5
Test liquid: Water, distilled or deionized, “grade 3” water
conforming ISO 3696. Tests are done in a draft-free room
at a constant (±0.5°C) temperature of water, pipette and
air between 20°C to 25°C. The relative humidity must be
above 55%. Especially with 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.
CHECKING THE CALIBRATION
A new tip is first pre-wetted 3-5 times and a series of ten
pipettings are done with both volumes.
A pipette is always adjusted for delivery (Ex) of the
selected volume. Measuring volumes taken from balance
is not allowed. If the calculated results are in the limits, the
calibration of the pipette is correct.
Procedure:
1. Do 10 pipettings with the lower 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 results are in the limits of Table 1, then the calibration
of the pipette is correct. Otherwise the pipette must be
adjusted and checked again.
Range
Volume
Accuracy
Precision
µl
µl
%
s.d. µl
cv%**
0,5-25 µl 25 µl
±0.625
±2.5
0.250
1.0
5 µl
±0.250
±5.0
0.125
2.5
0.5 µl
*
*
*
*
20-200 µl 200 µl
±3.0
±1.5
0.40
0.2
50 µl
±2.0
±4.0
0.25
0.5
20 µl
*
*
*
*
*User dependent **s.d. = Standard Deviation, CV =
Coefficient of Variation
ADJUSTMENT (Fig.7)
Adjustment is done with the service tool.
1. Place the service tool into the openings of the
calibration nut at the top of the handle.
2. Turn the service tool clockwise to decrease, or
counterclockwise to increase the volume.
3. After adjustment check the calibration according to the
instructions above.
