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Section 17- Troubleshooting
lambda DNA are particularly susceptible to this phenomenon.
Note: Larger volumes used with cuvette-based
spectrophotometers will mask the effect of sample non-
homogeneity.
Perform a Blanking Cycle
This will confirm that the instrument is working well and that any
sample carryover from previous measurements is not a concern.
To run a blanking cycle, perform the following:
1. Open the application software module.
2. Load an aliquot of the blank (the buffer, solvent, or carrier liquid
used with your samples) onto the lower measurement pedestal
and lower the sampling arm into the down position.
3. Click on the ‘Blank’ (F3) button to store the blank reference.
4. Analyze a fresh replicate of the blanking solution as though it
were a sample by selecting ‘Measure’ (F1). The result should
be a spectrum that varies no more than 0.050 A (10mm
absorbance equivalent).
5. Wipe the blank from both measurement pedestal surfaces with
a laboratory wipe and repeat the process until the spectrum is
within 0.005 A (1mm path).
Confirm that reference (blank) solution and solvent are the
same material
Some buffer components absorb in the UV range and therefore it
is critical to blank the instrument with exactly the same material
that the sample is suspended in.
Confirm that your sample is not too dilute
Measuring samples at or near the detection limit will result in
measurements that can vary a significant amount. Refer to the
‘Measurement Concentration Range’ of the application module
that you are using for the applicable measurement range.
Confirm instrument accuracy with CF-1
CF-1 is a concentrated potassium dichromate calibration standard
available from Thermo Fisher Scientific and its distributors. It is a
good practice to check the instrument’s performance every six
months with a fresh vial of CF-1.
260/280 Ratio
Many researchers encounter a consistent 260/280 ratio change when
switching from a standard cuvette spectrophotometer to the
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