Pipette calibration procedure

Scope of application: Verification of 1 ml, 2 ml, 3 ml, 5 ml, 10 ml, 15 ml, 20 ml, 50 ml, 100 ml single-label straws.
Responsibility: The inspector is responsible for the implementation of this procedure. The director of the inspection office is responsible for the supervision and inspection of the effective implementation of this procedure.
Background knowledge (optional items): None.
Principle (optional item): no calibration procedure:
1. The calibrating principle uses a measure. The weighing method is to weigh the purified water in the Pipette with a balance, and then calculate the volume of the single retort straw according to the density of the pure water at that temperature.
2. Verification project and technical requirements:
2.1 The glass of a single retort straw should be clear and transparent.
2.2 The value of the dividing line and quantity shall be clear, complete and durable. The dividing line shall be straight and evenly divided and must be perpendicular to the axis of the device. The distance between the centers of two adjacent dividing lines shall be greater than 1 mm.
2.3 Single reticle suction pipe should have the following mark:
2.3.1 Factory names and trademarks
2.3.2 Standard Temperature (20°C)
2.3.3 Waiting time t xx S
2.3.4 Usage Marker with "Ex"
2.3.5 nominal total capacity and unit xx ml
2.3.6 Accuracy Level A, B
2.4 Capacity tolerances, water outflow times, and index line widths shall all comply with the following table.

The nominal total nominal capacity of straws (ml) 1 2 3 5 10 15 20 25 50 100
Capacity tolerance (ml) A ±0.007 ±0.010 ±0.015 ±0.020 ±0.025 ±0.030 ±0.05 ±0.08
B ±0.015 ±0.020 ±0.030 ±0.040 ±0.050 ±0.060 ±0.10 ±0.16
Water outflow time (S) A 7~12 15~25 20~30 20~35 25~35 35~45

B 5~12 10~25 15~30 20~35 25~40 30~45
Index line width (mm) ≤ 0.4

3. Verification conditions:
31,000ths of a scale.
3. 2 Temperature range 0 ~ 50 °C, graduated value of 0.1 °C thermometer.
3.3 The stopwatch with 0.1 seconds is used.
3.4 Weighing cups, thermometer tubes, and test frames.
3.5 The room temperature of the calibration laboratory should not exceed 20±5°C and should be stable.
3.6 purified water.
3.7 Single reticle suction tube.
4. Verification method:
4.1 Water Outflow Time:
Purge the purified water with a single-line pipette so that the liquid level reaches about 5mm above the scale mark. Use the index finger to block the pipette tip. Slowly adjust the meniscus to the mark accurately. Release the index finger and time it. Allow the water to fully drain until the liquid level reaches its lowest point. The discharge time shall be in accordance with the requirements in Table 4.2.4.
4.2 Calibration of purified water quality:
Use purified single-line suction pipe to suck purified water so that the liquid level reaches about 5mm above the scale mark. Use the index finger to block the pipette mouth, dry the water on the outer wall of the pipette, and slowly adjust the liquid level to the mark accurately. The weighed cup is placed under a vertical single reticle suction pipe (the measuring cup is tilted by 30 degrees), and the index finger is released so that the purified water flows down the wall of the weighing cup, and when the purified water flows to the tip without flowing, according to the specified time After waiting (15 seconds for class A and 3 seconds for class B), accurately weigh the weight of the weigh cup and water to calculate the quality of purified water.
4.3 Records and Calculations:
4.3.1 Calculation:
V20 = V standard + (P -P)
V20 is the actual capacity (ml) of a single retort straw at a standard temperature of 20°C;
V is marked as the nominal capacity of a single reticle suction (ml);
P is called t °C when the quality of pure water;
P is the quality value of the nominal capacity water at the time of t°C in the measurement method of the "commonly used glass measuring device of the State Metrological Verification Regulations of the People's Republic of China".
When P is said to have a small difference from the P value, the difference in mass can be regarded as a volume difference approximately, so V20=V+AV.
The difference (ΔP) can be found from the measurement method table, because ΔP=V is -P, so V20=P is called +ΔP.
4.3.2 Example:
Use 50ml single-marker pipette (Grade A) to draw distilled water so that the liquid level reaches about 5mm above the scale mark. Use the index finger to block the pipette mouth, wipe off the water on the outer wall of the single-marker pipette, and slowly correct the meniscus. Adjust to the scale, the water temperature is 23.6°C, put the weighed cup under the vertical single reticle suction tube (the measuring cup tilts 30°), release the index finger, and let the purified water flow down the wall of the weighing cup, distilled water Flow to the tip of the flow, waiting for 15s, accurately weighed, calculated to weigh the water in the cup was 49.8560g.
V20=P=+ΔP=49.8560+0.180=50.0360ml
This value meets the A-level standard.
5. Verification process and verification cycle:
Based on the verification data of the above verification items, check the 4.2.4 table to determine whether it meets the corresponding standard level. The verification period is three years, and the single-line pipette used for the alkaline solution is one year.
6. The calibration work is completed and recorded in "Instruments, Meters, Calibration, Verification, Maintenance Records".
Note: Meniscus setting The lowest point of the meniscus should be tangent to the horizontal plane of the edge of the index line. The line of sight should be on the same plane as the index line. Properly arranging the light can make the meniscus dim and clear For this purpose, a white background shall be used to cover off unwanted stray light, and a black paper strip may be placed on the wall of the single reticle suction pipe at a position not more than 1 mm below the positioning surface of the single reticle suction pipe.