A: Infrared Absorption 197F—Use a thin film of melted test specimen.

B: Dissolve or disperse 0.1 g in alcohol, add 10 mL of diluted hydrochloric acid, 5 mL of barium chloride TS, and 10 mL of phosphomolybdic acid solution (1 in 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 10 µg per mL. [note—Prepare the Acetaldehyde 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 50 mL of Polyethylene Glycol 200, and reweigh the flask. Transfer about 5 mL of the liquid ethylene oxide to a 100-mL beaker 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 300 µL (corresponding to about 250 mg) 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 200 to 100.0 g, replace the stopper, and swirl gently to mix. This stock solution contains about 2.5 mg 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 35 mL of Polyethylene Glycol 200, and reweigh the flask. Using a gas-tight gas chromatographic syringe that has been chilled in a refrigerator, transfer about 1 g of the chilled Ethylene oxide stock solution, accurately weighed, to the tared, conical flask. Adjust the weight of the solution with Polyethylene Glycol 200 to 50.0 g, replace the stopper, and swirl gently to mix. Transfer about 10 g of this solution, accurately weighed, to a 50-mL volumetric flask. Add 30 mL of water, and mix. Dilute with water to volume, and mix to obtain a solution containing about 10 µg of ethylene oxide per mL. [note—Prepare this solution fresh just prior to use, and store in a refrigerator.]

Dioxane solution— Dissolve about 1.0 g 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 0.5 mg of dioxane per mL.

Standard solution A— Transfer 0.1 mL of Ethylene oxide solution to a 10-mL pressure headspace vial, add 0.1 mL of Acetaldehyde solution and 0.1 mL of Dioxane solution, seal the vial, and mix.

Standard solution B— Transfer about 1.0 g of the substance under test, accurately weighed, to another 10-mL pressure headspace vial, add 0.1 mL of Ethylene oxide solution, 0.1 mL of Dioxane solution, and 1.0 mL of N,N-dimethylacetamide. Seal the vial, and mix.

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

Chromatographic system (see Chromatography 621)— [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 50 for 5 minutes after injection, then programmed to increase at the rate of 5 per minute to 180, then at the rate of 30 per minute to 230 and then maintained at 230 for 5 minutes. Each vial is heated at a temperature of 90 for 45 minutes before a suitable portion of its headspace is injected. The carrier gas is helium flowing with a linear velocity of about 20 cm per second. [note—If the headspace apparatus is used, then an injection time of 12 seconds and a transfer line temperature of 150 are recommended.] Chromatograph the gaseous phase of Standard solution A, and record the peak responses as directed for Procedure: the relative retention times are about 0.94 for acetaldehyde and 1.0 for 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 1 mL) of the gaseous headspace of Standard solution B and the Test 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 the Test solution are not greater than half the mean areas of the corresponding peaks in the chromatogram obtained from Standard 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 which A is the quantity, in µg, of ethylene oxide added to Standard solution B; rU and rS are the ethylene oxide peak responses obtained from the Test solution and Standard solution B, respectively; and WU and WS are the weights, in g, of the substance under test taken to prepare the Test solution and Standard solution B, respectively: not more than 1 µg per g is found.