A: Infrared Absorption á197Kñ.

B: Asolution (1in 20)meets the requirements of the tests for Chloride á191ñ.

Ammonium hydroxide–sodium hydroxide solution— Transfer 8.4g of sodium hydroxide solution (1in 2)to a plastic bottle,add 100mLof ammonium hydroxide,and mix.

Standard solution— Transfer 1.0mLof the Diluted Standard Lead Solutionto a separatory funnel containing 25.0mLof water.

Test solution— Dissolve 3.00g in a separatory funnel containing 25.0mLof water.

Procedure— Separately add 6.0mLof Ammonium Citrate Solutionand 3.0mLof Potassium Cyanide Solutionto the Standard solutionand the Test solution.Extract each of the resulting solutions three times with 5.0-mLportions of Dithizone Extraction Solution,shaking for 60seconds and draining off each extract into another separator.Shake the combined dithizone solutions for 30seconds with 20.0mLof nitric acid (1in 100),and discard the methylene chloride layer.Add 6.0mLof Ammonia Cyanide Solution,2mLof Ammonium hydroxide–sodium hydroxide solution,and 10mLof Standard Dithizone Solution,and shake for 45seconds.Allow the phases to separate,and measure the absorbance of the lower layer at 510nm with a suitable spectrophotometer.The absorbance of the Test solutionis not more than the absorbance of the Standard solution:not more than 0.3µg per g is found.

Standard solution— Dissolve an accurately weighed quantity of trimethylamine hydrochloride in water,and dilute quantitatively,and stepwise if necessary,to obtain a solution having a known concentration of 500µg per mL.

Test solution— Transfer 10.0g of Choline Chloride to a beaker containing a plastic-coated stirring bar,add 170mLof water and 30.0mLof sodium hydroxide TS,and stir until dissolved.

System suitability solution— Dissolve an accurately weighed quantity of trimethylamine hydrochloride in water,and dilute quantitatively,and stepwise if necessary,to obtain a solution containing 10µg of trimethylamine hydrochloride per mL.Transfer 10.0mLof this solution to a beaker containing a plastic-coated stirring bar,add 170mLof water and 30.0mLof sodium hydroxide TS,and stir until dissolved.

Electrode system— Use a gas-sensing,ammonia-specific indicating electrode with internal reference connected to a pHmeter capable of measuring potentials with a minimum reproducibility of ±0.1mV(see pHá791ñ).

Standard response line— Transfer 30.0mLof sodium hydroxide TSto a suitable beaker,and add enough water to give a total volume of 200mL.Add a plastic-coated stirring bar,insert the electrode into the solution,and record the potential,in mV.Continue stirring,and at 5-minute intervals add 0.200,0.600,1.00,and 2.00mLof Standard solution,and record the potential after each addition.Plot the logarithms of the cumulative trimethylamine concentrations (0.50,1.50,2.50,and 5.00µg per mL)versus potential,in mV,and determine the slope (S)of the Standard response linefor the electrode.

System suitability— Proceed with the System suitability solutionas directed for Test solutionfor Procedureand measure the potentials:the trimethylamine equivalent is between 8.5and 11.5mg per liter.

Procedure— Rinse the electrode,insert it into the Test solution,stir,and record the potential,in mV.Add 0.100mLof the Standard solution,and record the potential.Add another 0.100mLof the Standard solution,and record the potential.[NOTE—If the total change after the second addition of the Standard solutionis less than 10mV,add a third aliquot of 0.200mL.]Calculate the quantity,in µg per g,of total amines in the portion of Choline Chloride taken by the formula: in which Vais the total volume of the Standard solutionadded to the Test solution;Wis the weight,in g,of Choline Chloride taken to prepare the Test solution;and the correction factor,F,is calculated by the formula: in which mVois the initial reading,in mV,of the Test solution;mVfis the final reading,in mV,after the additions of the Standard solution;and Sis the slope of the Standard response linefor the electrode:not more than 0.001%is found.

Buffer solution— Dissolve 7.1g of anhydrous dibasic sodium phosphate in 1liter of water.Adjust with phosphoric acid to a pHof 2.5.

Mobile phase— Prepare a filtered and degassed mixture of Buffer solutionand acetonitrile (50:50).

Standard solution— Transfer an accurately weighed amount,not more than 100mg,of USP Choline Chloride RSto a 24-mLscrew-capped vial,and add 400mg of 3,5-dinitrobenzoyl chloride and 10mLof acetonitrile.Cap the vial,heat to 55,and continue heating for 1hour.Cool to room temperature,and add 5mLof water.Allow to stand for 2minutes.Quantitatively transfer the solution to a 25-mLvolumetric flask,dilute with acetonitrile to volume,and mix.Dilute a volume of this solution with Mobile phaseto obtain a solution having a known concentration of 2.0µg of USP Choline Chloride RSper mL.

Test solution— Transfer about 110mg of Choline Chloride,accurately weighed,to a 24-mLscrew-capped vial.Dry at 120for 2hours.Add 400mg of 3,5-dinitrobenzoyl chloride and 10mLof acetonitrile.Cap the vial,heat to 55,and continue heating for 1hour.Cool to room temperature,and add 5mLof water.Allow to stand for 2minutes.Quantitatively transfer the solution to a 50-mLvolumetric flask,dilute with Mobile phaseto volume,and mix.

Chromatographic system (see Chromatography á621ñ)— The liquid chromatograph is equipped with a 208-nm detector and a 4.6-mm ×25-cm column that contains packing L7.The column temperature is maintained at 30.The flow rate is about 1.0mLper minute.Chromatograph the Standard solution,and record the peak responses as directed for Procedure:the capacity factor,k¢,is not less than 2;and the relative standard deviation determined from the choline chloride derivative peak is not more than 5%.

Procedure— Separately inject equal volumes (about 20µL)of the Standard solutionand the Test solutioninto the chromatograph,record the chromatograms,and measure all of the peak responses.Calculate the percentage of each impurity in the portion of Choline Chloride taken by the formula: in which Cis the concentration,in mg per mL,of USP Choline Chloride RSin the Standard solution;Wis the weight,in mg,of Choline Chloride taken to prepare the Test solution;riis the peak response for each impurity,other than that for the choline chloride derivative and 3,5-dinitrobenzoic acid obtained from the Test solution;and rSis the peak response for the choline chloride derivative obtained from the Standard solution:not more than 0.3%of any individual impurity is found;and not more than 2.0%of total impurities is found.