7.8. Calibration Check (Mode d1, 1:5, 5 mL dilution)
Genuine 3M Electronic Pipettor Tips are strongly recommended for verifying pipettor performance. Perform a single-sample measurement following
a change of any removable parts. Perform a 4-sample test monthly-or more frequently, depending on use. Perform a 10-sample test quarterly.
Record all results and maintain records. Use the procedure indicated by the American Public health Association (APhA) "Standard Methods for the
Examination of Dairy Products".
1. Allow the pipettor, pipettor tips and test liquid to adjust to room temperature
(19°-25°C/66°-77°F) for one day before beginning the calibration check.
2. note the temperature before starting the check. You will need this to compare your result to the calibration check chart.
3. Double-rinse the pipettor tip by aspirating water to the 5.0 mL level (4.0 mL+1.0 mL) and then expelling it.
4. Place a 50 mL or smaller vessel containing 20-25 g of distilled water onto an analytical balance. Note its weight. Re-tare balance to 0 (zero).
5. Aspirate 4.0 mL of water from the vessel on the analytical balance. Note its weight. Re-tare balance to 0.
6. Aspirate an additional 1.0 mL from the vessel on the analytical balance. Note its weight. Re-tare balance to 0.
7. Expel the 5.0 mL of water back into the vessel on the analytical balance. Note its weight. Re-tare balance to 0.
8. Repeat steps 4-6, as desired.
9. Calculate the average weight of the 4.0 mL aspirations. Repeat this calculation for the 1.0 mL and 5.0 mL measurements.
10. Refer to Table 1, below. Find the temperature closest to the temperature you recorded during step 1. Confirm that each average weight falls within
corresponding weight tolerance range for that temperature.
Table 1
Calibration Check Chart
1:5 Dilution Test Volume>
Volume (mL) Tolerance Range>
Temperature
19°C
20°C
21°C
22°C
23°C
24°C
25°C
26°C
27°C
28°C
29°C
30°C
*Weights adjusted for temperature and pressure effects using the "z-factor".
4.00 mL
3.968-4.032 mL
Weight (g) Tolerance Range*
3.9585-4.0207 g
3.9577-4.0199 g
3.9569-4.0191 g
3.9557-4.0179 g
3.9549-4.0171 g
3.9542-4.0163 g
3.9530-4.0151 g
3.9522-4.0139 g
3.9510-4.0131 g
3.9498-4.0119 g
3.9487-4.0107 g
3.9475-4.0099 g
21
1.00 mL
0.979-1.021 mL
Weight (g) Tolerance Range*
0.9767-1.0181 g
0.9765-1.0179 g
0.9763-1.0177 g
0.9760-1.0174 g
0.9758-1.0172 g
0.9756-1.0170 g
0.9753-1.0167 g
0.9751-1.0164 g
0.9748-1.0162 g
0.9745-1.0159 g
0.9742-1.0156 g
0.9739-1.0154 g
(English)
5.00 mL
4.945-5.055 mL
Weight (g) Tolerance Range*
4.9332-5.0409 g
4.9322-5.0399 g
4.9312-5.0389 g
4.9297-5.0374 g
4.9287-5.0364 g
4.9278-5.0354 g
4.9263-5.0339 g
4.9253-5.0324 g
4.9238-5.0314 g
4.9224-5.0299 g
4.9209-5.0283 g
4.9194-5.0273 g