Injection port temperature

If the injection port temperature is too high, the sample will partially decompose but the GC peak for the intact material will be sharp and rK will not be affected. However, if the sample decomposes on the column the tR will vary and the observed peak will be broad. For normal stable samples, the injection port temperatures should be in the range of 150-280°. 

Injection 5 pi of petroleum ether solution Injection port temperature 250°C Detector temperature ... 

Injection port temperature Detector temperature Helium flow rate Hydrogen flow rate ... 

Column temperature Injection port temperature Detector Gas flow rates... 

Gas chromatograph Injection port Temperature Carrier gas Flow rate Column... 

Injection port temperature Interface temperature Detector... 

When the column temperature is set to a near ambient temperature, external air is brought into the oven via a computer-controlled flap, providing rigid temperature control stability. (The lowest controllable column temperature is 24°C when the ambient temperature is 18°C and the injection port temperature is 250°C. The temperature fluctuation is less than 0.1 °K even when the column temperature is set at 50°C. 

Glass column, 1.8m long, 6mm dia., packed with 3% OV-1 on Chromosorb W 80-100 mesh carrier gas, 70ml nitrogen min-1 injection port temperature, 150-C temperature programme, initial 50°C for 2min, programmed at 15°C min-1, until 150°C sample trap temperature, 80-100°C... 

The purity of the infrared spectroscopy or by gas chromatography using an NMPN (3-nitro-3-methylpimelonitrile) column. A low injection port temperature is desirable (<200°). 

Bromonitromethanes are substantially increased in formation with the use of pre-ozonation before chlorine or chloramine treatment, and concentrations up to 3 pg/L individually have been reported [11,12]. Laboratory-scale formation studies indicate that nitrite may play a role in the formation of the nitro group in these DBFs [40]. Tribromonitromethane (bromopicrin) and other trihalonitromethanes (which include bromodichloro- and chlorodibromonitromethane) require particular analytical conditions for their analysis. These compounds are thermally unstable and decompose under commonly used injection port temperatures during gas chromatography (GC) or GC/mass spectrometry (MS) analysis [41]. 

Chlorotrifluoromethyl aniline (no. 73.) was found in the sediment samples. This compound is used as a reactant with chloro-aniline (no. 72) in the preparation of 4,4 -dichloro-3-(trifluoromethyl)-carbanilide, a disinfectant. Two other related compounds also found in some of the sediments were chlorophenyl isocyanate (no. 74) and chloro(-trifluoromethyl)phenyl isocyanate (no. 75). This suggests that some of the 4,4 -dichloro-3-(trifluoromethyl)-carbanilide may, in fact, exist in the sediment extracts but is decomposed in the injection port of the gas chromatograph, since it is very doubtful that the easily hydrolyzable isocyanates exist as such in the sediments. To strengthen this hypothesis some 3,4,4 -trichlorocarbanilide [none of the 4,4 -dichloro-3-(trifluorome-thyl)-carbanilide was available] was analyzed by GCMS. The injection port temperature was 300°C. As expected, none of the parent compound eluted from the column. However, mass spectra were obtained for chlorophenyl isocyanate, dichlorophenyl isocyanate, chloroaniline, and dichloroaniline. The presence of the carbanilides themselves (no. 76, 77, 78) was confirmed with the help of HPLC and mass spectral identification. 

GC and GC-MS Analyses. Glass capillary columns were prepared in our laboratories as described briefly elsewhere (3). Aliquots (l-2 ul) of the PAH fraction dissolved in a small volume of chloroform were injected without stream splitting into the Hewlett Packard 5dk0A gas chromatograph. Injection port temperature was held at 250°C, and the column oven temperature was started at 100°C. Two minutes after injection a multistep temperature program was initiated final temperature was 290°C. Nitrogen was the carrier and make up gas. 

Sometimes thermal decomposition and reaction can be shown by variation of injection port temperature, and possibly column temperature. The only real solution is to operate at as low a temperature as possible and perhaps use "on-column injection. Low-loaded columns sometimes help. Use of glass columns and glass injection port liners often relieve the problem of unwanted thermal degradation and may help in some cases. However, in all cases the precision and accuracy of the quantitative analysis will be affected until a solution is found or until a decision is made to "live with it."... 

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