Vaporizing Injector

Injection is usually performed with a syringe, through a replaceable, self-sealing plastic or rubber septum into an injector of approximately1 in i.d. (6 mm). The column is attached either to the base of the injector or inserted within it. In the former instance metal fittings are usually used. The injector is heated to facilitate rapid transfer of sample to the column ('flash vaporization'). To limit sample decomposition on hot metal surfaces, the injector usually contains a glass liner that can be replaced when dirty and can be regularly deactivated by silylation. The injector temperature should be high enough to vaporize the components of interest; as the temperature required to do this is rarely known, the temperature is usually set to ca. 50°C above the oven maximum.

The column inserted inside the injector usually reaches almost to the septum and the sample makes contact with the column only ('on-column' injection). Glass columns are installed with fittings incorporating ferrules of graphite or poly(tetrafluoroethylene) (PTFE) and these fittings must be leak-tested regularly. On-column injection can be used equally successfully for small injections of concentrated solutions or larger volumes of dilute solutions - initial band volume (of liquid) is unlikely to exceed 50 |L. For high temperature chromatography the injector is heated and again the volume of vapour is important (unless the injector is heated after injection, when it should be confirmed that the heating rate matches that of the column oven). The injector temperature should not exceed the maximum operating temperature of the stationary phase.

Injectors are rarely heated uniformly; the heating block encloses only part of the injector body and the rest is heated by conduction. Sometimes, to reduce septum decomposition and bleed, the injector is designed so that the septum nut is colder than the rest of the injector. Carrier gas enters the injector through an inlet in the jacket enclosing the injector liner. Usually it is warmed by passage through a coil of stainless-steel tubing wound round the injector heating block; this helps ensure that vaporized sample does not encounter cold carrier gas.

Solar Panel Basics

Solar Panel Basics

Global warming is a huge problem which will significantly affect every country in the world. Many people all over the world are trying to do whatever they can to help combat the effects of global warming. One of the ways that people can fight global warming is to reduce their dependence on non-renewable energy sources like oil and petroleum based products.

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