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Autosamplers are widely used in analytical laboratories to increase sample throughput.
Introduction to Autosamplers. Autosamplers are widely used in analytical laboratories to increase sample throughput, improve injection precision and enable unattended operation – so reducing the labour costs associated with manual injection. All autosamplers have the same basic components which include, the injection valve, a syringe or sampling needle, a loop of either fixed or adjustable volume, a metering pump to aspirate the sample from the vial and an injection port through which the sample is introduced into the loop.
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The Pull to Fill autosampler design draws sample solvent into the injection loop under syringe suction.
A syringe or metering pump device is attached to the sample port of the injector. The needle is inserted into a sample vial and the syringe is drawn back to fill the loop with the desired volume. The syringe drive or pump stepper motor are accurately calibrated to ensure a reproducible volume of sample is withdrawn from the sample vial each time.
During the injection phase the valve configuration allows the mobile phase to flow from the pump directly to the analytical column – effectively by-passing the loop.
The rotation of the valve results in the injection of the contents of the sample loop, which are swept onto the column by the mobile phase flow.
This autosampler design is quite simple, often with a needle that moves in a vertical plane with either a rotating sample tray or articulated arm movement selecting the desired sample vial.
As the main components of the autosampler are not directly flushed by mobile phase during the injection step – it is necessary to flush the sample syringe and needle with a wash solvent between injections in order to reduce carryover. The wash solvent is dispensed to wate. Due to its simplicity and reliability this design was very popular, but is now much less popular due to the other two autosampler designs. See more Autosampler pages here >>