Pipetting Techniques

Different pipetting techniques are used in laboratory practice to accurately dispense liquid volumes. Selecting the correct technique is essential for achieving accurate and reproducible experimental results.

Forward pipetting is the standard method for aqueous solutions. The set volume is aspirated and completely dispensed. This technique is suitable for most routine applications and provides accurate results when handling non-problematic liquids.

Reverse pipetting is primarily used for viscous, volatile, or foaming liquids. In this technique, a slightly larger volume is aspirated, leaving a small residual volume in the pipette tip after dispensing. This minimises liquid loss and improves accuracy.

Factors Affecting Pipetting Accuracy

• High or low density: Alters the expansion of the air cushion and thus the dispensed volume.
• Viscosity: Viscous liquids create high flow resistance and may leave residues inside the tip.
• Volatility: Evaporation into the air cushion can cause expansion and droplet formation.
• Foaming liquids: Make accurate aspiration and dispensing more difficult.
• Wetting surfaces: May prevent complete liquid delivery.
• Temperature differences: Affect the air cushion and can lead to measurement errors.

Proper Pipetting Technique

Accurate pipetting requires the selection of the appropriate technique, proper preparation, consistent handling and consideration of physical factors that may affect performance. Following the recommendations below will significantly contribute to obtaining accurate and reproducible results.

Detailed information on pipettes – including types, materials, and applications will be found here.