Sample inlets split

GC Analyses, The n-alkanes in the fuel samples were determined with a 100 meter OV-101 wall coated glass capillary column. The inlet split ratio was 50 1, the column oven was temperature programmed from 80 to 240°C, and the inlet temperature was 310°C. The internal standard procedure was used for quantitation. 

The second gc technique determined the individual n-alkanes and 1-alkenes in the pyrolyzed sample. A 100 m wall-coated glass capillary gave the required resolution and the n-alkanes and 1-alkenes stood out as distinct, well resolved peaks. OV-101 or OV-17 wall coatings provide adequate separation. A carrier gas flow of one cc/min was combined with an inlet split ratio of 50 1 and a 310°C injector temperature. The column temperature was raised to 250°C at 4°/min after an 8.0 min initial hold at 80°C. Peak identification was based on retention time matching with n-alkane and 1-alkene standards. 

Figure 6. Selective detection of tetrachloromethane (TCM) contaminations by using SIM mode (measuring conditions Bruker Dallonik GC/MS EM 640S with direct inlet split I 10 direct injection of 0.2 mL gas samples, 30 m HP 5 ms. d, = i)25 mm.. /ih = 0 75 inin). The upper part of the figure incorporates the 3D visualisation of TCM distribution of soil gas (sampling depth 1.80 m combination of IMS and GC-MS data) of part of the contaminated area in the neighborhood of the housing estate...

Sample Met System—The sample inlet sy m must be capable of operating continuously at a temperature up to the maximum column temperature employed. A splitting iqjector is recommended, capable of splitiess or accurate split control in the range of 10 1 to 50 1. An automated gas sampling valve is also recommended. The inlet system must be well conditioned and evaluated frequently for compatibility with trace quantities of reactive sulfur compounds. 

Hot split Sample (usually liquid) passes from syringe into hot inlet rapid vaporisation initial oven temperature not critical small fraction allowed to column (split ratios 1 20 to 1 400) Concentrated samples Narrow 0.1-2 0.01-10... 

Programmed- temperature split Liquid sample from syringe into cold inlet heat programming vaporises sample. Small fraction to column Concentrated samples thermally labile Broad, some focusing required 0.1-2 0.01-10... 

General texts on GC are numerous [118,119] narrow-bore GC was addressed by van Es [120]. Sample introduction techniques and GC inlet systems have been reviewed [25,90] and split/splitless [121] and on-column injection [122] were considered specifically. Stationary phases [123], multiple detection [103], derivatisation [124,125], and quantitative analysis in GC [109] have been described. High-speed GC has recently been reviewed [126]. For a compendium of GC terms and techniques, see Hinshaw [127]. 

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