Section 5 - Top 10 Tips For Sample Measurement - jenway Genova Nano Operating Manual

SECTION 5 – TOP 10 TIPS FOR SAMPLE MEASUREMENT
1. Ensure the read heads are clean. Wipe both the upper and lower read heads with a lint-free
cloth wetted with deionised water to remove any residues of previous samples. Dry with a fresh
cloth.
2. If a stable droplet does not form, "buff" the read head surfaces by rubbing aggressively with a
dry laboratory wipe 30-40 times. This will "re-condition" the surface.
3. Make sure that the sample is well mixed and free of air bubbles or particles. If a bubble is
created when pipetting the sample, remove the sample and repeat the application.
4. If possible use at least 2µl of sample for measurement. When measuring at 0.2mm path length,
a minimum of 0.5µl can be used.
5. Read each sample droplet only once. The read head moves into a default position after the
sample has been measured. This means that if the sample is measured a second time, contact
of the droplet with the read heads could be lost and the subsequent reading will not give a valid
result.
6. Use a sample of sufficient concentration. Remember that the short path length creates a "virtual
dilution" of the sample of 1 in 20 at 0.5mm and 1 in 50 at 0.2mm. This means that a sample
which would normally read an absorbance of 1.0 in a standard 10mm cuvette will only give a
value of 0.05 at 0.5mm or 0.02 at 0.2mm.
7. To minimise any factors which may interfere with a reading such as sample turbidity or
contaminants carried over from sample preparation, it is recommended that a background
reading is also made at a second reference wavelength (where the absorbance of the sample
is very low and unchanging). In the nucleic acid and protein direct UV modes this option is
defaulted to ON at a wavelength of 320nm; this can be deactivated if required.
8. Use the same measurement mode if comparing the concentrations of samples. Different modes
use different equations to calculate the final sample concentration.
9. Be aware that when measuring micro volume samples, very small changes in absorbance can
lead to much greater differences in calculated concentration values due to the inherent "dilution"
factor of the small path length. For example, when measuring dsDNA, an absorbance change
of just 0.001 equates to a derived concentration change of 1µg/ml at 0.5mm path length (based
on 1 A260 unit of dsDNA = 50µg/ml).
10. Jenway recommends that the micro volume accessory is calibrated every 6 months A set of
calibration solutions (Part code 035 092) are supplied with the Genova Nano
spectrophotometer for this purpose. Full instructions are given in Section 7.
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