Inlet systems splitless inlets

Gas chromatographic analysis starts with introduction of the sample on the column, with or without sample preparation steps. The choice of inlet system will be dictated primarily by the characteristics of the sample after any preparation steps outside the inlet. Clearly, sample preparation has a profound influence on the choice of injection technique. For example, analysts may skip the solvent evaporation step after extraction by eliminating solvent in the inlet with splitless transfer into the column. Sample introduction techniques are essentially of two types conventional and programmed temperature sample introduction. Vogt et al. [89] first described the latter in 1979. Injection of samples, which... 

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]. 

Septum bleed is worse than in split mode because all the flow goes through the column. Most of the splitless inlet systems that are presently available use a vented septum technique to avoid this problem. 

Phthalates can be present in the chromatographic system. The most important contamination is located in the inlet and gas supply system. Split or splitless inlets may contain septa, liners and o-rings that are contaminated with phthalates. Another critical factor is the quality of caps for autosampler vials. These caps can also contain phthalates. 

A HP-5790A gas chromatograph equipped with a split/splitless capillary inlet system and a flame ionization detector are used. A fused-silica capillary column with crosslinked 5% phenyhnethylsilicone gum phase HP-5, 25 m x 0.20 mm i.d., 0.33 pm film thickness, is used. Nitrogen is used as a carrier gas at an inlet pressure of 100 kPa. The oven is operated isothermally at 60°C for 0.5 min after injection, heated at 30°C/min to 200°C, then at 60°C/min to 250°C, and then... 

Programmed-temperature vaporizer, an inlet system designed to perform a temperature programmed injection, a cold injection system for direct liquid injection for split or splitless injection, solvent spHt technique and cryo-enrichment. 

A heated flash vaporization sample inlet system capable of operation in a splitless mode. 

Make-up gas Make-up gas rate Splitless mode Purge off Purge on Purge vent Split vent Sample injection Injector inlet system Detector... 

Gas chromatograph systems are composed of an inlet, carrier gas, a column within an oven, and a detector (O Figure 1-1). The inlet should assure that a representative sample reproducibly, and frequently automatically, reaches the column. This chapter will cover injection techniques appropriate for capillary columns. These include direct, split/splitless, programmed temperature vaporization, and cool on-column injection (Dybowski and Kaiser, 2002). 

Splitless injection is used when the sample is dilute and cannot be introduced into the GC system with stream splitting. In practice, the column temperature is set 10° to 30°C below the boiling point of the solvent at the time of injection. When sample is introduced into the injector inlet, vaporized solvent together with the FAME condense at the beginning of the column along with the carrier gas flow. The condensed solvent plus the stationary phase of the column forms a diluted stationary phase that traps the FAME in it. After the initial sample introduction period, the column temperature is raised to normal operating conditions, and chromatographic separation starts from there. 

Capillary Gas Chromatography (HRGC). Analytical separations were performed on a Varian 3700 GC instrument as well as on a Carlo Erba type 5360 Mega Series gas chromatograph. The Varian 3700 GC system was modified with a hot split/splitless injector and additionally equipped with a commercially available inlet splitter (Gerstel, Mulheim/Ruhr) in order to install two capillary columns... 

Minimal system requirements are a GC equipped with electronic pneumatic control (EPC), off-the-shelf capillary columns, split/splitless or on-column inlets, standard detectors optimized for capillary columns, and a fast acquisition data system. At any time, users can switch from fast GC back to the original method without major difficulties, or optimize new methods to meet new analytical demands. 

Different sample introduction methods can be used in GC. If the sample is a liquid or a solid dissolved in an appropriate solvent, it may be introduced by a syringe into the injector. The choice of injection system depends on the column type and the sample composition. In packed columns, the sample is injected directly into the column inlet (Figure 2.3). In smaller inner diameter columns, split injection, splitless injection, and on-column injection techniques are used for liquid samples. 

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