperatures, which can result in an elevated baseline of the chromatograph. Thus, the manufacturer recommends a maximum temperature to maximize column life and minimize breakdown. 

Several engineering factors have discouraged more frequent utilization of gas chromatographs aboard aircraft. Laboratory research instruments are large, heavy, and have power requirements that exceed the capabilities of most aircraft. However, smaller, high-quality gas chromatographs are now commercially available and can be easily modified to reduce power consumption. 

The methods used to obtain samples and physically transport them to the gas chromatograph is really no different for GC than for any analytical technique. However, since GC has the inherent capability to do trace analysis, it becomes even more critical to observe the best analytical sampling techniques. Some major areas of concern are obvious. 

Ultraviolet spectrophotometers have been used as gas chromatographic detection systems mainly after condensation of the chromatographic effluent. Systems are capable of detecting naphthalene at 10 8g by scanning every 20 sec from 165 to 220 nm. Use of a monochrometer permits selectivity. Reactions producing chemiluminescence are known. 

The combination of gas chromatograph and mass spectrometer provides a separating and identifying capability not achievable by other means, particularly for very small samples. 

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