Phenol solution,Standard solution,Test solution,and Chromatographic system— Prepare as directed under Chromatographic purity.

Procedure— Separately inject equal volumes (about 1µL)of the Standard solutionand the Test solution into the chromatograph,record the chromatograms,and measure the peak area responses.Calculate the percentage of phenol in the portion of Phenoxyethanol taken by the formula: in which Cis the concentration,in mg per mL,of phenol in the Standard solution;Wis the weight of Phenoxyethanol,in mg,taken to prepare the Test solution;and rUand rSare the peak areas of the phenol peak in the chromatograms obtained from the Test solutionand the Standard solution,respectively:not more than 0.1%is found.

Phenol solution— Prepare a solution of phenol in isopropyl alcohol having a known concentration of about 0.25mg of phenol per mL.

Standard solution— Dissolve an accurately weighed quantity of USP Phenoxyethanol RSin Phenol solutionto obtain a solution having a known concentration of about 5mg of phenoxyethanol per mL.Accurately transfer 500µLof this solution to a vial,add 1000µLof isopropyl alcohol,crimp the vial,and mix on a vortex mixer for about 15seconds.

Test solution— Accurately transfer 500µLof Phenoxyethanol to a tared vial,and determine the weight of Phenoxyethanol taken.Add 1000µLof isopropyl alcohol,crimp the vial,and mix on a vortex mixer for about 15seconds.

Chromatographic system(see Chromatography á621ñ)— The gas chromatograph is equipped with a flame-ionization detector and a 0.32-mm ×10-m capillary column coated with a 5-µm film of stationary phase G27.The carrier gas is helium with a split flow rate of 44mLper minute.The injector port temperature and the detector temperature are both maintained at 300.The column temperature is programmed as follows:the starting column temperature is 80;after injection,it is increased to 260at a rate of 8per minute,then held for 10minutes.Chromatograph the Standard solution,and record the peak responses as directed for Procedure:the resolution,R,between phenol and phenoxyethanol peaks is not less than 10;and the relative standard deviation for replicate injections for the phenoxyethanol peak is not more than 2.0%.

Procedure— Separately inject equal volumes (about 1µL)of the Standard solutionand the Test solutioninto the chromatograph,record the chromatograms,and measure the peak area responses.Calculate the percentage of total impurities in the portion of Phenoxyethanol taken by the formula: in which Cis the concentration,in mg per mL,of phenoxyethanol in the Standard solution;Wis the weight of Phenoxyethanol,in mg,taken to prepare the Test solution;rUis the sum of all additional peak areas in the chromatogram obtained from the Test solution,excluding the main peak,the solvent peak,and the phenol peak;and rSis the peak area of the phenoxyethanol peak in the chromatogram obtained from the Standard solution:not more than 1.0%of total impurities is found.

Phenol solution and Chromatographic system— Prepare as directed under Chromatographic purity.

Standard preparation— Use the Standard solution,prepared as directed under Chromatographic purity.

Procedure— Separately inject equal volumes (about 1µL)of the Standard preparationand the Assay preparationinto the chromatograph,record the chromatograms,and measure the peak area responses.Calculate the quantity,in mg,of C8H10O2in the portion of Phenoxyethanol taken by the formula: in which Cis the concentration,in mg per mL,of USP Phenoxyethanol RSin the Standard preparation;and rUand rSare the responses of the phenoxyethanol peak obtained from the Assay preparationand the Standard preparation,respectively.NF23