DEFINITION
Aqueous solution of propane-1,2,3-triol.
Content: 83.5 per cent m/m to 88.5 per cent m/m of propane-1,2,3-triol (C3H8O3; Mr 92.1).
CHARACTERS
Aspect: syrupy liquid, unctuous to the touch, colourless or almost colourless, clear, very hygroscopic.
Solubility: Miscible with water and with ethanol (96 per cent), slightly soluble in acetone, practically insoluble in fatty oils and in essential oils.
IDENTIFICATION
First identification: A, B.
Second identification: A, C, D
A. Refractive index.
B. Infrared absorption spectrophotometry. Comparison Ph. Eur. reference spectrum of glycerol (85 per cent).
C. Mix 1 mL with 0.5 mL of nitric acid. Superimpose 0.5 mL of potassium dichromate solution. A blue ring develops at the interface of the liquids. Within 10 min, the blue colour does not diffuse into the lower layer.
D. Heat 1 mL with 2 g of potassium hydrogen sulfate in an evaporating dish. Vapours (acrolein) are evolved which blacken filter paper impregnated with alkaline potassium tetraiodomercurate solution.
TESTS
Solution S: Dilute 117.6 g to 200.0 mL with carbon dioxide-free water.
Appearance of solution: Solution S is clear. Dilute 10 mL of solution S to 25 mL with water. The solution is colourless.
Acidity or alkalinity: To 50 mL of solution S add 0.5 mL of PhPh solution. The solution is colourless. Not more than 0.2 mL of 0.1 M sodium hydroxide is required to change the colour of the indicator to pink.
Refractive index: 1.449 to 1.455.
Aldehydes: Maximum 10 ppm.
Place 7.5 mL of solution S in a ground-glass-stoppered flask and add 7.5 mL of water and 1.0 mL of decolorised pararosaniline solution. Close the flask and allow to stand for 1 h at a temperature of 25 ± 1C. The absorbance of the solution measured at 552 nm is not greater than that of a standard prepared at the same time and in the same manner using 7.5 mL of formaldehyde standard solution (5 ppm CH2O) Rand 7.5 mL of water. The test is not valid unless the standard is pink.
Esters: Add 10.0 mL of 0.1 M sodium hydroxide to the final solution obtained in the test for acidity or alkalinity. Boil under a reflux condenser for 5 min. Cool. Add 0.5 mL of PhPh solution and titrate with0.1 M hydrochloric acid. Not less than 8.0 mL of 0.1 M hydrochloric acid is required to change the colour of the indicator.
Impurity A and related substances: To pass the test by Gas chromatography.
Limits:
— impurity A: not more than the area of the corresponding peak in the chromatogram obtained with reference solution (c) (0.1 per cent);
— any other impurity with a retention time less than the retention time of glycerol: not more than the area of the peak due to impurity A in the chromatogram obtained with reference solution (c) (0.1 per cent);
— total of all impurities with retention times greater than the retention time of glycerol: not more than 5 times the area of the peak due to impurity A in the chromatogram obtained with reference solution (c) (0.5 per cent);
— disregard limit: 0.05 times the area of the peak due to impurity A in the chromatogram obtained with reference solution (e) (0.05 per cent).
Halogenated compounds: Maximum 30 ppm.
Sugars: To 10 mL of solution S add 1 mL of dilute sulfuric acid and heat on a water-bath for 5 min. Add 3 mL of carbonate-free dilute sodium hydroxide solution (prepared by the method described for carbonate-free1 M sodium hydroxide), mix and add dropwise 1 mL of freshly prepared copper sulfate solution R. The solution is clear and blue. Continue heating on the water-bath for 5 min. The solution remains blue and no precipitate is formed.
Chlorides: Maximum 10 ppm.
Water: 12.0 per cent to 16.0 per cent, determined on 0.200 g.
Sulfated ash: Maximum 0.01 per cent, determined on 5.0 g after heating to boiling and ignition.
ASSAY: Thoroughly mix 0.075 g with 45 mL of water. Add 25.0 mL of a mixture of 1 volume of 0.1 M sulfuric acid and 20 volumes of 0.1 M sodium periodate. Allow to stand protected from light for 15 min. Add 5.0 mL of a 500 g/L solution of ethylene glycol and allow to stand protected from light for 20 min. Using 0.5 mL of PhPh solution as indicator, titrate with 0.1 M sodium hydroxide. Carry out a blank titration.
1 mL of 0.1 M sodium hydroxide is equivalent to 9.21 of C3H8O3.
STORAGE
In an airtight container.
IMPURITIES
A. 2,2′-oxydiethanol (diethylene glycol),
B. ethane-1,2-diol (ethylene glycol),
C. (RS)-propane-1,2-diol (propylene glycol).
C3H8O3 --- 92.10
1,2,3-Propanetriol.
Glycerol --- 56-81-5.
Glycerin contains not less than 99.0 percent and not more than 101.0 percent of C3H8O3, calculated on the anhydrous basis.
Packaging and storage: Preserve in tight containers.
Color: Its color, when viewed downward against a white surface in a 50-mL color-comparison tube, is not darker than the color of a standard made by diluting 0.40 mL of ferric chloride CS with water to 50 mL and similarly viewed in a color-comparison tube of approximately the same diameter and color as that containing the Glycerin.
Identification:
A: Infrared Absorption.
B: Prepare the Test solution and the Resolution solution as directed in the test for Limit of diethylene glycol and related compounds. Dilute a portion of each solution, stepwise if necessary, with water to obtain the Diluted test solution and the Diluted resolution solution having concentrations of about 0.1 mg per mL. Proceed as directed for Procedure in the test for Limit of diethylene glycol and related compounds: the retention time of the glycerin peak in the chromatogram of the Diluted test solution corresponds to that obtained in the chromatogram of the Diluted resolution solution.
Specific gravity: not less than 1.249.
Residue on ignition: Heat 50 g in an open, shallow 100-mL porcelain dish until it ignites, and allow it to burn without further application of heat in a place free from drafts. Cool, moisten the residue with 0.5 mL of sulfuric acid, and ignite to constant weight: the weight of the residue does not exceed 5 mg (0.01%).
Water: not more than 5.0%.
Chloride: A 7.0-g portion shows no more chloride than corresponds to 0.10 mL of 0.020 N hydrochloric acid (0.001%).
Sulfate: A 10-g portion shows no more sulfate than corresponds to 0.20 mL of 0.020 N sulfuric acid (about 0.002%).
Heavy metals: Mix 4.0 g with 2 mL of 0.1 N hydrochloric acid, and dilute with water to 25 mL: the limit is 5 micro-gm per g.
Limit of chlorinated compounds: Accurately weigh 5 g of Glycerin into a dry, round-bottom, 100-mL flask, add 15 mL of morpholine, and connect the flask by a ground joint to a reflux condenser. Reflux gently for 3 hours. Rinse the condenser with 10 mL of water, receiving the washing in the flask, and cautiously acidify with nitric acid. Transfer the solution to a suitable comparison tube, add 0.50 mL of silver nitrate, dilute with water to 50.0 mL, and mix: the turbidity is not greater than that of a blank to which 0.20 mL of 0.020 N hydrochloric acid has been added, the refluxing being omitted (0.003% of Cl).
Fatty acids and esters: Mix 50 g of Glycerin with 50 mL of freshly boiled water and 5 mL of 0.5 N sodium hydroxide, boil the mixture for 5 minutes, cool, add PhPh, and titrate the excess alkali with 0.5 N hydrochloric acid VS. Perform a blank determination: not more than 1 mL of 0.5 N sodium hydroxide is consumed.
Limit of diethylene glycol and related compounds:
Resolution solution: Dissolve accurately weighed quantities of diethylene glycol and USP Glycerin in water, and dilute quantitatively, and stepwise if necessary, with water to obtain a solution having a known concentration of about 0.5 mg of each per mL.
Standard solution: Dissolve an accurately weighed quantity of diethylene glycol in water, and dilute quantitatively, and stepwise if necessary, with water to obtain a solution having a known concentration of about 0.05 mg per mL.
Test solution: Transfer 5 g of Glycerin, accurately weighed, to a 100-mL volumetric flask, dissolve in and dilute with water to volume, and mix.
Chromatographic system: The gas chromatograph is equipped with a flame-ionization detector, a 0.53-mm × 30-m fused-silica analytical column coated with 3.0- micro-m G43 stationary phase, and an inlet liner having an inverted cup or spiral structure. The chromatograph is programmed as follows. Initially, the column temperature is equilibrated at 100 until the time of injection, is increased at a rate of 7.5C per minute to 220C and is maintained at 220C for 4 minutes. The injection port temperature is maintained at 220C, and the detector temperature is maintained at 250C. The carrier gas is helium. The split flow ratio is about 10:1, and the linear flow is maintained at about 38 cm per second. Chromatograph the Resolution solution and record the peak responses as directed for Procedure: the resolution, R, between diethylene glycol and glycerin is not less than 7.0. Chromatograph the Standard solution and record the peak responses as directed for Procedure: the relative standard deviation for replicate injections is not more than 15%.
Procedure: Separately inject equal volumes (about 0.5 microL) of the Standard solution and the Test solution into the chromatograph, record the chromatograms, and measure the responses for all the peaks. Calculate the percentage of diethylene glycol in the portion of Glycerin taken by the formula:
100(CS/CU)(rU/rS)
in which CS is the concentration, in mg per mL, of diethylene glycol in the Standard solution; CU is the concentration, in mg per mL, of Glycerin in the Test solution; and rU and rS are the peak responses for diethylene glycol obtained from the Test solution and the Standard solution, respectively: not more than 0.1% is found. Calculate the percentage of each other impurity, excluding any solvent peaks, in the portion of Glycerin taken by the formula:
100(ri / rs)
in which ri is the peak response of each individual impurity obtained from the Test solution; and rs is the sum of the responses of all the peaks obtained from the Test solution: not more than 0.1% of any individual impurity, excluding diethylene glycol, is found; and not more than 1.0% of total impurities, including diethylene glycol, is found.
1,2,3-Propanetriol
CH2OHCHOHCH2OH --- Formula Weight 92.09
CAS Number 56-81-5
REQUIREMENTS
Assay (by volume): 99.5% C3H5(OH)3
MAXIMUM ALLOWABLE
Color (APHA) 10
Residue after ignition: 0.005%
Neutrality: Passes test
Chlorinated compounds (as Cl): 0.003%
Sulfate (SO4): 0.001%
Acrolein and glucose: Passes test
Fatty acid esters (as butyric acid): 0.05%
Substances darkened by sulfuric acid: Passes test
Heavy metals (as Pb): 2 ppm
Water (H2O): 0.5%.
Glycerol
CH2OHCHOHCH2OH
C3H8O3 --- Formula wt 92.09
INS: 422 CAS: 56-81-5
DESCRIPTION
Glycerin occurs as a clear, colorless, viscous liquid. It is hygroscopic, and its solutions are neutral. Glycerin is miscible with water and with alcohol. It is insoluble in chloroform, in ether, and in fixed and volatile oils.
Function: Humectant; solvent; bodying agent; plasticizer.
REQUIREMENTS
Identification: The infrared absorption spectrum of a thin film of sample exhibits a very strong, broad band at 2.7 micro-m to 3.3 micro-m; a strong doublet at about 3.4 micro-; a maximum at about 6.1 micro-; a strong region of absorption between 6.7 micro-m and 8.3 micro-m, having maxima at about 7.1 micro-m, 7.6 micro-m, and 8.2 micro-m, and a very strong region of bands at about 9.0 micro-m, 9.6 micro-m, 10.1 micro-m, 10.9 micro-m, and 11.8 micro-m.
Note: Glycerin having a low water content may not exhibit a maximum at about 6.1 micro-m.
Assay: Not less than 95.0% and not more than 100.5% of C3H8O3.
Chlorinated Compounds (as Cl): Not more than 0.003%.
Color: Passes test.
Fatty Acids and Esters: Passes test (limit about 0.1%, calculated as butyric acid).
Lead: Not more than 1 mg/kg.
Readily Carbonizable: Substances Passes test.
Residue on Ignition: Not more than 0.01%.
Specific Gravity: Not less than 1.249.
