Sample gas chromatography

Preparing a Volatile Sample Gas chromatography can be used to separate analytes in complex matrices. Not every sample that can potentially be analyzed by GG, however, can be injected directly into the instrument. To move through the column, the sample s constituents must be volatile. Solutes of low volatility may be retained by the column and continue to elute during the analysis of subsequent samples. Nonvolatile solutes condense on the column, degrading the column s performance. 

Despite their importance, gas chromatography and liquid chromatography cannot be used to separate and analyze all types of samples. Gas chromatography, particularly when using capillary columns, provides for rapid separations with excellent resolution. Its application, however, is limited to volatile analytes or those analytes that can be made volatile by a suitable derivatization. Liquid chromatography can be used to separate a wider array of solutes however, the most commonly used detectors (UV, fluorescence, and electrochemical) do not respond as universally as the flame ionization detector commonly used in gas chromatography. 

Extracts of muscle tissue are usually sufficiently pure for quantitative gas chromatography at this point, but fat-and-viscera samples require further cleanup. The small sample requirement of the electron capture detector permits a close check on the purification without a significant expenditure of sample. Gas chromatography provides tentative identification at this stage, even in impure samples, and guides the ensuing chromatographic cleanup steps. 

Sample Gas chromatography Steam distil-distillation Total (mg)... 

Opium sample Gas chromatography Value determined Calc. to anhydr. base Other methods... 

Reliable techniques exist for liquid-liquid extraction of ephedrine from alkaline tissue samples. Gas chromatography-mass spectrometry measurement requires pentafluoropropionic acid derivatization. Blood and tissue measurements have been reported in several ephedrine-related deaths, and in clinical trials with therapeutic doses of the drug (Backer et al., 1997). More recently capillary electrophoresis has been used to separate and identify all 10 stereoisomers of the ephedrine family found in nutritional supplements. Chiral discrimination is effected by using hydroxypropyl-P-cyclodextrin (Flurer et al., 1995). 

HPLC analysis of calystegines is somewhat difficult due to their solubility and high polarity, which limit the selection of column packings and solvent mixtures. Moreover, their lack of chromophore excludes spectroscopic methods of detection without pre- or post derivatization of the samples. Gas chromatography on fused silica capillary column coupled with mass spectrometry is the most suitable analytical technique used for the determination of calystegines. However, the high polarity and the nonvolatility of the compounds preclude their analysis without derivatization and numerous derivatization reagents have been tested [9]. 

Measurement of Diphenylhydantoin in 0.1-ml. Plasma Samples Gas Chromatography and Radioimmunoassay Compared... 

Quimby et al (1991) described selective detection of volatile Ni, V and Fe metalloporphyrins in crude oil samples. Gas chromatography connected with an atomic emission detector (AED) was used for the simultaneous detection of Ni 301.2 nm, V 292.4 nm and Fe 302.1 nm. Detection limit for these metals ranged from 0.05-5 pg/sec. The presence of volatile forms of these metals in several crude oil samples was confirmed. 

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