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Section 14- Cell Cultures
λ
and Abs:
current value of the user-selectable wavelength cursor
and corresponding absorbance. The wavelength can be set by
dragging the cursor, using the up/down arrows or typing in the desired
wavelength.
Baseline:
the absorbance of the user selectable-baseline (horizontal)
cursor. The user may drag this cursor to a new vertical position to
create a new baseline. The absorbance value of the baseline is
subtracted from the absorbance of the spectrum.
Max Absorbance:
used to rescale the upper limit of the vertical axis.
Sample Size Requirements
Field experience has indicated that 1ul samples are sufficient to
ensure accurate and reproducible results when measuring aqueous
samples. However, if you are unsure about your sample composition
or your pipettor accuracy, a 2 ul sample is recommended to ensure
that the liquid sample column is formed and the light path is
completely covered by sample.
Cell Suspension Concentrations
Due to its shorter path length, the NanoDrop 1000 Spectrophotometer
can measure absorbencies that are 10-fold higher than those
measurable on a standard cuvette spectrophotometer. This makes it
possible to directly monitor concentrated cell suspensions. Since the
entire spectrum is displayed, diluted samples exhibiting very low
‘Absorbance’ at 600 nm can be monitored at lower wavelengths, for
example 280 nm.
Sample Homogeneity
The user must be sure to homogeneously suspend the cells when
sampling for “absorbance” measurements and read the sample
immediately to avoid significant cell settling. Vigorous mixing may be
required when measuring concentrated samples.
Decontamination of Measurement Pedestals
If decontamination is necessary, a sanitizing solution, such as a 0.5%
solution of sodium hypochlorite (1:10 dilution of common commercial
bleach solutions – freshly prepared), can be used to ensure that no
biologically active material is present on the measurement pedestals.
The metal fiber optic fittings are made from 303 stainless steel and
are resistant to most common laboratory solvents (see “Solvent
14-2