Special gas chromatographic techniques

The gas chromatographic technique is explained on the basis of a physical process with correlations to distillation,liquid-liquid extraction, countercurrent distribution, and other separation techniques to give the reader a better appreciation of the basic process of chromatography. Explanation of fundamentals is followed by chapters on columns and column selection, theory and use of detectors, instrumentation necessary for a gas chromatographic system, techniques used for qualitative and quantitative analyses, and data reduction and readout. Subsequent chapters cover specialized areas in which gas chromatographic literature is more scattered and data collection and evaluation are more important. 

Gas chromatographic techniques can be specially adapted for the specific detection of volatile P compounds. They utilise a specially modified flame ionisation detector known as a nitrogen-phosphorus detector (NPD), and can detect quantities of P down to 10 g/mL. This method has been particularly successful for trace pesticide determination and is now widely employed for other types of phosphorus compound. Gas chromatography, combined with induced chemiluminescence, has been adapted to detect quantities of PH3 and PMcj down to about 1 pg [38]. 

A Gas Chromatographic Technique for Determination of Blood Flow and Metabolism in Individual Organs (with Special Reference to the Heart)... 

Camphor has been determined by Baines and Proctor in a number of essential oils and pharmaceutical preparations using a gas chromatographic technique. It was necessary, for some of the samples, to use a special injection system (see p. 877) in order to prevent non-volatile materials in the samples from entering the column. The apparatus employed a thermal... 

Activity coefficients at infinite dilution, of organic solutes in ILs have been reported in the literature during the last years very often [1,2,12,45,64, 65,106,123,144,174-189]. In most cases, a special technique based on the gas chromatographic determination of the solute retention time in a packed column filled with the IL as a stationary phase has been used [45,123,174-176,179,181-187]. An alternative method is the "dilutor technique" [64,65,106, 178,180]. A lot of y 3 (where 1 refers to the solute, i.e., the organic solvent, and 3 to the solvent, i.e., the IL) provide a useful tool for solvent selection in extractive distillation or solvent extraction processes. It is sufficient to know the separation factor of the components to be separated at infinite dilution to determine the applicability of a compound (a new IL) as a selective solvent. 

Characterization. A major emphasis has been placed on the use of small samples of polymer. This enables 1) a variety of different types of experiments such as G value determination and 2) a sufficient number of experiments to enable statistical evaluation of derived values, to be performed on small amounts of polymer produced in the laboratory, as in copolymerizations to low conversions (necessary to avoid drifting in composition). Yields of small molecule products were obtained from 10-50 mg samples of polymer utilizing a technique of breaking an ampoule of the irradiated polymer in a specially constructed injection system in a gas chromatograph (2). 

Ranid instrumental techniques were used to elucidate off-flavor problems in raw and processed rice products, raw and roasted peanuts, and corn-soy food blends. Less than a gram of the solid material was secured in a standard or special injection port liner of the gas chromatograph. Then, the volatiles from the sample were steam distilled in situ and identified by combined gas chromatography/mass spectrometry. 

A special application of gas chromatographic determination of nicotine in biological fluids is its determination in the breast fluid of non-lactating women. By using a combination of gas chromatography, mass spectrometry and a selected ion recording technique, Petra-47... 

Gas chromatography is one of the most widely used techniques for qualitative and quantitative analysis. The photo shows a capillary column useful in gas chromatographic determinations at temperatures exceeding 400°C. Such high-temperature applications require special stationary phases and tubing that will not decompose. The column shown has tubing made from stainless steel. 

Clearly, the preferred method to use for the analysis of phosgene depends upon the particular application to hand. For routine use in the laboratory, for monitoring the ambient air, impregnated paper strips and Dra ger tubes can be recommended as both reliable and easy to use. On the plant, automatic methods for continuous analysis would be appropriate, and one of the electrical or automated spectroscopic techniques would be suitable. For accurate measurement of very low (p.p.b.) concentrations however, a gas chromatographic procedure using one of the special detectors is most suitable. 

The gas chromatograph can be used for meaningful analysis only after the appropriate column and detector have been selected. However, there is still an important aspect of gas chromatographic analysis that needs to be mentioned. This involves the introduction of the sample into the column. Sample introduction is achieved by using special injectors. There are five techniques to introduce sample into the column. 

---