pH meter calibration solution preparation
1) pH4, Potassium Hydrogen Phthalate Standard Buffer:
Accurately weigh 10.12g of potassium hydrogen phthalate [KHC8H4O4] dried at 115±5°C for 2 to 3 hours, add water to dissolve and dilute to 1000ml.
2) pH7, phosphate standard buffer (pH7.4):
Accurately weigh 4.303 g of anhydrous disodium hydrogen phosphate and 1.179 g of potassium dihydrogen phosphate, which were dried at 115±5°C for 2 to 3 hours, add water to dissolve and dilute to 1000 ml.
Additional: Phosphate Standard Buffer (pH6.8) Accurately weigh 3.533g of anhydrous disodium hydrogen phosphate and 3.387g of potassium dihydrogen phosphate, dried at 115±5°C for 2 to 3 hours, add water to dissolve and dilute to 1000ml .
3) pH9, borax standard buffer:
Precisely weigh 3.80g of borax [Na2B4O7·10H2O] (note: avoid weathering), add water to dissolve and dilute to 1000ml, put it in a polyethylene plastic bottle, and seal it tightly to avoid contact with carbon dioxide in the air.
Summarize
Judging from the current use of pH meters, there are two types of calibration buffers for domestic pH meters or acidity meters in China:
1) That is, the standard solution is available in the market, and is generally stored in a sealed polyethylene bottle. The standard solution is generally suitable for storage for 1 to 2 months at room temperature. When turbidity, mold or precipitation are found, it cannot be used any longer. Store in a refrigerator at 4°C, and the used standard solution is not allowed to be poured back.
2) You can also buy the buffer yourself and go back to configure it. However, when the general manufacturer delivers the goods, because the country stipulates that some liquids or drugs are not allowed in the delivery, it can only be equipped with a dry PH buffer. When using it, the customer needs to configure it by himself, as long as it is dissolved in a pre-boiled 15 Rinse the remaining reagent in the reagent bag properly in deionized water for ~30 minutes. Then pour it into a 250ml volumetric flask, dilute to the mark, and shake well.
