D-2
Appendix D
Pipetting Techniques
Minimizing Cross-Contamination
Cross-contamination of samples is caused by
sample carryover on the probe tip or on its inner
walls. Several methods are available to minimize
cross-contamination.
• Use of the liquid level sensing capability will
reduce carryover by limiting immersion below
the liquid surface.
• Cleansing the probe tip with a flowing rinse
removes contaminants from the external
surfaces of the probe.
• Dispensing liquid through the probe into the
rinsing station will eliminate internal
contamination.
An alternate internal/external cleansing using a
non-flowing rinse is also possible. (Internal rinsing
may not be required at all if large diluent volumes
are dispensed immediately after dispensing of the
sample - a common practice in dilution
procedures.)