Standard preparation— [Caution—Ethylene oxide is toxic and flammable.Prepare in a well-ventilated hood,using great care.]Transfer 25mLof dimethylformamide to a 50-mLvolumetric flask,and weigh accurately.Add about 0.5mLof ethylene oxide,and mix.Reweigh to obtain the weight of ethylene oxide by difference.Dilute with dimethylformamide to volume,and mix.Dilute a portion of this solution with dimethylformamide to obtain a Standard preparationhaving a known concentration of about 10ppm of ethylene oxide.

Test preparation— Transfer 1g of Tyloxapol,accurately weighed,to a glass-stoppered,5-mLgraduated cylinder.Dilute with dimethylformamide to 2.0mL,and mix.

Chromatographic system (see Chromatography á621ñ)—The gas chromatograph is equipped with a flame-ionization detector and a 1.8-m ×2-mm glass column containing 5%phase G16on support S12.The injection port is maintained at about 200and the detector at about 250.The column temperature is programmed as follows.The temperature is maintained at 50for 3minutes,then increased to 200at a rate of 25per minute,and held at 200for 5minutes.Helium is used as the carrier gas at a flow rate of about 25mLper minute.Chromatograph the Standard preparation,and record the peak responses as directed for Procedure:the relative standard deviation for replicate injections is not greater than 10%.

Procedure— Separately inject equal volumes (about 3µL)of the Standard preparationand the Test preparationinto the chromatograph,record the chromatograms,and measure the responses for the major peaks.Calculate the quantity,in ppm,of ethylene oxide in the portion of Tyloxapol taken by the formula: in which Cis the concentration,in µg per mL,of ethylene oxide in the Standard preparation,Wis the weight,in g,of Tyloxapol taken in the Test preparation,and rUand rSare the ethylene oxide peak responses obtained from the Test preparationand the Standard preparation,respectively:not more than 10ppm of ethylene oxide are found.

Standard preparations— Weigh 2.7g of formaldehyde solution into a 100-mLvolumetric flask,dilute with water to volume,and mix.Transfer 1.0mLof this solution to a second 100-mLvolumetric flask,dilute with water to volume,and mix.Transfer 10.0mLof this second solution to a third 100-mLvolumetric flask,dilute with water to volume,and mix.Transfer 750µLof this solution to a 25-mLvolumetric flask containing 5mLof a solution of isopropyl alcohol (4in 10).

Test preparation— Transfer 2.0g of Tyloxapol to a 10-mLvolumetric flask,and dissolve in a solution of isopropyl alcohol (4in 10),then dilute with a solution of isopropyl alcohol (4in 10)to volume,and mix.Transfer 500µLof this solution to a 25-mLvolumetric flask containing 5mLof isopropyl alcohol solution (4in 10).

Procedure— To the Standard preparation,the Test preparation,and a blank,prepared by placing 5mLof isopropyl alcohol solution (4in 10)in a 25-mLvolumetric flask,add 500µLof phenylhydrazine hydrochloride solution (7.5in 100),mix,and allow to stand for 10±1minutes.Add 300µLof potassium ferricyanide solution (1in 20)to each flask,mix,and allow to stand for 5minutes ±30seconds.Then add 2.0mLof 2.5Nsodium hydroxide to each,mix,and allow to stand for 4±1minutes.Dilute each flask with isopropyl alcohol solution (4in 10)to volume,mix,and after 10±3minutes determine the absorbances of the preparations,in 1-cm cells,at the wavelength of maximum absorbance at about 520nm,with a suitable spectrophotometer,using the blank to set the instrument.The absorbance of the solution from the Test preparationdoes not exceed that of the solution from the Standard preparation,corresponding to not more than 0.0075%of formaldehyde.