How to use a pipette correctly?

How  to use a pipette correctly?

1. heck the condition of the pipette.
The first thing to do when using a pipette is to check the condition of the pipette. Please refer to the inspection content: whether the scale is in the correct position. If it has not been adjusted to the correct position after use last time, you need to be reminded or even re-calibrated; verify the accuracy of the pipette. If you use the pipette frequently, you will have a rough idea. The position of the liquid level must be carefully observed, and of course the accuracy can be tested; observe whether the pipette is leaking. For old pipettes, be careful that the pipette tips and pipette are not tightly coupled, resulting in dripping problems. ; In addition, try the pipette to feel whether the pipette blows and sucks normally. For example, if the pipette rebounds not smoothly enough, there is a problem; check whether the contact position between the pipette and the pipette tips meets your requirements, especially In the case of microbiological aseptic operations.

Once again, the importance of checking the condition of the pipette is emphasized. Using an inaccurate pipette for experiments will only bring you inaccurate results.

2. Set the capacity value.
Selecting the correct pipette and operating within 35-100% of the tip's maximum capacity can improve operational accuracy and repeatability.

When adjusting the gun, be sure not to exceed the maximum or minimum range to avoid compromising the accuracy of the pipette gun.

To avoid "mechanical backlash", when adjusting from a small range to a large range, rotate continuously in the direction of the required range, rotate to 1/3 turn beyond the required range and then return to the required range. This can avoid "mechanical backlash". ”, ensuring greater accuracy. When adjusting from large range to small range, directly rotate continuously to the required range.

3.  Install the pipette tips.
The correct method is to insert the pipette (device) vertically into the pipette tips, and use a little force to turn it left and right to make it tightly combined. Do not use too much force.

When putting the pipette tips on the pipette, many people will knock the pipette tip box hard several times. This is a wrong approach because it will cause the internal accessories of the pipette(such as springs) to be damaged. The instantaneous impact force generated by knocking may cause the scale adjustment knob to get stuck.

4.  Pre-wash.
Repeat aspiration and dispensing two to three times with the same sample. For micropipettes, this operation facilitates inner wall adsorption and can equalize the air inside the large-capacity tip to the sample temperature, ensuring consistent operation.

Please note that high temperature or low temperature liquids should not be rinsed. Temperature will have an impact on the internal surface area of the tip, affecting the firmness of the tip and the amount of liquid adsorbed by the tip, affecting accuracy.

For organic liquids and highly volatile liquids, their volatilization will form negative pressure in the sleeve, resulting in liquid leakage. Therefore, the number of prewashes must be increased to six times to saturate the gas in the sleeve to avoid liquid leakage.

For viscous liquids, pre-wash should be slow to ensure that the pre-wash reaches the actual position of absorbing the liquid.

5. Aspirate liquid.
When absorbing liquid, just pay attention to the following points: appropriate speed, reduce the amount of liquid on the outer wall of the pipette tips, and whether there is air.

The speed cannot be too fast. If it is too fast, air will be sucked in. If it is too fast, you will have to wait (especially for viscous liquids), or it may lead to inaccurate suction. Sucking too fast can easily cause liquid to enter the inside of the pipette, especially acid. Alkaline substances will damage the pipette.

Reduce the amount of liquid stained on the outer wall of the pipette tip, and the depth of entry into the liquid must be appropriate. Different situations are not the same. Sometimes there is too much liquid stained, and the error can be reduced by combining the pipette and the wall of the vessel. For micro-pipetting operations that require high parallel lines, great attention must be paid to the impact of liquid on the outer wall on the experiment, and the consistency of the operation must be maintained under the premise of standardized operations.

After absorbing liquid, do not tilt the pipette to prevent liquid from entering the inside of the pipette.

6. Discharge.
The core of liquid dispensing is to ensure that all the liquid you draw enters your system, and that the operation is consistent every time. For example, some people say that the tip of the pipette is close to the wall of the container to discharge liquid, which is very undesirable for small volumes to enter large containers. Therefore, there is no fixed method for draining the liquid, and you need to treat it differently according to different situations

7. Retract the pipette tip.
Do not throw the gun tip around to prevent it from entering the sewer.

8.Clean up and return to place.
Check the condition of the pipette against the previous one. After using the pipette, return the pipette to its maximum range, check whether there are any contaminants entering the pipette, clean it in time, and put the pipette in the appropriate position. , to avoid damage.

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