Method name: miconazole nitrate - determination of miconazole nitrate - potentiometric titration
Scope of application: This method uses potentiometric titration to determine the content of miconazole nitrate (C18H14Cl4N2O · HNO3).
This method is suitable for the determination of miconazole nitrate.
Method principle: The test sample was precisely weighed, dissolved with glacial acetic acid acetic anhydride (1:1), titrated with perchloric acid titrant according to the potentiometric titration method. The titration result shall be corrected by blank test. Every 1mL of perchloric acid titration solution (0.1mol/L) is equivalent to 47.92mg of C18H14Cl4N2O · HNO3.
Reagent: 1. Water (fresh boiling to room temperature)
2. Glacial acetic acid
3. Acetic anhydride
4. Perchloric acid titrant (0.1mol/L)
5. Reference potassium hydrogen phthalate
6. Water glacial acetic acid
7. Crystal violet indicator
Instrument and equipment:
Sample preparation: 1. Chloric acid titrant (0.1mol/L)
Preparation: Take 750mL of anhydrous glacial acetic acid (5.22mL of acetic anhydride is added for every 1g of water according to the water content), add 8.5mL of perchloric acid (70~72%), shake up, cool down, add an appropriate amount of anhydrous glacial acetic acid to make 1000mL, shake up, and place for 24 hours. If the tested sample is easy to be acetylated, the water content of the solution must be determined by the water measurement method, and then adjusted with water and acetic anhydride to 0.01%~0.2% of the water content of the solution.
Calibration: Take 0.16g of reference potassium hydrogen phthalate dried to constant weight at 105 ℃, weigh it accurately, add 20mL of anhydrous glacial acetic acid to dissolve it, add 1 drop of crystal violet indicator solution, slowly titrate with this solution to blue, and calibrate the titration result with blank test. Every 1mL perchloric acid titrant (0.1mol/L) is equivalent to 20.42mg potassium hydrogen phthalate. Calculate the concentration of the solution according to the consumption of the solution and the amount of potassium hydrogen phthalate.
2. Crystal violet indicator
Take 0.5g of crystal violet and add 100mL of glacial acetic acid to dissolve it.
Storage: put it in a brown glass bottle and keep it tightly.
Operating steps: Take 0.25g of the product, weigh it accurately, add 35mL of glacial acetic acid acetic anhydride (1:1) to dissolve it, titrate it with perchloric acid titrant (0.1mol/L) according to the potentiometric titration method. The titration result shall be corrected by blank test. Every 1mL of perchloric acid titration solution (0.1mol/L) is equivalent to 47.92mg of C18H14Cl4N2O · HNO3.
Note 1: "Precise weighing" means that the weight should be accurate to one thousandth of the weight, and "precise measuring" means that the accuracy of the volume should meet the accuracy requirements of the national standard for the volume pipette.
Note 2: "Moisture determination" uses the drying method. Take 2~5g of the test sample, and lay it flat in a flat weighing bottle that has been dried to constant weight. The thickness does not exceed 5mm, and the loose test sample does not exceed 10mm. Weigh it precisely. Open the bottle cap and dry it at 100~105 ℃ for 5 hours. Cover the bottle cap, move it into a dryer, cool it for 30 minutes, and weigh it precisely. Then dry it at the above temperature for 1 hour, cool it, and weigh it until the difference between two consecutive weighing is not more than 5mg. Calculate the water content (%) of the test article according to the weight loss.