Vaporization gas chromatography

Vaporization Gas-Chromatography/Mass-Spectrometry Vaporization gas-chromatography/mass-spectrometry (Vap GC/MS) is a technique developed at MDRL speciHcally to analyze for trace compounds in an intractable matrix (12). 

Vaporization Gas Chromatography and Mass Spectrometry of Aged Resin The... 

Grayson et al. (10) investigated untreated, vacuum-baked at 120°C, and fractionally reprecipitated PS. They analyzed the various samples for indigenous volatile content by vaporization-gas chromatography/mass spectrometry (33,36,37) and found that fractional reprecipitation was the only effective method to remove the volatile fraction from PS. Further, stress MS experiments with PS samples prepared from the fractionally reprecipitated polymer evolved only a trace of styrene monomer. 

Great investment in the development of gas chromatography with volatile modifier (or in vapor gas chromatography) was undertaken by Parcher and co-workers [75-78]. 

Brossa, L. et al.. Determination of endocrine-disrupting compounds in water samples by online solid-phase extraction-programmed-temperature vaporization-gas chromatography-mass spectrometry, /. Chromatogr. A, 998,41, 2003. 

Fernandez-Gonzalez V, Muniategui-Lorenzo S, Lopez-Mahia P, Prada-Rodriguez D (2008) Development of a programmed temperature vaporization-gas chromatography-tandem mass spectrometry method for polycychc aromatic hydrocarbons ancilysis in biota samples at ultratrace levels. J Chromatogr A 1207 136-145... 

For simple FI, the substance to be mass measured is volatilized by heating it close to the emitter so that its vapor can condense onto the surface of the electrode. In this form, an FI source can be used with gas chromatography, the GC effluent being passed over the emitter. However, for nonvolatile and/or thermally labile substances, a different approach must be used. 

Gas chromatography (GC) deals with volatile substances that can be vaporized into a gas stream. Liquid chromatography (LC) concerns mostly nonvolatile substances dissolved in a liquid stream. 

Charcoal Tubes Reference has been made earlier to adsorption, which is the property of some solid materials, such as activated charcoal, to physically retain solvent vapors on their surfaces. In environmental health testing, the adsorbed vapors are removed, generally with a solvent, in a laboratory. The solvent is then analyzed by physical methods (gas chromatography, etc.) to determine the individual compounds whose vapors, such as benzene, were present in the sampled air. Industrial atmospheric samples can be collected in small glass tubes (4 mm ID) packed with two sections of activated charcoal, separated and retained with fiberglass plugs. To obtain an air sample, the sealed ends of the tube are broken off, and air is drawn through the charcoal at the rate of 1 liter per minute by means... 

Together with the techniques described above, other techniques using hot injectors for the transfer of large-volumes in capillary gas chromatography have been developed. Transfer of large-volume solvents in a programmed temperature vaporizing... 

E. C. Goosens, D. de Jong, G. J. de Jong and U. A. Th Brinkman, Reversed-phase liquid cliromatography coupled on-line with capillary gas chromatography. II. Use of a solvent vapor exit to ina ease introduction volumes and introduction rates into the gas cliromato-graplT, J. Microcolumn Sep 6 207-215 (1994). 

The quasi-isostatic method is a variation of the isostatic method. In this case at least one chamber is completely closed, and there is no connection with atmospheric pressure. However, there must be a difference in penetrant partial pressure or a concentration gradient between the two cell chambers. The concentration of permeant gas or vapor that has permeated through into the lower-concentration chamber can be quantified by a technique such as gas chromatography (2). 

Alkanes and Alkenes. For this study, C150-1-01 and C150-1-03 were tested under primary wet gas conditions with ethylene, ethane, propylene, and propane being added to the feed gas. This study was made in order to determine whether these hydrocarbons would deposit carbon on the catalyst, would reform, or would pass through without reaction. The test was conducted using the dual-reactor heat sink unit with a water pump and vaporizer as the source of steam. All gas analyses were performed by gas chromatography. The test was stopped with the poisons still in the feed gas in order to preserve any carbon buildup which may have occurred on the catalysts. 

As sulfonic acid cannot be vaporized, its determination by the direct gas chromatography (GC) method is not possible. To enable determination by GC, the reactivity of the S03H group is used the esterification of the S03H group with diazomethane via acid chloride is one way to transfer the sulfonic acid to volatile compounds. By conversion of the sulfonic acid with phosphoric acid at 200-210°C, the S03H group is cleaved and the hydrocarbons are obtained [184-186]. 

The same samples, after a pretreatment in flowing oxygen (10%) at 625 K, were used as catalysts for the oxidative dehydrogenation of ethanol and methanol in the same reactor. The reaction mixture consisted of O2 (3 or 5%), methanol vapor (3%) or ethanol vapor (5%) and He (balance), all delivered by Tylan mass flow controllers or vaporizer flow controllers. Products were analyzed by gas chromatography. The catalysts exhibited no induction period and their activities were stable over many days and over repeated temperature cycles. 

Bloom NS, Fitzgerald WF. 1988. Determination of volatile mercury species at the picogram level by low temperature gas chromatography with cold-vapor atomic fluorescence detection. Anal Chim Acta 208 151-161. 

The following physico-chemical properties of the analyte(s) are important in method development considerations vapor pressure, ultraviolet (UV) absorption spectrum, solubility in water and in solvents, dissociation constant(s), n-octanol/water partition coefficient, stability vs hydrolysis and possible thermal, photo- or chemical degradation. These valuable data enable the analytical chemist to develop the most promising analytical approach, drawing from the literature and from his or her experience with related analytical problems, as exemplified below. Gas chromatography (GC) methods, for example, require a measurable vapor pressure and a certain thermal stability as the analytes move as vaporized molecules within the mobile phase. On the other hand, compounds that have a high vapor pressure will require careful extract concentration by evaporation of volatile solvents. 

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