Adjustment - Thermo Scientific Finnpipette Handbuch

volumes under 50 µl the air humidity should be as high as possible to reduce the effect of
evaporation loss. Special accessories, such as the evaporation trap, are recommended.
PROCEDURE TO CHECK CALIBRATION
The pipette is checked with the maximum volume (nominal volume) and with the
minimum volume. A new tip is first pre-wetted 3-5 times and a series of ten pipettings
is done with both volumes. A pipette is always adjusted for delivery (Ex) of the
selected volume.
Procedure:
1. Do 10 pipettings with the minimum volume.
2. Do 10 pipettings with the maximum volume.
3. Calculate the accuracy (A) and precision (cv) of both series.
4. Compare the results to the limits in the Table 1.
If the calculated results are within the selected limits, the adjustment of the pipette is correct.
TABLE 1: Maximum permissible errors according ISO8655
Volume
µl µl
1 ±0.04 ±4.0
2 ±0.05 ±2.5
5 ±0.07 ±1.4
10 ±0.09 ±0.9
20 ±0.12 ±0.6
25 ±0.15 ±0.6
50 ±0.3
100 ±0.4
200 ±0.8
250 ±1.0
500 ±1.5
1000 ±3.0
2000 ±6.0
3000 ±9.0
5000 ±15.0 ±0.3
10 ml ±30.0 ±0.3
Evaporation loss can be significant with low volumes. To determine mass loss,
dispense water to the weighing vessel, note the reading and start a stopwatch. See
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 pipetting time might
be 10 seconds and the mass loss is 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 test temperature and
pressure. A typical value is 1.0032 µl/mg at 22°C and 95 kPa. See the conversion
table on page 36.
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Accuracy Precision
% s.d.* µl cv%
0.04
0.04
0.07
0.08
0.10
0.13
±0.6 0.2
±0.4 0.3
±0.4 0.6
±0.4 0.8
±0.3 1.5
±0.3 0.3
±0.3 4.0
±0.3 6.0
10.0
20.0
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ADJUSTMENT

Adjustment is done with the service tool.
4.0
1. Place the service tool into the openings
2.0
of the calibration nut at the top of the handle.
1.4
2. Turn the service tool clockwise to
0.8
increase, or counterclockwise to
0.5
decrease the volume.
0.5
3. After adjustment check the calibration
0.4
according to the instructions above.
0.3
FORMULAS FOR CALCULATING
0.3
RESULTS
0.3
Conversion of mass to volume
0.3
0.3
V = (w + e) x Z
0.2
V = volume (µl)
0.2
w = weight (mg)
0.2
e = evaporation loss (mg)
0.2
Z = conversion factor for mg/µl conversion
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