Hamilton Microlab STAR - Urp $Vsludwlrq Wr Lvshqvlqj

Microlab
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STAR User Manual
610766/02 Page 13 of 225
• The construction principle enables pressure-based liquid level detection and aspiration
monitoring.
• No contamination or dilution by system liquids.
• No drops due to moving tubes.
• No problems with corroded tubing, pumps, etc.
• Same commonly accepted pipetting principle as for hand pipettes.
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In this section we describe in detail the processes involved in a simple pipetting step.
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The first task for the Microlab STAR is to pick up a disposable tip or a reusable steel needle.
For tips, special carriers typically holding 5 tip racks of 96 tips are placed on the instrument
deck. Steel needles may be picked up directly from the wash station, or from a separate
needle rack, which typically is a tip rack on a tip rack carrier with needles instead of tips.
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The first step within an aspiration and dispense cycle is to aspirate a variable amount of
blowout air, which is used at the end of the (last) dispense, to blow the liquid out of the tip.
This is done with the tips still in the air.
To start the aspiration of liquid, the tip must make contact with the liquid. This may be done
by moving the tip to a IL[HGKHLJKW. This height must be chosen to be permanently below the
liquid level, to prevent the aspiration of air. On aspiration, the tip follows the falling liquid level
(if so specified) according to the volume aspirated. The distance to follow is computed from
the known geometry of the (first segment of the) liquid container.
More elegantly, and with greater safety, the liquid level of the vessel to be aspirated from can
be detected. This can be provided by STAR’s /LTXLG/HYHO'HWHFWLRQ (LLD) feature, based
on either capacitive (cLLD) or pressure (pLLD) signal detection. For conductive liquids,
capacitive LLD should normally be used. The sensitivity of the capacitive LLD that is to be
used depends on the vessel size and the conductivity (or polarity) of the liquid that is to be
detected. For a solution of 0.1% NaCl in distilled water, the sensitivities are:
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1 Very High 384-well plates
2 High 96-well round-bottom plates
3 Medium 96-well flat-bottom plates
4 Low Tubes