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How to calibrate the laboratory pH meter

by:BOQU     2023-04-13
Preheating Turn on the power, press the pH button, the indicator light will be on. In order to stabilize the zero point, it needs to be preheated for more than 30 minutes. 2. Install the electrode Insert the plug of the glass electrode into the socket, and connect the lead wire of the calomel electrode to the binding post. 3. Temperature compensation Turn the temperature compensator to the actual temperature value of the solution to be measured. 4. Zero point adjustment Turn the step switch to '6', turn the zero point adjuster so that the pointer points to '1' in the center of the scale. 5. Calibration Turn the stepping switch to 'Calibration', turn the calibration regulator to make the pointer point to '2.0' on the full scale. 6. Repeat steps (4) and (5) until the displayed value is stable. 7. Positioning When the temperature of the calibration solution is the same as that of the standard buffer solution, check the pH value of the standard buffer solution at this temperature. Add the standard buffer solution into the small beaker, put the stirring bar, immerse the electrode, start the stirrer, turn the step switch to the position corresponding to the known pH value, press the reading switch, and rotate the positioning regulator so that the pointer is stable. The pH value of the standard buffer solution at this temperature. After adjusting, release the reading switch, remove the solution, rinse the electrode, and dry the moisture attached to the electrode with filter paper. 8. Measurement Immerse the electrode in the solution to be tested, press the reading switch, adjust the stepping switch until the indicated value can be read, the indicated value of the stepping switch plus the indicated value of the pointer is the pH value of the tested solution. Hope it can help you! The standard method of pH meter calibration solution configuration in China 1. Introduction: According to the current market application situation, there are three kinds of buffer solutions for pH meter calibration in my country, that is, nominal pH4, pH7 and pH9. , and their respective scientific names are as follows, which the author sorted out based on a number of materials, so that you can quickly and easily understand these problems. Details: 1) pH4: 0.05M potassium hydrogen phthalate solution; 2) pH7: 0.025M Potassium dihydrogen phosphate and disodium hydrogen phosphate mixed salt solution; 3) pH9: 0.01M borax solution; Next, the main configuration and simple methods of the above three solutions are introduced. 2. Standard method for pH meter calibration solution configuration 1) pH4, potassium hydrogen phthalate standard buffer solution: 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 solution (pH7.4): Accurately weigh 4.303g of anhydrous disodium hydrogen phosphate and 1.179g of potassium dihydrogen phosphate, dried at 115±5°C for 2 to 3 hours, add water to dissolve and dilute to 1000ml. Additional supplement: Phosphate standard buffer solution (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 solution: Accurately 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 touch. Summary: 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) Standard solutions can be bought in the market, generally Stored airtight in polyethylene bottles. 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 some liquids or drugs are not allowed to exist during delivery, it can only be provided with dry pH buffers. Customers need to configure them themselves when using them, as long as they are dissolved in 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. 2. Install the electrode Insert the plug of the glass electrode into the socket, and connect the lead wire of the calomel electrode to the binding post. 3. Temperature compensation Turn the temperature compensator to the actual temperature value of the solution to be measured. 4. Zero point adjustment Turn the step switch to '6', turn the zero point adjuster so that the pointer points to '1' in the center of the scale. 5. Calibrate. Point the step switch to 'Calibration', turn the calibration regulator to make the pointer point to the full scale '2.0'. 6. Repeat steps (4) and (5) until the display value is stable. When the temperature of the standard buffer solution is the same as that of the standard buffer solution, check the pH value of the standard buffer solution at this temperature. Add the standard buffer solution into the small beaker, put the stirring bar, immerse the electrode, start the stirrer, turn the step switch to the position corresponding to the known pH value, press the reading switch, and rotate the positioning regulator so that the pointer is stable. The pH value of the standard buffer solution at this temperature. After adjusting, release the reading switch, remove the solution, rinse the electrode, and dry the moisture attached to the electrode with filter paper. 8. Measurement Immerse the electrode in the solution to be tested, press the reading switch, adjust the stepping switch until the indicated value can be read, the indicated value of the stepping switch plus the indicated value of the pointer is the pH value of the tested solution.
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