One of the most crucial factors in enzymatic analysis is volumetric accuracy. Taking care to properly use and maintain micropipettes will save you time, money and frustration in the long run.
It helps to pre-wet new pipette tips by aspirating and dispensing the liquid before pipetting. This forms a thin film on the inner wall of the pipette tip, and guarantees precision across all assays (otherwise the first volume dispensed would be too low).
To pipette, press the pipetting button to the first stop only. Hold the pipette vertically when immersing into the liquid. Avoid using the pipette on a horizontal angle, as liquid may enter and contaminate the shaft. When aspirating, allow the button to slide back slowly to avoid splashing or bubbling, and wait 1-2 seconds before removing.
When you are ready to dispense the sample, press the button slowly to the first stop, pause and then blow out the final volume by pressing the button all the way down to the second stop.
During vintage you should check the condition of micropipettes weekly. Make sure that the shaft is free from contaminants and has not become blocked. Check that the tips fit snuggly, and that the piston seal is secure, by aspirating a sample and holding the pipette vertically for 10 seconds. If liquid drips out of the tip then maintenance may be required. Try to store pipettes in a vertical position (on a rack) rather than lying down.
Check the precision of your pipettes every 3 months. You can simply place a beaker on a lab balance, set the pipette to its maximum volume (or the volume it is mostly used at), and then pipette some distilled water into the beaker (remember to pre-wet the tip!) Record the mass and repeat several times to check repeatability. 1mL of distilled water weighs approximately 1g, however you will need to apply a correction factor for temperature and altitude to convert the mass obtained to a volume.
Under ideal conditions, the maximum error is 3% for most micropipettes in the range of 10µL to 1000µL. If you are concerned that a pipette is not functioning properly, you can follow the calibration procedure available on our website or have it cleaned and calibrated at your nearest Vintessential laboratory.