1. Identification method of hydroxypropyl methylcellulose
(1) Take 1.0g of sample, heat 100mL of water (80~90℃), stir continuously, and cool in an ice bath until it becomes a viscous liquid; put 2mL of the liquid into a test tube, and slowly add 1mL of 0.035% anthrone sulfuric acid along the tube wall solution and leave it for 5 minutes. A green ring appears at the interface between the two liquids.
(2) Take an appropriate amount of the mucus used for identification in (I) above and pour it on the glass plate. As the water evaporates, a ductile film forms.
2. Preparation of hydroxypropyl methylcellulose analysis standard solution
(1) Sodium thiosulfate standard solution (0.1mol/L, validity period: 1 month)
Preparation: Boil about 1500mL distilled water, cool and set aside. Weigh 25g sodium thiosulfate (its molecular weight is 248.17, try to be as accurate as about 24.817g when weighing) or 16g anhydrous sodium thiosulfate, dissolve it in 200mL of the above cooling water, dilute to 1L, place it in a brown bottle, and place Store in a dark place, filter and set aside after two weeks.
Calibration: Weigh 0.15g of reference potassium dichromate and bake to constant weight, accurate to 0.0002g. Add 2g potassium iodide and 20mL sulfuric acid (1+9), shake well, and place in the dark for 10 minutes. Add 150mL water and 3ml 0.5% starch indicator solution, and titrate with 0.1mol/L sodium thiosulfate solution. The solution changes from blue to blue. Turns bright green at the end point. No potassium chromate was added in the blank experiment. The calibration process is repeated 2 to 3 times and the average value is taken.
The molar concentration C (mol/L) of sodium thiosulfate standard solution is calculated according to the following formula:
In the formula, M is the mass of potassium dichromate; V1 is the volume of sodium thiosulfate consumed, mL; V2 is the volume of sodium thiosulfate consumed in the blank experiment, mL; 49.03 is the dichromium equivalent to 1 mol of sodium thiosulfate. Mass of potassium acid, g.
After calibration, add a small amount of Na2CO3 to prevent microbial decomposition.
(2) NaOH standard solution (0.1mol/L, validity period: 1 month)
Preparation: Weigh about 4.0g of pure NaOH for analysis into a beaker, add 100mL of distilled water to dissolve, then transfer to a 1L volumetric flask, add distilled water to the mark, and leave it for 7-10 days until calibration.
Calibration: Place 0.6~0.8g of pure potassium hydrogen phthalate (accurate to 0.0001g) dried at 120°C into a 250mL Erlenmeyer flask, add 75mL of distilled water to dissolve, and then add 2~3 drops of 1% phenolphthalein indicator. Titrate with titrant. Stir the sodium hydroxide solution prepared above until it is slightly red, and the color does not fade within 30 seconds as the end point. Write the volume of sodium hydroxide. The calibration process is repeated 2 to 3 times and the average value is taken. And do a blank experiment.
The concentration of sodium hydroxide solution is calculated as follows:
In the formula, C is the concentration of sodium hydroxide solution, mol/L; M represents the mass of potassium hydrogen phthalate, G; V1 – the volume of sodium hydroxide consumed, mL; V2 represents the sodium hydroxide consumed in the blank experiment Volume, mL; 204.2 is the molar mass of potassium hydrogen phthalate, g/mol.
(3) Dilute sulfuric acid (1+9) (validity period: 1 month)
While stirring, carefully add 100 mL of concentrated sulfuric acid to 900 mL of distilled water and add slowly while stirring.
(4) Dilute sulfuric acid (1+16.5) (validity period: 2 months)
While stirring, carefully add 100 mL of concentrated sulfuric acid to 1650 mL of distilled water and add slowly. Stir as you go.
(5) Starch indicator (1%, validity period: 30 days)
Weigh 1.0g of soluble starch, add 10mL of water, stir and pour into 100mL of boiling water, boil for 2 minutes, let stand, and take the supernatant for later use.
(6) Starch indicator
Take 5 mL of the prepared 1% starch indicator solution and dilute it with water to 10 mL to obtain 0.5% starch indicator.
(7) 30% chromium trioxide solution (validity period: 1 month)
Weigh 60g of chromium trioxide and dissolve it in 140mL of organic-free water.
(8) Potassium acetate solution (100g/L, valid for 2 months)
Dissolve 10 g of anhydrous potassium acetate granules in 100 mL of a solution of 90 mL of glacial acetic acid and 10 mL of acetic anhydride.
(9) 25% sodium acetate solution (220g/L, validity period: 2 months)
Dissolve 220g anhydrous sodium acetate in water and dilute to 1000mL.
(10) Hydrochloric acid (1:1, validity period: 2 months)
Mix concentrated hydrochloric acid and water in a 1:1 volume ratio.
(11) Acetate buffer (pH=3.5, validity period: 2 months)
Dissolve 60mL of acetic acid in 500mL of water, then add 100mL of ammonium hydroxide and dilute to 1000mL.
(12) Lead nitrate preparation solution
Dissolve 159.8 mg lead nitrate in 100 mL water containing 1 mL nitric acid (density 1.42 g/cm3), dilute to 1000 mL water, and mix well. Well fixed. The solution should be prepared and stored in lead-free glass.
(13) Lead standard solution (validity period: 2 months)
Accurately measure 10mL of lead nitrate preparation solution and add water to dilute to 100mL.
(14) 2% hydroxylamine hydrochloride solution (validity period: 1 month)
Dissolve 2g of hydroxylamine hydrochloride in 98mL of water.
(15) Ammonia (5mol/L, valid for 2 months)
Dissolve 175.25g ammonia water and dilute to 1000mL.
(16) Mixed liquid (validity: 2 months)
Mix 100mL of glycerol, 75mL of NaOH solution (1mol/L) and 25mL of water.
(17) Thioacetamide solution (4%, valid for 2 months)
Dissolve 4g of thioacetamide in 96g of water.
(18) Phenanthroline (0.1%, validity period: 1 month)
Dissolve 0.1g of phenanthroline in 100mL of water.
(19) Acidic stannous chloride (validity period: 1 month)
Dissolve 20g of stannous chloride in 50mL of concentrated hydrochloric acid.
(20) Potassium hydrogen phthalate standard buffer solution (pH 4.0, validity period: 2 months)
Accurately weigh 10.12g of potassium hydrogen phthalate (KHC8H4O4) and dry it at (115±5)℃ for 2 to 3 hours. Dilute to 1000mL with water.
(21) Phosphate standard buffer solution (pH 6.8, validity period: 2 months)
Accurately weigh 3.533g anhydrous disodium hydrogen phosphate and 3.387g potassium dihydrogen phosphate dried at (115±5)°C for 2~3 hours, and dilute to 1000mL with water.
3. Determination of hydroxypropylmethylcellulose group content
(1) Determination of methoxyl content
The determination of the methoxy group content is based on the test containing methoxy groups. Hydroiodic acid decomposes upon heating to produce volatile methyl iodide (boiling point 42.5°C). Methyl iodide was distilled with nitrogen in the self-reactive solution. After washing to remove interfering substances (HI, I2 and H2S), methyl iodide vapor is absorbed by the acetic acid solution of potassium acetate containing Br2 to form IBr, which is then oxidized to iodic acid. After distillation, the contents of the receptor are transferred to an iodine bottle and diluted with water. After adding formic acid to remove excess Br2, KI and H2SO4 are added. The methoxyl content can be calculated by titrating 12 with Na2S2O3 solution. The reaction equation can be expressed as follows.
The methoxyl content measuring device is shown in Figure 7-6.
In 7-6(a), A is a 50mL round-bottomed flask connected to a catheter. There is a straight air condensation tube E vertically installed at the bottleneck, about 25cm long and 9mm inner diameter. The upper end of the tube is bent into a glass capillary tube with an inner diameter of 2 mm and an outlet facing downward. Figure 7-6(b) shows the improved device. Figure 1 shows the reaction flask, which is a 50mL round-bottomed flask, with a nitrogen tube on the left. 2 is the vertical condenser tube; 3 is the scrubber, containing washing liquid; 4 is the absorption tube. The biggest difference between this device and the Pharmacopoeia method is that the two absorbers of the Pharmacopoeia method are combined into one, which can reduce the loss of the final absorption liquid. In addition, the washing liquid in the scrubber is also different from the pharmacopoeia method. It is distilled water, while the improved device is a mixture of cadmium sulfate solution and sodium thiosulfate solution, which is easier to absorb impurities in the distilled gas.
Instrument pipette: 5mL (5 pieces), 10mL (1 piece); Burette: 50mL; Iodine volume bottle: 250mL; Analytical balance.
Reagent phenol (because it is a solid, it will melt before feeding); carbon dioxide or nitrogen; hydroiodic acid (45%); analytical grade; potassium acetate solution (100g/L); bromine: analytical grade; formic acid: analytical grade; 25% Sodium acetate solution (220g/L); KI: analytical grade; dilute sulfuric acid (1+9); sodium thiosulfate standard solution (0.1mol/L); phenolphthalein indicator; 1% ethanol solution; starch indicator: 0.5% Starch aqueous solution; dilute sulfuric acid (1+16.5); 30% chromium trioxide solution; organic-free water: add 10mL of dilute sulfuric acid (1+16.5) to 100mL of water, heat to boiling, and add 0.1ml of 0.02mol/L permanganic acid Potassium titer, boil for 10 minutes, must remain pink; 0.02mol/L sodium hydroxide titrant: Calibrate the 0.1mol/L sodium hydroxide titrant according to the Chinese Pharmacopoeia Appendix method, and accurately dilute to 0.02mol with boiled and cooled distilled water /L.
Add about 10mL of washing liquid into the washing tube, add 31mL of newly prepared absorption liquid into the absorption tube, install the instrument, weigh about 0.05g of the dried sample that has been dried to constant weight at 105°C (accurate to 0.0001g), add the reaction at ℃ In the bottle, add 5 mL of hydroiodide. Quickly connect the reaction bottle to the recovery condenser (moisten the grinding port with hydriodic acid), and pump nitrogen into the tank at a rate of 1 to 2 bubbles per second.