Usage: This method uses titration to determine the content of chlorhexidine acetate.
This method is suitable for chlorhexidine acetate.
Method Principle: Dissolve the sample with acetone and glacial acetic acid, add saturated acetone solution of methyl orange, titrate with perchloric acid titration solution, stop titration when the indicator solution of methyl orange turns orange, read out the dosage of perchloric acid titration solution, and calculate the content of chlorhexidine acetate.
Reagent: 1. acetone
2. glacial acetic acid
3. Perchloric acid titration solution (0. 1 mol/L)
4. Methyl orange saturated acetone solution
5. Benchmark potassium hydrogen phthalate
Instruments and equipment:
Sample preparation: 1. Perchloric acid titration solution (0. 1 mole/liter)
Preparation: Take 750 ml anhydrous glacial acetic acid (calculated by water content, add 5.22 ml acetic anhydride per 1g water), add 8.5 ml perchloric acid (70%-72%), shake well, slowly add 23mL acetic anhydride at room temperature, shake while adding, shake well after adding, let cool, and add a proper amount of anhydrous glacial acetic acid to make 65438+. If the test sample is easy to acetylate, the water content of this page must be determined by moisture determination method, and then the water content of this solution should be adjusted to 0.0 1%-0.2% with water and acetic anhydride.
Calibration: Take about 0. 16g of benchmark potassium hydrogen phthalate dried to constant weight at 105℃, accurately weigh it, add 20mL of anhydrous glacial acetic acid to dissolve it, add 1 drop of crystal violet indicator, slowly titrate it to blue with this solution, and correct the titration result with blank test. Every 1mL perchloric acid titration solution (0. 1mol/L) is equivalent to 20.42mg of potassium hydrogen phthalate. According to the consumption of the solution and the amount of potassium hydrogen phthalate, the concentration of the solution can be calculated.
Storage: put it in a brown glass bottle and keep it sealed.
Operating steps: 1. Take about 0.25g of this product, accurately weigh it, add 30mL of acetone and 2mL of glacial acetic acid, shake and dissolve it evenly, add 0.5~ 1mL of saturated acetone solution of methyl orange, titrate with perchloric acid titration solution (0. 1mol/L) until the solution turns orange, and correct the titration result with blank test. Every 1mL perchloric acid titration solution (0. 1mol/L) is equivalent to 3 1.28mg of C22H30Cl2N 10 2C2H4O2.
Note 1: "accurate weighing" means that the weighing should be accurate to one thousandth of the weighed weight, and "accurate weighing" means that the accuracy of measuring the volume should meet the accuracy requirements of the volume pipette in the national standard.
References: China Pharmacopoeia, edited by National Pharmacopoeia Committee, Chemical Industry Press, 20 10, Part II, p.11.