Pipette assembly comprising a pipette device, a pipette tip, and an expanding mandrel collet coupling device coupling the tip to the pipette device, the coupling device comprising: circumferentially spaced apart segments, an annular base disposed below the segments and comprising a distal portion, an elastomeric element circumscribing the distal portion, and upwardly extending circumferentially spaced apart arms attached at first ends to the annular base and having upper free ends each supporting a different one of the segments configured to expand between a first and a second greater circumference for engaging a first interior working surface of the tip in concurrence with the elastomeric element sealing against a second interior working surface below the first surface and in concurrence with an abutment between a disk exteriorly disposed about a medial portion of the arms and a stepped interior shoulder of the tip disposed between the first and second working surfaces.