26
General Procedure
7. The pressing motion should be a smooth constant pressure
which is just enough to slide the sample tube inside the
collector tube. A jerky, forced motion may cause added strain to
the tube and could potentially crack it. Press down on the
handle until the stop ring on the sample tube hits the
D end of
the collector tube.
8. Put on the heat-resistant gloves. Push the sample tube and
D
end of each tube all the way into the preheated block so that
the collector tube stop ring touches the block. Placing 21 tubes
should take less than one minute.
9. Set timer for specified time in method.
10. When time is up, put on the heat-resistant gloves. Remove the
first tube from the block and immediately pull off its sample tube
using a downward, twisting motion (Figure 6) as opposed to a
sideways motion. Remove the sample tube within 4 seconds of
removing it from the block or suck-back of the sample will
occur, which may cause low recoveries. Dispose of the sample
tube and the hot solution left in it by dropping it into the sink or
waste bucket.
11. Place each collector tub into the collector tube rack, with the
M
end up (Figure 7). It should take less than two minutes to pull
and separate all 21 tubes. Parafilm the
D end of the tube and
allow the tubes to cool for at least 10 minutes.
Figure 6 Removing the Sample Tube
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