Preparation Ratios of Standard Buffer Solutions for pH Meters and pH Electrodes
pH meters and pH electrodes require calibration with standard buffer solutions. When preparing standard buffer substances, the standard buffer mixing ratios must be followed to ensure measurement accuracy. Below is the formulation ratio of standard buffer solutions for calibrating pH meters and pH electrodes:
(1) Potassium trihydrogen oxalate standard buffer solution Accurately weigh 12.61 g of potassium trihydrogen oxalate [KH3(C2O4)2·2H2O] dried at 54±3℃ for 4～5 hours. Dissolve it in water and dilute to 1000 mL.
(2) Potassium hydrogen phthalate standard buffer solution Accurately weigh 10.21 g of potassium hydrogen phthalate [KHC8H4O4] dried at 115±5℃ for 2～3 hours. Dissolve it in water and dilute to 1000 mL.
(3) Phosphate standard buffer solution (pH6.8) Accurately weigh 3.387 g of anhydrous potassium dihydrogen phosphate and 3.533 g of anhydrous disodium hydrogen phosphate, both dried at 115±5℃ for 2～3 hours. Dissolve them in water and dilute to 1000 mL.
(4) Phosphate standard buffer solution (pH7.4) Accurately weigh 1.179 g of anhydrous potassium dihydrogen phosphate and 4.303 g of anhydrous disodium hydrogen phosphate, both dried at 115±5℃ for 2～3 hours. Dissolve them in water and dilute to 1000 mL.
(5) Borax standard buffer solution Accurately weigh 3.80 g of borax [Na2B4O7·10H2O] (Note: avoid weathering). Dissolve it in water and dilute to 1000 mL. Store in a polyethylene bottle with a tight cap to avoid contact with carbon dioxide in air.
