How Often A Pipette Calibration Should be Conducted?
The pipette calibration generally needs to be conducted once a year, and if it is used frequently, calibration needs to be more frequent as well
Have you ever wondered whether the pipette you’re using is accurate or not? How do we verify the accuracy of our pipettes? And what should we do if the pipette is not accurate?First, let’s take a look at the errors of different pipettes, as shown in the table below:
The Permissible Error and Measurement Repeatability of The Pipette Capacity
The simplest way to verify the accuracy of a pipette is to use pure water as a sample, weigh it on a balance, and convert the weight to volume to calculate the volume error. As we all know, the density of water varies at different temperatures, so the temperature of the water and the ambient temperature are factors that affect the results when calibrating a pipette.
Another point to note is that different balances must be selected for calibrating different pipettes. The uncertainty of the pipette calibration device (mainly including the balance and thermometer) must meet 1/3 of the maximum allowable error of the pipette. For example, a balance with a calibration interval of 0.1mg cannot be used as a standard device to calibrate a 1μL pipette. After weighing the mass on the balance, the pipette volume at 20°C can be calculated using the following formula:
Pipette Calibration Experiment
The K(t) at different temperatures is shown in the table below:
| Water Tep./℃ | K(t)/(cm2/g) | Water Tep./℃ | K(t)/(cm2/g) | Water Tep./℃ | K(t)/(cm2/g) |
| 15 | 1.004213 | 18.4 | 1.003261 | 21.8 | 1.002436 |
| 15.1 | 1.004183 | 18.5 | 1.003235 | 21.9 | 1.002414 |
| 15.2 | 1.004153 | 18.6 | 1.003209 | 22.0 | 1.002391 |
| 15.3 | 1.004123 | 18.7 | 1.003184 | 22.1 | 1.002369 |
| 15.4 | 1.004094 | 18.8 | 1.003158 | 22.2 | 1.002347 |
| 15.5 | 1.004064 | 18.9 | 1.003132 | 22.2 | 1.002347 |
| 15.6 | 1.004035 | 19.0 | 1.003107 | 22.4 | 1.002303 |
| 15.7 | 1.004006 | 19.1 | 1.003082 | 22.5 | 1.002281 |
| 15.8 | 1.003977 | 19.2 | 1.003056 | 22.6 | 1.002259 |
| 15.9 | 1.003948 | 19.3 | 1.003031 | 22.7 | 1.002238 |
| 16 | 1.003919 | 19.4 | 1.003006 | 22.8 | 1.002216 |
| 16.1 | 1.003890 | 19.5 | 1.002981 | 22.9 | 1.002195 |
| 16.2 | 1.003862 | 19.6 | 1.002956 | 23.0 | 1.002173 |
| 16.3 | 1.003833 | 19.7 | 1.002931 | 23.1 | 1.002152 |
| 16.4 | 1.003805 | 19.8 | 1.002907 | 23.2 | 1.002131 |
| 16.5 | 1.003777 | 19.9 | 1.002882 | 23.3 | 1.002110 |
| 16.7 | 1.003721 | 20.0 | 1.002858 | 23.4 | 1.002089 |
| 16.8 | 1.003693 | 20.1 | 1.002834 | 23.5 | 1.002068 |
| 16.9 | 1.003665 | 20.2 | 1.002809 | 23.6 | 1.002047 |
| 17 | 1.003637 | 20.3 | 1.002785 | 23.7 | 1.002026 |
| 17.1 | 1.003610 | 20.4 | 1.002761 | 23.8 | 1.002006 |
| 17.2 | 1.003582 | 20.5 | 1.002737 | 23.9 | 1.001985 |
| 17.2 | 1.003582 | 20.6 | 1.002714 | 24.0 | 1.001965 |
| 17.3 | 1.003555 | 20.7 | 1.002690 | 24.1 | 1.001945 |
| 17.4 | 1.003528 | 20.8 | 1.002666 | 24.2 | 1.001924 |
| 17.5 | 1.003501 | 20.9 | 1.002643 | 24.3 | 1.001904 |
| 17.6 | 1.003474 | 21.0 | 1.002619 | 24.4 | 1.001884 |
| 17.7 | 1.003447 | 21.1 | 1.002596 | 24.5 | 1.001864 |
| 17.8 | 1.003420 | 21.2 | 1.002573 | 24.6 | 1.001845 |
| 17.9 | 1.003393 | 21.3 | 1.002550 | 24.7 | 1.001825 |
| 18 | 1.003367 | 21.4 | 1.002527 | 24.8 | 1.001805 |
| 18.1 | 1.003340 | 21.5 | 1.002481 | 24.9 | 1.001786 |
| 18.2 | 1.003314 | 21.6 | 1.002459 | 25.0 | 1.001766 |
| 18.3 | 1.003288 | 21.7 | 1.002459 | / | / |
Another common method is located at this position
With the specialized standard wrench, adjustments can be made. The most convenient option is the electronic pipette, which directly enters the calibration interface, allowing input of calibration results for self-calibration.For non-digital pipettes, the entire calibration process requires patience, with adjustments repeated until the data meets the maximum allowable error requirements.Considerations include:Throughout the calibration process, room temperature should be maintained at (20±5)°C, with temperature fluctuations not exceeding 1°C/h.Distilled water or deionized water should be used, with a temperature difference of ≤2°C between the water and the environment.The pipette should be left in the calibration environment for 4 hours before starting the calibration process
