Instructions and calibration of pipettes
Laboratory pipette instructions and calibration
The pipettes that are ubiquitous in the laboratory are simple to operate, but perfection is not an easy task.
1. How to choose a suitable range of pipettes?
30%-100% of the maximum volume of the pipette is the optimal range of use. Do not use large-capacity pipettes to pipette small volumes of samples to avoid compromising accuracy.
2. How to choose the appropriate capacity of the tip?
Select a range from 35% to ~100% of the tip's nominal capacity for high-precision pipetting. Said to provide best results when reaching 50% of nominal capacity.
3. Set the pipetting volume
Adjusting from a large range to a small range is the normal adjustment method, just rotate the scale counterclockwise;
When adjusting from a small range to a large range, it should be adjusted to exceed the set volume scale by 1/4 turn, and then back to the set volume, so as to eliminate the mechanical gap and ensure the accuracy of the pipette.
4. Assemble the pipette tip:
Insert the pipette vertically into the tip, rotate it half a turn left and right, and tighten it.
Note: Do not hit the pipette with the pipette. Long-term operation will cause the parts of the pipette to loosen due to the impact. In severe cases, the knob for adjusting the scale will be stuck.
5. Liquid suction and discharge
The tip of the tip is immersed in the liquid surface for 1-6mm, and the depth of the tip immersion is referenced when pipettes with different ranges are aspirating liquid:
In addition, pre-rinsing the pipette tip before aspiration is also very important. Generally, it is recommended to rinse 3 times to ensure the accuracy and accuracy of the pipetting, because a layer of sample will remain on the inner wall of the pipette tip, which will cause errors in the small discharge volume. Rinsing is especially important when pipetting volatile liquids.
Remember the four-character mantra "slow and constant speed" when sucking and discharging fluid, and keep sucking slowly and releasing slowly at a constant speed. Stay for 1-3s after the suction and discharge operation, to prevent the sudden release of the solution from being sucked too fast and rushing into the liquid dispenser to corrode the plunger and cause air leakage; when suctioning liquid, operate vertically. The tip is reliable on the inner wall of the container.
6. After pipetting is completed
After the pipetting operation is completed and the pipette tip is withdrawn, it should be hung on the special gun holder. Students who pursue perfection can adjust the scale to the maximum and let the spring return to the prototype to prolong the service life of the pipette. The pipette with liquid suction should not be placed flat, because the liquid in the pipette tip can easily contaminate the inside of the gun body.
7. How to ensure the accurate amount of liquid when sucking viscous or volatile samples with a manual pipette?
A continuous dispensing pipette with an external plunger is recommended for drawing viscous samples. If you use a built-in piston manual pipette, you can use the reverse pipetting method. When aspirating liquid, press the suction and discharge button to the second stop, and press the button to the first stop when discharging, which can ensure the accuracy of the suction volume.
8. How to check whether there is leakage
After aspirating, stop in the liquid for 1-3 seconds to observe whether the liquid level in the tip drops; if the liquid level drops, first check whether there is any problem with the tip. Confirm that the suction head is OK, there may be a problem with the piston assembly, and you should contact the manufacturer's maintenance personnel.
9. When do I need to recalibrate?
1-2 calibrations per year are recommended depending on the frequency of use.
Pipette pipetting cycle operation steps: 1. Pipette tip installation; 2. Volume setting; 3. Pre-wash pipette tip; 4. Liquid aspiration; 5. Liquid discharge; 6. Remove the pipette tip
