A: The retention time of the major peak for chlorhexidine in the chromatogram of the Assay preparationcorresponds to that in the chromatogram of the Standard preparation,as obtained in the Assay.

B: To a volume of Oral Rinse,equivalent to about 10mg of chlorhexidine gluconate,add 5mLof a solution of cetyltrimethylammonium bromide (1in 100),1mLof 10Nsodium hydroxide,and 1mLof bromine TS:a deep red color is produced.

C: Undiluted Oral Rinse used as the test solution meets the requirements for Identificationtest Bunder Calcium Gluconate,except that a Standard solution containing about 0.6mg of USP Potassium Gluconate RSper mLis used and 15µLof the test solution and the Standard solution are applied to the thin-layer chromatographic plate.

Solution A,Solution B,Mobile phase,Diluent,System suitability solution,and Chromatographic system— Proceed as directed in the Assayunder Chlorhexidine Gluconate Solution.

Standard solutions— Prepare as directed for Standard solutionsin the test for Limit of p-chloroanilineunder Chlorhexidine Gluconate Solution.

Test solution— Transfer 10.0mLof Oral Rinse to a 25-mLvolumetric flask,dilute with Diluentto volume,and mix.

Procedure— Proceed as directed in the test for Limit of p-chloroanilineunder Chlorhexidine Gluconate Solution.Calculate the quantity,in µg per mL,of p-chloroaniline in the Oral Rinse taken by the formula: The limit is 3.0µg per mL.

Internal standard solution— Dilute 25mLof n-propyl alcohol with water to 500mL.

Standard solution— Transfer about 0.25g of dehydrated alcohol,accurately weighed,to a 28-mLscrew capped vial containing about 3mLof water.Add 5.0mLof Internal standard solution,and dilute with water to almost fill the vial.Cap the vial,and using a vortex mixer,mix for 15seconds.

Test solution— Transfer about 2.5g of Oral Rinse,accurately weighed,to a 28-mLscrew-capped vial.Add 5.0mLof Internal standard solution,and dilute with water to almost fill the vial.Cap the vial,and using a vortex mixer,mix for 15seconds.

Chromatographic system (see Chromatography á621ñ)— The gas chromatograph is equipped with a flame-ionization detector and a 0.53-mm ×30-m column,the internal wall of which is coated with a 1.5-µm film of liquid phase G27.The column is maintained at about 150between periods of use.The injection port is equipped with a split injection port with a split ratio of 10:1.The injection port and the detector block temperatures are maintained at about 250and 275,respectively.At the time of use the initial column temperature is maintained at about 35until the alcohol peaks elute,then is increased at a rate of 30per minute to a final temperature of about 225.The carrier gas is helium.Chromatograph the Standard solution,and record the peak responses as directed for Procedure:the relative retention times are 1.0for alcohol and about 1.5for n-propyl alcohol;the resolution,R,between alcohol and n-propyl alcohol is not less than 2;the tailing factor for the alcohol peak is not more than 3.0;and the relative standard deviation for replicate injections is not more than 2%.

Procedure— Separately inject equal volumes (about 0.5µL)of the Standard solutionand the Test solutioninto the chromatograph,record the chromatograms,and measure the responses for the major peaks.Calculate the percentage of alcohol (C2H5OH)in the Oral Rinse taken by the formula: in which WSis the weight,in g,of dehydrated alcohol taken to prepare the Standard solution;WUis the weight,in g,of Oral Rinse taken to prepare the Test solution;and RUand RSare the peak response ratios of alcohol to n-propyl alcohol obtained from the Test solutionand the Standard solution,respectively:between 90.0%and 115.0%of the labeled amount of alcohol (C2H5OH)is found.

Solution A,Solution B,Mobile phase,Diluent,System suitability solution,Standard preparation,and Chromatographic system— Proceed as directed in the Assayunder Chlorhexidine Gluconate Solution.

Assay preparation— Transfer 5.0mLof Oral Rinse to a 100-mLvolumetric flask,dilute with Diluentto volume,and mix.

Procedure— Proceed as directed in the Assayunder Chlorhexidine Gluconate Solution.Calculate the percentage (w/v)of chlorhexidine gluconate (C22H30Cl2N10·2C6H12O7)in the Oral Rinse taken by the formula: in which the terms are as defined therein.