Quadra 4 Operator Manual
Tomtec
164
1.3 Non Contact Dispensing
The major volume, contained in the tips, is dispensed above the receiving well, by
piston displacement. The final 3-5µL is dispensed with a timed dispense using air
pressure. The tips do not touch the contents of the well. Mixing may also be obtained
with this method of dispensing. The remaining volume to be blown out and the air
pressure used are controlled to be below the splash point.
1.4 Clearing Tip Residual
It is standard pipetting practice to initially aspirate blow out air, to be used to chase
the final residual, in the tip that is retained by capillary action. Using air pressure is far
more effective. A timed dispense is made that provides higher air velocity, to clear
the tip of capillary residual.
2.0 Quadra 450µL Tip Design
The tips for the 450µL head (PN 196-205) are specifically designed with a standard
orifice of 0.036 inches. The tips have a long skinny portion to reach the bottom of a
deep well plate. The upper barrel portion provides the volume. The lower portion
contains 90µL. It may be used for pipeline pipetting. This permits pipetting several
reagents sequentially, using small (10-15µL) air gaps for separation. This combined
with the multiple stations on the Quadra 4 shuttle, means several reagents may be
added in one pass. The larger volume buffer, which is aspirated first, is used to wash
out the smaller volume of drug compound, improving overall precision.
The Quadra tips are retained in their tip rack, allowing them to be loaded and
removed as an integrated individual tips may also be removed for creating pipettor
patterns, since the pipettor head has 96 individual pipettor pistons. Tips may be
removed for 48 well pipetting or 24 well pipetting. With the indexing stage of the
Quadra 4, a single row of tips may be used in the 8 or 12 direction for serial dilution
applications.
2.1 Loading the 450µL Disposable Tips
Tip racks are loaded manually when using the 450µL air displacement pipettor head.
The following describes the tip load protocol on all Quadras using this tip including
the Quadra Plus, Quadra 4, Quadra 3, Quadra 96 Model 320 and the Quadra Tower.
The tips are pressed on to the 96 tip pins by the upward motion of the stage. Each tip
pin has an elastomer “O” ring that seals each disposable tip to the stainless tip pins in
the Quadra head. To keep the tip load force within its design limit, the “O” rings require
periodic lubrication. A pre-lubricated chamois pad, within the tip shuck plate, lubricates
the “O” rings each time the tips are shucked. Periodically, this chamois pad must be re-
lubricated with a technical grade mineral oil.
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