8
With pipettes of a nominal volume
≤
50 µl, the error limits are usually smaller than 0.5
µl
. Due to
this small error limit, the evaporation of water during the test procedure has a relatively large influ-
ence on the result. Therefore, the testing of pipettes of this size requires a test procedure which
largely prevents evaporation. To provide a sufficient evaporation protection, special pipette calibration
balances including an evaporation trap can be used.
Pipettes with nominal volume
≤
50 µl
Through the use of calibrated testing devices (balance and thermometer), the requirement of DIN EN
ISO 9001, DIN EN ISO 10012 and DIN EN ISO / IEC 17025 to refer the test to national standards is ful-
filled. The calibration of the balance e.g. can be carried out either by DAkkS calibration or official cert-
ification of the balance, or by calibrating the balance with appropriate weights that are traced to the
national standard. The calibration of the thermometer, hygrometer and barometer can also be carried
out by DAkkS calibration or official certification, or by a comparison with thermometers that are traced
Traceability of test results to national standards
to the national standard (under defined conditions).
5. Calibration - Checking the volume
1. Set the nominal volume at 10% or 20%.
Enter temperature into test record.
►
2. Determine temperature of the test liquid.
3. Place the weighing vessel filled with test liquid on the balance and tare balance.
Note: For multichannel pipettes, each channel has to be tested seperately!
4. Attach new pipette tip. For multichannel pipettes, attach a new pipette tip only to one channel.
Perform conditioning of the pipette. Therefore, aspirate and release test liquid 5 times.
The conditioning increases the accuracy of the test.
►
5. Aspirate test liquid from the recipient vessel. Push the pipetting button to the first stop. Immerse
the pipette tip vertically 2 - 4 mm into the test liquid. For 5 ml and 10 ml pipettes, immerse the
tip 3 - 6 mm. Then release the pipetting button steadily and smoothly.
Observe waiting time: Remain approx. 1 second in the test liquid. For 5 ml and 10 ml pipettes,
►
wait approx. 10 seconds.
6. Release the test liquid into the weighing vessel. Lean pipette tip in an angle of 30° - 45° against the
wall of vessel. Push the pipetting button to the first stop and hold. Push to the second stop to empty
the pipette tip completely. Wipe off pipette tip against the wall of the vessel over a distance of
approx. 10 mm. Then release the pipetting button smoothly.
