The different operating details of the pipette have different effects on the pipetting accuracy. If all of them are done according to some rough specifications, the efficiency of the operation will inevitably be affected. Therefore, I will classify some relevant usage rules according to their importance: “emphasis†must be observed, but if the accuracy is not high, you do not have to follow “other considerations†and follow the principle of efficiency first. To operate. These two types of considerations are arranged in the order of operation. The following are the key considerations:
Filling the tip
After entering the tip at the lowermost end of the pipette handle, if operating inside the tip box, shake the pipette left or right while gently pressing down or slightly rotate the pipette (only the single pipette can be rotated) ) 1-2 seconds; if using a bulk tip, gently press the tip for 1-2 seconds while gently pressing the tip in the direction of the pipette. If this operation does not achieve the desired seal, the tip and pipette need to be checked (more on this later).
2. Range selection
In general, the available range of pipettes is 10-100% of the maximum range of pipettes. For a particular pipette, the accuracy of pipetting decreases as the amount of pipetting decreases. For example, the REPEARCH pipette of the more common EPPENDORF used in the market, the pipette with a range of 20-200 ul, the accuracy is ±0.6% when removing 200 ul of pure water, when 100 ul of pure water is removed. The accuracy is ±1.0% and the accuracy is ±2.5% when transferring 20ul of pure water (these data are quoted from the product brochure of EPPENDORF). Therefore, the author recommends that the optimal range is 35-100% of the maximum range of the pipette.
3. The speed of aspiration
During the aspiration process, the downward pressure of the thumb must be slowly lowered to allow the liquid to rise evenly and slowly within the tip.
4. Aspiration depth and angle
(1) Depth of tip immersion: There is a table below for reference (of course, the depth required for different containers is slightly different, so there is no need to memorize this form, just grasp two principles: First, the depth of the aspiration should be guaranteed The required amount of pipetting is achieved; second, the outer wall of the tip is exposed to as little liquid as possible).
(2) Angle of pipetting: The pipette must be kept in the vertical state during the pipetting process, and the maximum inclination angle should not exceed 20?.
5. Residence time
For large-scale pipetting (ml class) and pipetting with a viscosity significantly higher than that of the water sample, after releasing the thumb during pipetting, the tip must be allowed to remain in the liquid for 3-5 seconds before being removed (because the liquid enters the tip) The movement is relatively time consuming and must ensure that the liquid achieves a dynamic balance).
6. Storage
After the pipette is used, the pipette must be adjusted to the maximum range and then hung (can be hung on a special stand or attached to the metal crossbar of the test bench).
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