Pipettes handle different liquid viscosities depending on their design and the technique used by the operator.
Air Displacement Pipettes: Most pipettes, including both manual and electronic types, operate on the principle of air displacement. In this mechanism, a partial vacuum is created in the pipette tip to draw up the liquid. Liquids with higher viscosity (thicker consistency) may resist flow more than low-viscosity liquids. To accommodate this, operators may adjust their pipetting technique, such as aspirating and dispensing more slowly or using a larger bore tip for viscous liquids.
Positive Displacement Pipettes: These pipettes are specifically designed to handle viscous liquids more effectively. Instead of creating a vacuum to aspirate liquid, positive displacement pipettes use a disposable piston or capillary to physically displace the liquid. This design minimizes the impact of viscosity on pipetting accuracy and precision, making positive displacement pipettes ideal for viscous samples like oils, creams, or gels.
Adjusting Pipetting Technique: For manual pipettes, operators can adjust their technique to compensate for the viscosity of the liquid being pipetted. This may involve adjusting the pipetting speed, angle, or the amount of force applied to the plunger to ensure smooth and accurate dispensing.
Choosing the Right Pipette Tip: Selecting the appropriate pipette tip size can also influence how well a pipette handles viscous liquids. Using a wider bore tip can help reduce resistance and facilitate smoother pipetting of high-viscosity samples.
Electronic
Pipettes: Some electronic pipettes offer specialized modes or settings for pipetting viscous liquids. These may include options for slower aspiration and dispensing rates or adjustable parameters to optimize performance with different viscosity samples.
Pre-wetting: Pre-wetting the pipette tip with a small amount of the liquid being pipetted can help reduce resistance and improve accuracy when pipetting viscous liquids.