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Recommendations for Pipetting Liquids
Quick links
- Forward, Reverse, Repetitive, & Heterogeneous Sample Pipetting
- 10 Steps to Improve Pipetting Accuracy
- Pipette Accuracy vs. Precision
- Factors Affecting Pipette Accuracy
- Preventing Cross Contamination
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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.
California Proposition 65 Warning: Products manufactured with polycarbonate (PC), polyethylene terephthalate (PET), polyethylene terephthalate glycol (PETG) or polystyrene (PS) contain chemicals known to the State of California to cause cancer, birth defects or other reproductive harm.