Recommendations for pipetting liquids

Getting started

  • Check your pipette at the beginning of your working day for dust and dirt on the outside. If needed, wipe with 70 percent ethanol.
  • Check that you are using tips in agreement with the manufacturer's specification. Thermo Scientific pipettes are calibrated using Thermo Scientific pipette tips.
  • To ensure accuracy, use only high-quality tips made from contamination-free virgin polypropylene.
  • Tips are designed for single use. They should not be cleaned for reuse, as their metrological characteristics will no longer be reliable.
  • Pipette parallel samples in a similar way, e.g., pipette in the same position with the tip in the same depth, using the same speed for plunger movements.
  • Avoid turning the pipette on its side when there is liquid in the tip. Liquid might get into the interior of the pipette and contaminate the pipette.
  • Avoid contamination to or from hands by using a tip ejector for tip removal.
  • Always store pipettes in an upright position on a stand when not in use.
Solution and / or compound Examples Pipette Pipette Tip Pipetting technique Comments
Aqueous solution Buffers, diluted salt solutions Air displacement Standard Forward  
Viscous solution Protein and nucleic acid solutions, glycerol, Tween 20/40/60/80 Air displacement

Positive displacement
Standard or wide orifice, Low Retention

Positive displacement
Reverse Pipette slowly to avoid bubble formation.
Volatile compounds Methanol, hexane Air displacement

Positive displacement
Filter/Barrier

Positive displacement
Reverse Pipette rapidly to reduce the effect of evaporation. Carbon filter tips protect the integrity of the pipette by eliminating exposure to harmful vapors.
Body fluids Whole blood, serum Air displacement Standard or wide orifice tip Heterogeneous* Residual liquid can be found on the outer surface of the tip. Wipe the tip against the edge of the vessel to remove this liquid before dispensing.
Nucleotide solutions Genomic DNA, PCR products Air displacement

Positive displacement
Filter/Barrier or wide orifice

Positive displacement
For genomic DNA wide orifice tips can be used to eliminate mechanical shearing.  
Radioactive compounds 14Carbonate,
3H-thymidine
Air displacement

Positive displacement
Filter/Barrier

Positive displacement
Forward  
Acids/alkalis H2SO4, HCI, NaOH Air displacement Filter/Barrier Forward  
Toxic samples   Air displacement

Positive displacement
Filter/Barrier

Positive displacement
Forward or reverse  

*With blood or serum reverse technique is another option. During the aspiration and dispensing, use very slow plunger movements. When aspirating, hold the tips in the liquid for a few seconds, after the plunger is in the upper position. Also, when dispensing, move plunger slowly and wait a few seconds when plunger is in the down position.

Navigate this guide:

Liquid handling
Proper pipetting techniques
Ergonomics
Maintenance & service