Pipettes are indispensable precision instruments in the laboratory. Their accurate and reliable operation is crucial to ensure the accuracy and repeatability of experimental results. Correct use can not only improve experimental efficiency, but also effectively avoid errors and contamination caused by improper operation. Therefore, it is important to master the correct usage and precautions of the pipette.
1. Preparation stage 1. Select the optimal measuring range: According to the experimental needs, select the appropriate measuring range. The normal operating volume range of most pipettes is (10-100)% of the indicated range. Although this range is the operable range, performance parameters will change as the volume setting decreases. 2. Tip installation: Insert the pipette vertically into the tip (suction nozzle) and rotate gently to ensure air tightness. Avoid knocking the tip as this may damage the internal parts of the pipette. 3. Capacity setting: Turn the knob of the pipette gun to set the required pipetting volume. Note that the set pipetting volume cannot exceed the specified range of the pipette gun.
2. Pipetting operations 1. Pre-wet the tip: Before taking a new sample, pre-wet the tip with the sample to ensure that the inner wall is evenly moistened and reduce errors. Rinse the tip 2-3 times to form a homogenous film inside the tip, which can improve accuracy by 0.2%. Wetting tips are suitable for solutions with constant temperature. When removing hot and cold solutions, the temperature difference will affect the experimental results. 2. Aspirate liquid: Correct tip immersion depth can improve accuracy by up to 5%, which is especially important for micropipettes. For micropipettes, the tip should be immersed (1-2) mm, while for large-volume pipettes, the immersion depth should be (6-10) mm. 3. Remove the liquid surface: After the suction head is full of liquid, remove the suction head from the liquid surface and wipe off all droplets on the outside of the suction head. 4. Discharge the liquid: Move the suction head to the target container, gently press the operating button to the first stop position, and discharge the liquid. After about 1 second, continue to press the operating button down to the second stop position to blow out the remaining liquid. 5. Release the button: After the liquid is drained, release the button to return it to the starting position.
3. Precautions 1. Keep it vertical: When aspirating, the tip is immersed in the sample at an angle of 90 degrees as much as possible. It is best not to deviate from the vertical position by more than 20 degrees. For pipettes with micro-volumes, pipetting the solution at a vertical angle can improve the performance of pipettes. 2.5% accuracy. Pipetting more than 20° off vertical will result in inaccurate dosing - too much liquid will be sucked in, resulting in inaccurate pipetting. Immersing it at a 60-degree angle will cause your liquid intake to exceed the set 0.7%. 2. Keep stable: Keep stable when pipetting and avoid hand shaking to reduce errors. 3. Avoid holding it for a long time: The pipette should not be held in your hand for a long time to avoid the influence of hand temperature on pipetting accuracy. When not in use, it can be hung on the pipette holder. 4. Regular cleaning and maintenance: After use, the pipette gun should be cleaned in time, especially when corrosive liquids are removed, it should be cleaned thoroughly. It can be cleaned with soapy water or 60% isopropyl alcohol, then rinsed with distilled water and allowed to dry naturally. 5. Avoid impact: Do not hit the pipette tip or other objects with the pipette to avoid damaging the internal gear or affecting accuracy. 6. Calibration: Calibrate the pipette regularly to ensure its accuracy. Calibration can be carried out by repeating the method of weighing distilled water several times in an environment of 20~25℃. 7. Usage record: After using the pipette, remember to fill in the usage record, including date, time, liquid type, etc., for follow-up tracking and auditing.
4. Special pipetting methods 1. Reverse pipetting method: suitable for transferring highly viscous liquids, biologically active liquids, easily foaming liquids or extremely small amounts of liquids. First suck in more liquid than the set range, and do not blow out the remaining liquid when transferring the liquid. The specific operation is: first press the button to the second stop point, slowly release the button to the origin; then press the button to the first stop point to discharge the liquid with the set range; continue to hold the button at the first stop point (otherwise Press down again), remove the tip with residual liquid and discard it. 2. Repeated operation pipetting method: It can be used to quickly and easily transfer the same liquid of the same volume repeatedly. The specific operation is: press the operating button down to the second stop position; immerse the pipette nozzle 2 to 3 mm below the liquid surface, then slowly release the button to suck in the liquid; wait until the pipette nozzle is filled with liquid. Finally, attach the nozzle to the wall of the container to prevent droplets from dripping into the bottle; gently press the operating button to the Discharge the liquid at the first stop position; after the required volume of liquid has been discharged, stop the button at the first stop position (a small amount of liquid not included in the pipetting volume remains in the nozzle); immerse the nozzle Not far below the reagent liquid level, then slowly release the button to allow the nozzle to re-suck the liquid; repeat the above steps.
By mastering and strictly following the correct use of pipettes, we can not only improve the accuracy and reliability of experiments, but also effectively extend the service life of pipettes and reduce maintenance costs. At the same time, this also helps to cultivate a rigorous experimental attitude and good laboratory habits, laying a solid foundation for future scientific research and exploration.
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