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Section 3-General Operation
“buff” the measurement pedestal surfaces by rubbing each
measurement surface aggressively with a dry laboratory wipe 30-40
times. This will “re-condition” the surface allowing the liquid sample
column to form. Alternatively, use the NanoDrop Pedestal
Reconditioning Compound (PR-1) as a rapid means of reconditioning
the pedestals when the surface properties have been compromised
and liquid columns break during measurement. Additional information
about the PR-1 kit may be found on our website.
Sample Size Requirements
Although sample size is not critical, it is essential that the liquid
column be formed so that the gap between the upper and lower
measurement pedestals is bridged with sample.
Field experience indicates that the following volumes are sufficient to
ensure reproducibility:
•
Aqueous solutions of nucleic acids: 1 ul
•
Purified protein: 2 ul
•
Bradford, BCA or Lowry assay: 2 ul
•
Microbial cell suspensions: 1-2 ul
It is best to use a precision pipettor (0-2 ul) with precision tips to
assure that sufficient sample (1-2 ul) is used. Lower precision
pipettors (0-10 ul and larger) are not as good at delivering 1 ul
volumes to the measurement pedestal. If you are unsure about your
sample characteristics or pipettor accuracy, a 2 ul sample is
recommended.
Sample Carryover
Prevention of sample being retained on the NanoDrop 1000
Spectrophotometer’s measurement pedestals is easily addressed.
Simple wiping of the upper and lower measurement pedestal with a
dry laboratory wipe is highly effective in eliminating carryover for
samples differing in concentration by as much as three orders of
magnitude (see our website for sample data). This is possible since
each measurement pedestal is in actuality a highly polished end of a
fiber optic cable. There are no cracks or crevices for residual sample
to get trapped within.
Sample Homogeneity
Sampling from non-homogeneous solutions – particularly when using
small volumes – can cause significant deviations in the data
generated using all measurement technologies including
3-3