Routine Check for pipettes – Best Practices

Quickly check the performance of your pipette

pipette calibration self check

What happens to your pipette’s performance between annual calibrations?

Follow the best practice guidelines below to perform a routine check and learn:

  • What you need to prepare
  • How to perform measurements
  • How to analyze the data

If you wish, you can also download the guidelines as a poster.

Why a routine check?

Pipettes should be calibrated annually to maintain their perfomance. In the interim, it is recommended to perform a routine check to test the functionality of your pipettes in order to be confident with your pipetting results.

Note: On INTEGRA's electronic pipettes you can set a calibration reminder either in days or cycles.

 

1. Environment and materials

thermometer

Environment

Draft free, constant temperature between 15 °C and 30 °C, max. ±0.5 °C deviation during the measurements.

balance

Materials

Balance

Equipped with draft protection and evaporation trap.
Alternative trap: 4 containers filled with water in each corner of the windshield.

Number of required digits is determined by the nominal volume of your pipette:

Volume Digits (Readability)
1 µl ≤ V ≤ 10 µl  6 (0.001 mg)
10 µl < V ≤ 100 µl 5 (0.01 mg)
< 100 µl 4 (0.1 mg)

Weighing container

Preferably use a metal container to minimize build-up of static charges.  
Alternative: 1.5 ml microcentrifuge tube.

Test liquid

Distilled water

pipett tip

Pipette tips

Use pipette manufacturer’s recommended tips for best results.

Note: INTEGRA GripTip pipette tips snap on and never loosen, leak or fall off.

watch and checklist

2. Before you start

Place pipette, tips and test liquid in the test room 2 hours before starting measurements to reach equilibrium with room conditions. 

Note date, ambient temperature and air pressure. If no barometer is available, search the internet for atmospheric pressure at a local weather station.

The use of correct pipetting techniques is crucial.

Pre-wetting and watch

3. Leak test

Before performing any gravimetric measurements, test if the pipette is leaking:

  1. Pre-wet the tip(s) by aspirating and dispensing the nominal volume 3 times
  2. Using the same tip(s), aspirate the nominal volume.
  3. With the tip(s) immersed 2 mm in liquid, hold the pipette vertically for 30 seconds.
  4. If liquid level does not drop, continue with validation. A decreasing liquid level indicates a leak. Contact the manufacturer to discuss further steps.
     
viaflo multichannel pipette with liquid in first and middle channel

4. Gravimetric measurement

The weighing container should not be dry. Add some distilled water.

Number of measurements

Perform at least 4 measurements each at 100 % and at 10 % of the nominal volume. Start at 100 %.

Validate the first and a middle channel on multichannel pipettes.

Procedure

  1. Tare the balance with the weighing container.
  2. Load a new tip.
  3. Perform a pre-wet (see section 3).
  4. Dispense liquid into the weighing container. Ensure to dispense along the inner container wall and finish by drawing the tip end along wall to remove residual liquid. 
  5. Record the weight in a table.
  6. Using the same tip, repeat steps 4 to 5 at least 4 times. Tare the balance after each reading.
  7. Eject the tip and load a new tip.
  8. Repeat steps 1 to 7 for the second test volume.
     

5. Data analysis

  1. Convert balance readings (mg) to volume (µl) using the Z factor (table to determine the correct Z factor):

    pipetting poster formula
    Vi = Single volume in µl
    mi = Single weighing in mg
    Z = Z factor

     
  2. Calculate the mean volume per test volume and per channel:

    pipetting poster formula 2
    V = mean volume
    n = Number of weighings

     
  3. Calculate the accuracy (systematic error) in %:

    pipetting poster formula 3
    es = Systematic error in %
    Vs = Selected test volume
     
  4. Calculate the precision (random error) in %:

    pipetting poster formula 4
    sr = Repeatability standard deviation
    CV = Coefficient of variation in %

     

Compare the calculated accuracy and precision with the manufacturer's specifications. If the calculated values are not within specifications, the pipette needs to be calibrated. If the pipette has passed the routine check, it is working as intended.

Note: INTEGRA electronic pipettes can be easily calibrated. Simply enter target volume and actual volume you have measured and then click calibrate.

Download those guidelines as a poster