Biology is not my domain (rather medicine- particular conditions, diseases), so my answer can only be seen as a linguistic approach.

I might be wrong but I do not think that delivering too much of the liquid by pipette is the point in this particular sentence.
Should that be the case, not a process, but certain negative results (‘adverse effects’) of the process would be the subject of this description.
I think that the German noun describes a process in a meaning ‘transfer fluids/ liquid (using a pipet/pipette). In this respect the meaning is or might be similar to ‘abpipettieren’’ (see the link).

http://de.omegadict.com/Wörterbuch/Deutsch-Englisch/abpipett...

Why do I think so:
In two sources I have found the word-‘over- pippeting’ as a PROBLEM to be solved while using the procedure itself.

Please compare:
[…]
Over-pipetting: Caused by drawing liquid above the cotton filter of a plastic pipette with a PipetAid. Solution: do not draw liquids beyond the recommended hash marks; pay attention to the meniscus when drawing or dispensing liquids.

If liquid has entered a pipette for any reason, report the problem to the pipette supervisor immediately.

And a second extract: ( In link- last entry below –‘ Protect your pipette after etc…)
New ep Dualfilter T.I.P.S® SealMax filter tips from Eppendorf are designed to protect samples and pipettes against contamination through aqueous sample liquid during accidental over pipetting, as well as against contamination through aerosols and biomolecules.
In laboratories where research with precious, potentially harmful, samples is conducted, filter tips are mostly used. Working with adjustable volume pipettes can put the user at risk when combining pipettes with filter tip sizes that are beyond their capacity. An over pipetting situation can cause pipette contamination due to the sample passing through the filter. With the new ep Dualfilter T.I.P.S. SealMax, researchers can be confident their pipette is safe

http://analytica-media.de/prj_275/view/index.cfm?lng=2&nv=6....

DO HTTP

http://de.omegadict.com/Wörterbuch/Deutsch-Englisch/abpipett...

Additional comment – WIKI

A pipette, pipet, pipettor or chemical dropper is a laboratory tool commonly used in chemistry, biology and medicine to transport a measured volume of liquid, ...