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A:Infrared Absorption á197Fñ— Use a thin film of melted test specimen.

B: Dissolve or disperse 0.1g in alcohol,add 10mLof diluted hydrochloric acid,5mLof barium chloride TS,and 10mLof phosphomolybdic acid solution (1in 10):a precipitate is formed.

Oxyethylene Units per Molecule (Nominal Value)	Hydroxyl Value
2	150–180
10	75–90
20	40–60

Acetaldehyde solution— Prepare a solution of acetaldehyde in water,containing a known concentration of about 10µg per mL.[NOTE—Prepare theAcetaldehyde solution fresh just prior to use.]

Ethylene oxide stock solution— Fill a chilled pressure bottle with liquid ethylene oxide,and store in a freezer when not in use.Use a small piece of polyethylene film to protect the liquid from contact with the rubber gasket.Tare a glass-stoppered conical flask,add about 50mLof Polyethylene Glycol 200,and reweigh the flask.Transfer about 5mLof the liquid ethylene oxide to a 100-mLbeaker chilled in a mixture of sodium chloride and wet ice (1:3).Using a gas-tight syringe that has been previously cooled to –10,transfer about 300µL(corresponding to about 250mg)of liquid ethylene oxide to the Polyethylene Glycol 200,and swirl gently to mix.Replace the stopper,reweigh the flask,and determine the amount of ethylene oxide absorbed by weight difference.Adjust the weight of the mixture with Polyethylene Glycol 200to 100.0g,replace the stopper,and swirl gently to mix.This stock solution contains about 2.5mg of ethylene oxide per g.[NOTE—Prepare this stock solution fresh just prior to use,and store in a refrigerator.]

Ethylene oxide solution— Tare a glass-stoppered conical flask,and chill it in a refrigerator.Add about 35mLof Polyethylene Glycol 200,and reweigh the flask.Using a gas-tight gas chromatographic syringe that has been chilled in a refrigerator,transfer about 1g of the chilledEthylene oxide stock solution,accurately weighed,to the tared,conical flask.Adjust the weight of the solution with Polyethylene Glycol 200to 50.0g,replace the stopper,and swirl gently to mix.Transfer about 10g of this solution,accurately weighed,to a 50-mLvolumetric flask.Add 30mLof water,and mix.Dilute with water to volume,and mix to obtain a solution containing about 10µg of ethylene oxide per mL.[NOTE—Prepare this solution fresh just prior to use,and store in a refrigerator.]

Dioxane solution— Dissolve about 1.0g of dioxane,accurately weighed,in water,and dilute quantitatively,and stepwise if necessary,with water to obtain a solution having a known concentration of about 0.5mg of dioxane per mL.

Standard solution A— Transfer 0.1mLofEthylene oxide solution to a 10-mLpressure headspace vial,add 0.1mLofAcetaldehyde solution and 0.1mLofDioxane solution,seal the vial,and mix.

Standard solution B— Transfer about 1.0g of the substance under test,accurately weighed,to another 10-mLpressure headspace vial,add 0.1mLofEthylene oxide solution,0.1mLofDioxane solution,and 1.0mLof N,N-dimethylacetamide.Seal the vial,and mix.

Test solution— Transfer about 1.0g of the substance under test,accurately weighed,to a 10-mLpressure headspace vial,add 1.0mLof N,N-dimethylacetamide and 0.2mLof water,seal the vial,and mix.

Chromatographic system(see Chromatography á621ñ)— [NOTE—The use of a headspace apparatus that automatically transfers a measured amount of headspace is allowed.]The gas chromatograph is equipped with a flame-ionization detector,maintained at about 250,and a 0.32-mm ×30-m glass or quartz capillary column bonded with a 1.0-µm layer of phase G1.The injection port is equipped with a split injection port with a split ratio of 20:1,and the temperature is maintained at about 150.The column temperature is maintained at 50for 5minutes after injection,then programmed to increase at the rate of 5per minute to 180,then at the rate of 30per minute to 230and then maintained at 230for 5minutes.Each vial is heated at a temperature of 90for 45minutes before a suitable portion of its headspace is injected.The carrier gas is helium flowing with a linear velocity of about 20cm per second.[NOTE—If the headspace apparatus is used,then an injection time of 12seconds and a transfer line temperature of 150are recommended.]Chromatograph the gaseous phase ofStandard solution A,and record the peak responses as directed forProcedure:the relative retention times are about 0.94for acetaldehyde and 1.0for ethylene oxide;the resolution,R,between acetaldehyde and ethylene oxide is not less than 2.0;the dioxane peak is detected with a signal-to-noise ratio of not less than 5;and the relative standard deviation for replicate injections is not more than 15%.

Procedure— Using a heated,gas-tight gas chromatographic syringe,separately inject equal volumes (about 1mL)of the gaseous headspace ofStandard solution Band theTest solution into the chromatograph,record the chromatograms,and measure the areas for the major peaks:the mean areas of the ethylene oxide and dioxane peaks in the chromatogram obtained from theTest solution are not greater than half the mean areas of the corresponding peaks in the chromatogram obtained fromStandard solution B.Calculate the concentration of ethylene oxide,in µg per g,in the portion of the substance under test taken by the formula: in whichAis the quantity,in µg,of ethylene oxide added toStandard solution B;rUandrSare the ethylene oxide peak responses obtained from theTest solution andStandard solution B,respectively;andWUandWSare the weights,in g,of the substance under test taken to prepare theTest solution andStandard solution B,respectively:not more than 1µg per g is found.