Gas chromatography conditions

Generally, alkan olamines are analyzed by gas chromatography or wet test methods. Details on gas chromatography conditions are available in the fiterature (1) for packed or glass capillary columns. 

Gas chromatography conditions are as follows Supelco fused silica capillary SPB-1 column (30 m, 0.32-mm ID, 0.25 micrometers df), 100°C initial temperature, 280°C final temperature, 10°C/min. The following retention times were obtained diphenylacetaldehyde (6.7 min), trans-stilbene oxide (7.4 min), Tischenko product (18.2 min). 

Once the gas chromatography conditions are chosen, the next step is to decide how the samples and standards are going to be introduced to the gas chromatograph. Several techniques can be chosen with some being more prac-... 

Gas chromatography conditions. Gaseous pyrolyzate separated on a 10 foot x 1.8 inch o.d. stainless steel column packed with beta,beta -oxydipropionitrile Porasil C Durapak (Waters Associates), 80 to 100 mesh. The carrier gas is argon flowing at the rate of 15 cm 3 min" The temperature of the column oven is initially 90 C 3 min after pyrolysis, the temperature of the column oven is raised to 120 C and maintained there. The flame ionization detector is optimized for fluorocarbons. The complete elution of all fragments takes 30 min. 

Selectivity Because it combines separation with analysis, gas chromatography provides excellent selectivity. By adjusting conditions it is usually possible to design a separation such that the analytes elute by themselves. Additional selectivity can be provided by using a detector, such as the electron capture detector, that does not respond to all compounds. 

Analytical and Test Methods. Gas chromatography is used for the quantitative analysis of malonates. Typical analysis conditions are 5% Reoplex 400 on Chromosorb G 80—100 mesh 2 m, 0.3 cm diameter metal column temperature for column = 120° C detector, 150°C and injector, 120°C. 

Ghlorophenol Analysis. The chlorophenols can be analy2ed by acidimetric titration of the hydroxyl function (50). This overall method yields only an approximate evaluation for mixtures. To analy2e chlorophenol mixtures, gas chromatography has been the reference method used, as it made it possible to separate and quantify the various chlorophenols (51), but this technique can be a source of errors the gem-chlotinated cyclohexadienones that may be present along with the chlorophenols are broken back down iato lighter chlorophenols under the analysis conditions usually employed. 

The purity of a dicyclopentadiene stream may be expressed in terms of DCPD itself or in terms of available CPD monomer. Both analyses are deterrnined by gas chromatography (gc). The first analysis is capillary gc on a nonpolar column. The data from the analysis can be used to calculate the available CPD, assuming that all the DCPD and CPD codimers crack completely. In the second analysis the sample is charged to the gc equipment under temperature conditions (injection port 400°C) that cause essentially complete reaction of the dimers to monomers. 

The irradiation of 2-methoxytropone (A) leads to methyl 4-oxo-2-cyclopentenyl-acetate (D). The reaction can be followed by analytical gas chromatography and two intermediates are observed. These have the structures B and C. Indicate a mechanism by which each of the three successive reactions might occur. The first two steps are photochemical, while the third is probably an acid-catalyzed reaction which occurs under the photolysis conditions. 

Figure 12.8 Mia ocolumn size exclusion chromatogram of a styrene-aaylonitrile copolymer sample fractions ti ansfeired to the pyrolysis system are indicated 1-6. Conditions fused-silica column (50 cm X 250 p.m i.d.) packed with Zorbax PSM-1000 (7p.m 4f) eluent, THF flow rate, 2.0 p.L/min detector, Jasco Uvidec V at 220 nm injection size, 20 nL. Reprinted from Analytical Chemistry, 61, H. J. Cortes et al, Multidimensional chromatography using on-line microcolumn liquid chromatography and pyrolysis gas chromatography for polymer characterization , pp. 961 -965, copyright 1989, with peimission from the American Chemical Society.

An on-line supercritical fluid chromatography-capillary gas chromatography (SFC-GC) technique has been demonstrated for the direct transfer of SFC fractions from a packed column SFC system to a GC system. This technique has been applied in the analysis of industrial samples such as aviation fuel (24). This type of coupled technique is sometimes more advantageous than the traditional LC-GC coupled technique since SFC is compatible with GC, because most supercritical fluids decompress into gases at GC conditions and are not detected by flame-ionization detection. The use of solvent evaporation techniques are not necessary. SFC, in the same way as LC, can be used to preseparate a sample into classes of compounds where the individual components can then be analyzed and quantified by GC. The supercritical fluid sample effluent is decompressed through a restrictor directly into a capillary GC injection port. In addition, this technique allows selective or multi-step heart-cutting of various sample peaks as they elute from the supercritical fluid... 

One example of normal-phase liquid chromatography coupled to gas chromatography is the determination of alkylated, oxygenated and nitrated polycyclic aromatic compounds (PACs) in urban air particulate extracts (97). Since such extracts are very complex, LC-GC is the best possible separation technique. A quartz microfibre filter retains the particulate material and supercritical fluid extraction (SPE) with CO2 and a toluene modifier extracts the organic components from the dust particles. The final extract is then dissolved in -hexane and analysed by NPLC. The transfer at 100 p.1 min of different fractions to the GC system by an on-column interface enabled many PACs to be detected by an ion-trap detector. A flame ionization detector (PID) and a 350 p.1 loop interface was used to quantify the identified compounds. The experimental conditions employed are shown in Table 13.2. 

One of the first examples of the application of reverse-phase liquid chromatography-gas chromatography for this type of analysis was applied to atrazine (98). This method used a loop-type interface. The mobile phase was the most important parameter because retention in the LC column must be sufficient (there must be a high percentage of water), although a low percentage of water is only possible when the loop-type interface is used to transfer the LC fraction. The authors solved this problem by using methanol/water (60 40) with 5% 1-propanol and a precolumn. The experimental conditions employed are shown in Table 13.2. 

A small forerun of 2,4-pentanedione, b p 32-100° (19 mm.), is obtained The purity of the product may be demonstrated by gas chromatography on a 2-ft column packed with silicone gum rubber (F and M Scientific Co, Avondale, Pennsylvania) programmed linearly from 100° to 300° The chromatogram obtained is a single sharp peak The three conceivable impurities, 2,4-pentanedione, 3-butyl 2,4-pentanedione, and 6,8-tridecanedione, would have been observed under these conditions if they had been present. 

The quantitative determination of a component in gas chromatography using differential-type detectors of the type previously described is based upon meas urement of the recorded peak area or peak height the latter is more suitable in the case of small peaks, or peaks with narrow band width. In order that these quantities may be related to the amount of solute in the sample two conditions must prevail ... 

Maximum benefit from Gas Chromatography and Mass Spectrometry will be obtained if the user is aware of the information contained in the book. That is, Part I should be read to gain a practical understanding of GC/MS technology. In Part II, the reader will discover the nature of the material contained in each chapter. GC conditions for separating specific compounds are found under the appropriate chapter headings. The compounds for each GC separation are listed in order of elution, but more important, conditions that are likely to separate similar compound types are shown. Part II also contains information on derivatization, as well as on mass spectral interpretation for derivatized and underivatized compounds. Part III, combined with information from a library search, provides a list of ion masses and neutral losses for interpreting unknown compounds. The appendices in Part IV contain a wealth of information of value to the practice of GC and MS. 

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. 

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