An Autosampler is an instrument which can be used for
different laboratory applications, specifically for Gas Liquid Chromatography.
It is, as the name implies, used to automatically introduce the sample into the
inlets of the apparatus employed in the test. While it is possible to insert
the samples manually into the instrument, it is no more a common practice as
the auto samplers are more efficient and precise method to accomplish results.
Autosamplers can be classified by
their capacity such as auto injectors that are capable of running multiple
samples in one go. Robotic instruments also offer another classification of
these autosamplers with the rotating robots that are being used widely. In the
gas liquid chromatography process, the injector or the column inlet provide the
introduction of the samples as a continuous flow of the carrier gases. Common
inlet types include the split injectors, splitless injectors, on columns
inlets, gas source inlet called as Gas switching valves and PTV injectors. Other systems might include the Solid Phase
micro extractions, Purge and Trap Systems and others. In split and splitless
injector, the sample is introduced using the syringe to heated chamber.
With on column inlet, the sample
is then introduced in its entirety sans the use of heat. The PTV injectors then
introduce the sample at a very controlled temperature through a heater liner.
In the gas source inlet method, the sample is injected into the gas stream
right from the collection bottle, a methods that is used to introduce without
any interruption to the flow of the gas.
The purge and trap autosampler system involves the bubbling
of an inert gas through purging insoluble volatile compound and the aqueous
samples using the matrix. These compounds are later on trapped in an absorbent
column which on heating volatizes to the carrier stream.
The type of the autosampling
system used largely depends on the application. In Gas Chromatography alone,
there are 2 distinct types of columns being used based upon the type of
autosampler being used. There are packaged columns that are usually made up of
stainless steel and glass and contain highly granular, inert and solid material
coated with some solid or liquid stationary phase.
The other type is Capillary Columns. These columns feature a small internal diameter that is being coated
inside with the phase. Other types of capillary columns are made up of semi
solid construction which allows greater flexibility. This allows a long column
be tight wounded into coil which takes up very less room.
While it is usually gas liquid
chromatography that often comes to the mind when are discussing autosampler
types, there are samplers that are being used in different applications from
the geological surveys to life sciences, Pharma industry to water quality
testing and nearly every other application in the materials and life sciences
as well as quality control testing of all types. These instruments have allowed
the labs to handle minute and high samples while increasing efficiency and production.