Reverse Pipetting is a technique to improve the accuracy of pipetting liquids that have a higher viscosity than water. Kylt® Reaction Mixes contain glycerin as well as proteins and enzymes. These components make the solution more viscous ("thicker"). To ensure correct transfer of the exact volume of reaction mix needed, we suggest trying the Reverse Pipetting technique.
For standard (forward) pipetting of aequous solutions (water), the user will push the operating button to the first stop and aspirate the liquid. To dispense, the button is again pushed to the first stop and after a short pause, the button is pushed to the second stop to blow out the contents of the pipette tip. This ensures that the complete volume is transferred.
For solutions with higher viscosity, such as Kylt® Reaction Mix and Proteinase K, forward pipetting may lead to a reduced transferred volume, because the liquid attaches to the walls of the pipette tip. In these cases, Reverse Pipetting is often helpful: The user pushes the operating button all the way to the second stop, then aspirates the liquid and dispenses by pushing only to the first stop. Here the additional liquid in the tip replaces the need for a blow out. Dispensing series can be performed by keeping the button at the first stop and the aspirating the next aliquot by slowly releasing the button all the way again. This ensures that no air bubbles are formed and the correct volume is dispensed. At the end the extra volume can be dispensed in the original container.
When pipetting samples, reverse pipetting is helpful, too, to avoid cross-contamination due to forming of bubbles aerosols.
For further reading, plase consider this user guide from Eppendorf.
