In precision laboratory work, pipettes are the core tool for liquid transfer, and their accuracy and reliability are directly related to the accuracy of experimental data and the reliability of scientific research results. However, pipettes often have inaccurate graduations during use, especially after long-term use or improper operation. This problem may not only lead to deviations in experimental results, but may also cause contamination of experimental materials. In serious cases, it may even affect the success or failure of the entire experiment.

1. Possible reasons for inaccurate pipette scales 1. Manufacturing factors: There may be process or material problems during the manufacturing process of the pipette, resulting in inaccurate scales. 2. Wear and aging: Long-term use or improper operation may cause the pipette dial, piston, sealing ring and other parts to wear or age, thus affecting the accuracy of the scale. 3. Temperature changes: The temperature difference between the pipette, the pipette tip and the liquid being pipetted may cause thermal expansion and contraction, thereby affecting the scale reading. 4. Air tightness problem: Poor air tightness between the pipette and the pipette tip may cause liquid leakage, thus affecting the accuracy of the scale. 5. Improper operation: The operator exerts too much force or performs irregular operations when adjusting the scale or pipetting, which may also lead to inaccurate scales.

2. Calibration method for inaccurate pipette scale 1. Calibrate using an electronic balance: (1) Prepare an electronic balance (measuring range 200g, graduation value 0.1mg), beakers (one each for 50mL and 100mL) and several small pieces of qualitative filter paper . (2) Place the electronic balance on a stable workbench and adjust it to a horizontal state. Put a small beaker in and wait until the balance display stabilizes, then press the zero key to return to zero. (3) Adjust the capacity of the pipette to the inspection point (generally choose the minimum, middle and maximum capacity values). (4) Use a pipette to transfer the tested volume of ultrapure water into the small beaker of the balance. After the balance display stabilizes, read and record the value. (5) Repeat the above operation 5 times. After recording is completed, adjust the capacity of the pipette to the next checked point to continue. (6) Based on the recorded data, determine whether the pipette scale is accurate and make necessary adjustments. 2. Use pipette calibration tools: (1) There are special pipette calibration tools on the market that can be used to quickly and accurately calibrate the pipette scale. (2) Follow the instructions of the calibration tool to complete the calibration of the pipette.

3. Preventive measures 1. Choose high-quality pipettes: (1) When purchasing, choose pipettes of well-known brands, reliable quality, and high accuracy to reduce the risk of inaccurate graduations. 2. Standard operation: (1) Operators should be familiar with the use of pipettes and operate in strict accordance with the instructions to avoid damage to the scale caused by excessive force or irregular operation. 3. Regular maintenance: (1) Clean, lubricate and inspect the pipette regularly to ensure that all parts are in good condition. (2) Timely replace worn or aging parts, such as seals, pistons, etc. 4. Pay attention to temperature changes: (1) Before using the pipette, make sure that the temperature of the pipette, tip and liquid being pipetted is the same or similar to reduce the impact of thermal expansion and contraction on the accuracy of the scale. 5. Calibration cycle: (1) Based on the actual conditions of the laboratory and the frequency of use of the pipette, formulate a reasonable calibration cycle and strictly implement it.

Through in-depth analysis of its causes, we realized that manufacturing defects, long-term wear and tear, improper operation and environmental factors may be the "culprits" leading to scale deviation. Faced with this problem, by implementing effective calibration practices, such as using electronic balances or professional calibration tools for accurate calibration, and taking a series of preventive measures, such as selecting high-quality pipettes, standard operations, regular maintenance and calibration, etc., we can Significantly reduces the risk of scale deviation, ensuring pipette accuracy and reliability.

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