Operation Process and Matters Needing Attention of Pipette

The pipette is often used for the pipetting of small or trace liquids in the laboratory, with various specifications, such as single-channel pipette or multi-channel pipette. These two pipettes also have different ranges, such as 0.1-2.5μL, 0.5-10μL, 10-100μL, 20-200μL, 100-1000μL, and so on.

The pipettes with various specifications are designed with different tip sizes.

Although the pipettes’ shapes are slightly different from different manufactures, its working principle and operation don’t change much. The pipette is a precision instrument, so be careful when using and storing it to prevent damage and avoid affecting its range.

Operation process and matters needing attention

Pipetting includes six parts: set the volume value; install the pipette tip; pre-wash the pipette head; aspirate liquid; discharge liquid; withdraw the pipette tip.

1. Set the volume value

Please select a pipette with the correct range before the operation. Operating within 35-100% of the maximum range of the tip can improve the accuracy and repeatability of the operation. The range adjustment can be divided into two steps: first, make a rough adjustment, and quickly adjust the volume to close to the expected value by rotating the button. Then make fine adjustments, place the pipette horizontally, and slowly adjust to the expected value through the adjustment button.

When adjusting from a small range to a large range, rotate continuously in the direction of the required range, and then return to the required range when the rotation reaches 1/3 more than the required range, so as to avoid “mechanical backlash” and ensure higher accuracy. When adjusting from a large range to a small range, it rotates directly and continuously to the required range. At this step, please pay attention to avoid exceeding the maximum or minimum range in the process of adjusting it, so as not to damage the accuracy.

2. Install the pipette tip

Insert the tip, push down the sleeve handle forcefully, and rotate it slightly when necessary. Be careful not to hit the tip with force. This operation will damage the pipette tip and even wear the pipette holster handle, thereby affecting its tightness.

3. Pre-wash the tips

Repeat aspiration and drainage with the same sample two to three times. For micropipettes, this operation helps to absorb the inner wall and can make the air inside the long-range tip equal to the sample temperature, ensuring the consistency of the operation. Please do not rinse with high temperature or low-temperature liquid.

4. Aspirate liquid

Press the discharge button of the pipette to the stop point, and then keep the pipette tip as vertical as possible and immerse it into the liquid surface, keeping the pipette within 20° of the vertical angle. For the immersion depth of the pipette tip, please refer to the recommended depth. If immersed too deeply, too much liquid will be sucked in; on the contrary, if the pipette tip is too close to the surface, air will be sucked in; both operations will cause inaccurate suction volume.

Maintain a constant and consistent pipetting when aspirating, and control the pipetting speed. Rapid or uneven liquid aspiration can cause liquid splashes, resulting in aerosols, contamination of the sleeve, and sample loss. After aspirating the liquid, keep it on the liquid surface for one second, then gently move the pipette tip away, and lightly lean against the wall to remove the liquid stored on the outer wall of the pipette tip.

5. Discharge liquid

When discharging liquid, first confirm that there are no air bubbles in the tip, and the tip lightly leans against the inner wall of the container to discharge the remaining sample, and then slide it up along the inner wall of the container to prevent the liquid from sticking to the mouth of the tip.

6. Withdraw the tip

Press the tip eject button to remove the used tip. Keep it separate from the new tip to avoid cross-contamination. Adjust the pipette back to the maximum range after use.

When using a pipette, you should also pay attention to the effect of temperature on pipetting accuracy. For example, the ideal pipetting temperature is 21.5°C (±1°C). The temperature of the instrument and sample should be the same as the working room temperature and avoid ventilated or sunlit areas that can cause large or sudden temperature changes.

In addition, after a long time of pipetting, the temperature on your hands will heat the pipette, and the air inside the pipette will expand, which will also cause inaccurate results. Therefore, between two pipetting operations, the pipette should be put back into the holder to avoid the influence of hand temperature on pipetting.

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