Consistent and accurate sampling of semen is a critical step in properly evaluating and processing swine semen. Common errors and inaccuracies while using pipettes can occur from a number of causes, including: improper technique when sampling, dirty or contaminated pipettes and inaccurately calibrated pipettes. The following manufacturer guidelines and recommendations are for maintaining accuracy using air-displacement pipettes when sampling body fluids.
Pipette Use – General Guidelines
- Check your pipette at the beginning of the day for dust and dirt on the outside. If needed, wipe with 70% ethanol.
- Set the volume within the range specified for the pipette.
- Hold the pipette so the ‘grippy finger rest’ rests on your index finger.
- To maximize accuracy, the pipette, tip and semen should be at the same temperature.
- Check that you are using tips recommended for this pipette. To ensure accuracy, use only high-quality tips made from contamination-free polypropylene.
- Tips are designed for single use. They should not be cleaned for reuse as their metrological characteristics will no longer be reliable.
- Pre-rinsing (1-3 times) the tip with the semen may improve accuracy, especially when using positive displacement tips.
- Avoid turning the pipette on its side when there is semen in the tip. Semen might flow into the interior of the pipette and contaminate the pipette.
- Avoid contamination to or from fingers by using the tip ejector and gloves.
- Store pipettes in an upright position when not in use. Pipette stands are ideal for this purpose.
Check the calibration of your pipette regularly, depending on the frequency of use and on the application, but at least twice a year. If used daily, a three-month interval is recommended. Follow the instructions for recalibration in the manufacturer’s instruction manual.
Properly Sampling Semen
The following instructions and diagram demonstrate the proper technique for sampling semen.
- Dip the pipette tip into the semen and press the operating button to the first stop. Make sure the tip is sufficiently below the surface, but not so deep that the pipette barrel is in the semen.
- Slowly release the operating button to the ready position. This action will fill the tip with semen. Do not remove the tip from the solution.
- Press the operating button to the first stop again and release slowly. This action pre-rinses and primes the tip. Repeat this process to load semen into the tip.
- Place the loaded tip into the test tube where the semen is to be diluted.
- Press the operating button to the first stop, then continue pressing to the second stop, which will completely empty the semen from the tip with a puff of air.
- Release the operating button to the ready position.
- Make certain that the pipette tip does not pull in solution from the second stop. This could result in solution coming into the barrel and contaminating the pipette.