A good autosampler is an instrument which is used in a number of different laboratory applications, especially gas-liquid chromatography, where it is used (as the name implies) to automatically expose a sample into the inlets of the apparatus being employed in a given test. Although it is possible to manually insert samples with many instruments, this is no longer the normal practice, since autosamplers offer a more effective and reproducible method.
Autosamplers might be classified by their capacity, such as autosamplers as opposed to auto-injectors; the latter instrument is definitely capable of running more than one sample at the same time. Robotic instruments offer another category of autosampler, with rotating/SCARA robots being among the most widely used.
In gas-liquid chromatography, the column inlet (or injector) provides for the introduction of samples into a continuous flow of carrier gasoline.
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Common inlet types are the split/splitless injectors, on-column inlets, PTV injections, the gas source inlet (also called a gas switching valve), purge and trap systems plus SPME (solid phase micro extraction) systems. In the split/splitless injector, the particular sample is introduced to a heated chamber using a syringe.
With an on-column inlet, the sample is released in its entirety without the use of temperature. PTV injectors introduce the example through a heated liner at a controlled rate. In the gas source inlet method, the sample is inserted into the gas stream from selection bottles, a method which allows samples to become introduced without interrupting the carrier gas flow.
Purge and snare autosampler systems involve bubbling a good inert gas through aqueous samples, purging insoluble volatile compounds through the matrix. These volatile compounds are usually then trapped in an absorbent line which is then heated – the particular volatiles are directed into the transporter stream. Solid phase micro removal (SPME)is a more economical alternative to free and trap systems which provides higher ease of use and a lower cost.
The type of automated sampling system used depends largely on the specific application; in gas chromatography alone, there are two different types of columns used – with the different types of autosampler being more appropriate for one or maybe the other. There are packed columns (usually made of glass or stainless steel and containing an inert, solid and highly granular material which is covered with a liquid or solid stationary phase).
The other type are capillary columns; these columns feature a really small internal diameter, with the inside of the line being coated with the phase. Various other capillary columns are made with a semi-solid construction and parallel micropores; this particular style allows for great flexibility, therefore a long column can be wound in to a tight coil which takes up much less room.
While it is gas and liquid chromatography which often first come to mind when discussing different types of autosampler, you can find samplers used in many different applications from the life sciences to geological research, the pharmaceutical industry, water quality testing and nearly every other software in the materials and life sciences as well as quality control testing of types. These instruments allow laboratories to handle higher sample throughputs whilst increasing reproducibility and efficiency.