One of the major concerns in any laboratory is data reproducibility and consistency. While user handling and sample variation do play critical roles, pipetting is often neglected space. Quality of the tip, as well as the user practices, can affect the overall results of an experiment. Kosheeka recommends the following tips to improve pipetting accuracy for high-quality data generation. We suggest that these guidelines must be stuck in every work area of the lab as a reminder before every experiment.
Pre-Wetting The Tips
A dry tip increases chances of evaporation of the liquid within the air space of the tip leading to lower volume of the liquid being dispensed. Liquid must be aspirated and dispensed at least thrice before using the tip. This creates humidity which will reduce evaporation of the liquids.
All equipment and liquid must be equilibrated at room temperature before use. Further, handling of the tips must be minimized when not in use as it can transfer body heat and disrupt the temperature equilibrium.
Forward or Reverse Pipetting
While aspirating a liquid, pipette must be depressed till first level and till second level during dispensing.
After aspiration is completely, a small pause must be given before removing tip from the liquid as it continues to flow depending on its viscosity. Viscous liquids will flow up slowly and therefore pipetting must not be hurried between samples.
Angle Of The Pipette
The tip must be held at an angle of 90 degrees to ensure aspiration of complete liquid into the tip. Holding pipette at an angle can lead to inaccuracy in the amount dispensed especially for low volumes of the liquid.
Immersing the pipette tip at a greater depth within a solution will lead to clinging of the sample on the exterior walls of the tip. This will not only compromise the sample quantity but will also generate errors. Similarly, if tip is held just at surface with lesser immersion than required, air bubbles will be trapped thus altering the actual liquid volume aspirated.
You must have wondered why liquid sticks to the walls or the orifice of the tip after delivery of a complete solution. Poor tip quality or tips mismatched for the pipette can generate errors and interfere with sample quality as well. As a practice, only high-quality tips without any defects or rough walls should be used at all times to ensure smooth delivery of the liquid.
When depressing the plunger, accurate and consistent pressure must be applied so that the liquid can be aspirated and dispensed smoothly.
Depending on usage, pipettes must be serviced from a certified supplier at an interval of 6-12 months. This improves their shelf lives and ensures that their usage is smooth.