Poly(ethylene glycol) (Poly(ethylene glycol))

Used in medicine accessories, water-soluble lubricant, macerating agent, unsaturated resin, etc.

Preparation Method of polyethylene oxide: polycondensation of ethylene glycol or polymerization of ethylene oxide with water. Distinguishing test: Solubility: polyethylene glycol with apparent molecular weight of 1000 (or above) is easily soluble in water. Polyethylene glycol is soluble in many organic solvents, including aliphatic ketones and aldehydes, trichloromethane, glycol ethers, esters and aromatic hydrocarbons; Insoluble in ether and most aliphatic hydrocarbons. Solubility in water and organic solvents decreases with the increase of molecular weight. Apparent molecular weight: if the apparent molecular weight is lower than 1000, it is 95.0% ~ 105.0% of the declared value; If the apparent molecular weight is 1000~7000, it is 90.0% ~ 110.0% of the declared value; If it is higher than 7000, 87.5% to 112.5% of the declared value. Quality Index analysis: 1. Acidity (acetometer) take 6g of sample, put it into-250ml Erlenmeyer flask, add several drops of phenolphthalein test solution (TS-167) and 50ml neutral ethanol, and use 0.1mol/L potassium hydroxide ethanol solution to titrate to pink, and maintain 15s. The consumption of drip time shall not exceed 0.5ml. 2. Ethylene oxide is measured according to the following method. (1) preparation of morpholine solution: it is made by mixing one part of heavy distilled morpholine and nine parts of anhydrous methanol. (2) preparation of mixed indicator: take 4,4′-bis-(amino-1-naphthoazo 2,2′-average dibenzenesulfonic acid) 0.050g and bright yellow 0.010g, put it into a 60ml tube bottle. Add 0.1mol/L sodium hydroxide 1.5ml and mix. Add 3.5ml of water and mix. Wash the above mixture in the storage bottle with 45ml methanol, mix it and use it for later use. ??? (3) preparation of standard hydrochloric acid methanol solution: take 8.5ml hydrochloric acid and mix with 1000ml anhydrous methanol. Take 9.00ml of this solution, add several drops of phenolphthalein test solution (TS-167), and use 0.1mol/L sodium hydroxide solution for calibration. Re-calibration is required after 48 hours. ??? (4) operation: take 50ml anhydrous methanol and put it into a-250ml conical flask. Add the above mixed indicator 4~6 drops, and use the above standard hydrochloric acid methanol solution to titrate to pure blue. Add about 25g of sample (accurate weighing) as blank sample liquid, shake until completely dissolved. Use standard hydrochloric acid methanol solution to titrate to pure blue, and add it carefully at the end of titration. (5) take 50ml of morpholine solution, put it into a heat-resistant pressure-resistant bottle, and put the same amount of morpholine solution into a smaller bottle as reagent blank solution. Add about 25g (accurate weighing) of the sample to the first bottle and shake until it is completely dissolved. Close the plug, wrap the bottle firmly and put it into the cloth bag. Put the two bottles next to each other into a water bath at 98℃ ± 2℃. Maintain 30min, the water level in the water bath should be slightly higher than the liquid level in the bottle. After taking it out, let it cool in the air to room temperature. Loosen the wrap, remove the cover to put the residual pressure, and then remove the wrap. Add 20ml of acetic anhydride to each bottle slowly and shake until completely dissolved. Then leave at room temperature for 15min. If the bottle is still hot, it needs to be cooled to room temperature. Add 4~6 drops of indicator to each bottle, and then use the standard methanol hydrochloride solution to titrate to pure blue. When approaching the end point, add a small amount slowly. 3. Determination of ethylene glycol and diethylene glycol: polyethylene glycol sample with apparent molecular weight lower than 450. ??? ① instrument: select an appropriate gas chromatograph, connect a hydrogen flame ionization detector, and use a 15m × 3mm (inner diameter) stainless steel column; 60/80 mesh unpickled diatomaceous earth (Chromosorb W or similar) was used as the carrier, and 12%(weight) Sorbitol was used as the mobile phase. ② basic operating conditions: Column temperature 165℃; Carrier gas is ammonia (or other inert gas) flow rate is 70ml/min; Recorder:-0.5 ~ +1.05mV, full scale response time ls; the hydrogen and air flow during combustion should ensure the maximum sensitivity. ③ preparation of standard solution: accurately weigh the amount of ethylene glycol and diethylene glycol pre-steamed and dissolve in water to prepare chromatographic standard, the concentration of the two standard solutions is 1~6 mg/ml respectively. ? ④ preparation of sample liquid: accurately weigh the sample about 4G, put it into a 10ml volume bottle, and mix it with water for later use. ??? ⑤ operation: Take 2 μl of each of the above two standard solutions, inject chromatographic instrument, and obtain chromatogram respectively. Under standard conditions, the average retention time of ethylene glycol is 2min, and the diethylene glycol is 6.5min. Measure the peak height and record the following values: the peak height of ethylene glycol A,mm; The concentration of ethylene glycol in standard solution B,mg/ml; The peak height of diethylene glycol C,mm; the concentration of diethylene glycol in the standard solution is D,mg/ml.