Thermo Scientific F1-ClipTip 4641170 Instructions For Use Manual page 10

6.3 Procedure to check calibration
The pipette is checked at maximum volume (nominal volume) and minimum volume. A new tip is
fi rst pre-wetted three to fi ve times and a series of ten pipettings is done at both volumes. A pipette
is always adjusted according to the delivery of the selected volume. Use of the forward pipetting
technique is recommended. The maximum permissible errors are valid for the forward pipetting
method. It is recommended to use the ISO8655 calibration limits in Appendix 3 or user-defi ned
specifi cations.
Procedure:
1. Do 10 pipettings at the minimum volume.
2. Do 10 pipettings at the maximum volume.
3. Calculate the inaccuracy (A) and imprecision (CV) of both series.
4. Compare the results to the limits.
If the calculated results are within the selected limits, the adjustment of the pipette is correct.
Pipette adjustment
Adjustment is done only for one volume. The recommended adjustment volume is the minimum
volume or 10% of the maximum volume.
1. Fit the service tool (Picture 7) into the openings of the
calibration nut at the top of the handle.
2. Turn the service tool clockwise to increase, or
counterclockwise to decrease the volume.
3. After adjustment, check the calibration according to
the instructions above.
Formulas for calculating results
Conversion of mass to volume
V = (w + e) x Z V = volume (μl)
w = weight (mg)
e = evaporation loss (mg)
Z = conversion factor for μl/mg conversion
Evaporation loss can be signifi cant at low volumes. To determine mass loss, dispense water into the
weighing vessel, note the reading and start a stopwatch. Check and note down how much the reading
decreases during 30 seconds (e.g. 6 mg = 0.2 mg/s).
Compare this to the pipetting time from taring to reading. Typically , the pipetting time might be 10
seconds and the mass loss is then 2 mg (10 s x 0.2 mg/s in this example). If an evaporation trap or lid
on the vessel is used, the correction of evaporation is usually unnecessary.
The factor Z is for converting the weight of the water to volume at the test temperature and pressure.
A typical value is 1.0032 μl/mg at 22°C and 95 kPa. See the conversion table in Appendix 1.
Inaccuracy (systematic error)
Inaccuracy is the difference between the dispensed volume and the selected volume of a pipette.
A = V - V A = inaccuracy
0
V = mean volume
V = nominal volume
0
Inaccuracy can be expressed as a relative value: A% = 100% x A / V
Imprecision (random error)
Imprecision refers to the repeatability of the pipettings. It is expressed as standard deviation (S) or
coeffi cient of variation (CV)
Standard deviation can be expressed as a relative value: CV = 100% x S / V
S = standards deviation
V = mean volume
n = number of measurements
10
Picture 7
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