Patent ID: 8435464

Claim:
A pipetting system comprising: at least one pipetting channel for pipetting of fluids including a channel pump having at least one tip-sided port connected to a pipetting tip by a tip-sided pump conduit which generates a positive or negative pressure in said pipetting tip and at least one reservoir-sided port connected to a system fluid reservoir by a reservoir-sided pump conduit, said channel pump exhibiting a fluid backflow caused by a pressure difference in the tip- and reservoir-sided pump conduits resulting in an effective flow rate (F eff ) compared to a nominal flow rate (F nom ); and a controller which: determines a pressure difference (Δp) between said tip- and reservoir-sided pump conduits; based on said pressure difference (Δp), determines a volume difference (ΔV) between a nominal volume (V nom ) and an effective volume (V eff ) pipetted by operating the channel pump during a pipetting period (T p ) at said nominal flow rate (F nom ), said effective volume (V eff ) being reduced compared to said nominal volume (V nom ) due to said fluid backflow; based on said determined volume difference (ΔV), determines a period extension (ΔT), the period extension (ΔT) being adapted for pipetting of said volume difference (ΔV); and pipettes fluid by operating said channel pump at said nominal flow rate (F nom ) during an extended pipetting period (T tot ) which extends said pipetting period (T p ) by said period extension (ΔT).