A: It meets the requirements of the tests for Sodium 191 and for Magnesium 191.

B: To 10 mL of the Irrigation add 1 mL of mercuric sulfate TS, heat to boiling, and add a few drops of potassium permanganate TS: a white precipitate is formed.

Mobile phase— Add 2.0 mL of sulfuric acid to 800 mL of water, mix, and dilute with water to 1000 mL. Pass through a membrane filter, heat to 40, and degas. Maintain the temperature of the Mobile phase at 40 throughout the analysis.

Standard preparation— Dissolve a suitable quantity of anhydrous citric acid, accurately weighed, in water to obtain a solution having a known concentration of about 1.2 mg per mL.

Resolution solution— Prepare a solution in water containing about 1 mg of citric acid and about 2 mg of boric acid per mL.

Assay preparation— Transfer an accurately measured volume of Irrigation, equivalent to about 130 mg of citric acid monohydrate, to a 100-mL volumetric flask, dilute with water to volume, and mix.

Chromatographic system (see Chromatography 621)— The liquid chromatograph is equipped with a refractive index detector and a 7.8-mm × 30-cm column that contains packing L17. The column temperature is maintained at 40. The flow rate is about 0.6 mL per minute. Chromatograph the Resolution solution, and record the peak responses as directed for Procedure: the resolution, R, between citric acid and boric acid is not less than 4.0. Chromatograph the Standard preparation, and record the peak responses as directed for Procedure: the relative standard deviation for replicate injections is not more than 1.5%.

Procedure— Separately inject equal volumes (about 50 µL) of the Standard preparation and the Assay preparation into the chromatograph, record the chromatograms, and measure the responses for the major peaks. Calculate the quantity, in mg, of C6H8O7·H2O in each mL of the Irrigation taken by the formula: in which 210.14 and 192.12 are the molecular weights of citric acid monohydrate and anhydrous citric acid, respectively; C is the concentration, in mg per mL, of anhydrous citric acid in the Standard preparation; V is the volume, in mL, of Irrigation taken; and rU and rS are the peak responses for citric acid obtained from the Assay preparation and the Standard preparation, respectively.

Mobile Phase, Standard Preparation 1, and Chromatographic System— Proceed as directed under Assay for Citric Acid/Citrate and Phosphate 345.

Assay preparation— Transfer an accurately measured volume of Irrigation, equivalent to about 130 mg of monohydrate citric acid into a suitable volumetric flask, and proceed as directed for Assay Preparation for Citric Acid/Citrate Assay under Assay for Citric Acid/Citrate and Phosphate 345.

Procedure— Proceed as directed for Procedure under 345, and calculate the quantity, in mg per mL, of monohydrate citric acid (C6H8O7·H2O) in the Irrigation taken by the formula: in which 210.14 is the molecular weight of citric acid monohydrate; 189.10 is the molecular weight of citrate (C6H5O7); CS is the concentration, in µg per mL, of citrate in Standard Preparation 1; D is the dilution factor; V is the volume, in mL, of Irrigation used to prepare the Assay preparation; and rU and rS are the citrate peak areas obtained from the Assay preparation and Standard Preparation 1, respectively.

Sodium chloride stock solution— Transfer 475 mg of sodium chloride, previously dried at 105 for 2 hours and accurately weighed, to a 100-mL volumetric flask. Dissolve in water, dilute with water to volume, and mix.

Internal standard solution— Transfer 636 mg of lithium chloride to a 1000-mL volumetric flask, dissolve in and dilute with water to volume, and mix.

Standard preparation— Quantitatively prepare a mixture of Internal standard solution and Sodium chloride stock solution (99:1).

Assay preparation— Dilute an accurately measured volume of Irrigation quantitatively with water to obtain a stock solution containing about 4.4 mg of sodium carbonate per mL. Quantitatively prepare a mixture of Internal standard solution and this stock solution (99:1).

Procedure— Concomitantly determine the emittances of the Standard preparation and the Assay preparation at 591 nm and 671 nm with a suitable flame photometer, adjusting the instrument to zero emittance with Internal standard solution. Calculate the quantity, in mg, of Na2CO3 in each mL of the Irrigation taken by the formula: in which 105.99 is the molecular weight of sodium carbonate; 116.88 is two times the molecular weight of sodium chloride; C is the concentration, in mg per mL, of sodium chloride in the Sodium chloride stock solution; L is the labeled quantity, in mg per mL, of sodium carbonate in the Irrigation; D is the concentration, in mg per mL, of sodium carbonate in the stock solution used to prepare the Assay preparation, on the basis of the labeled quantity in each mL, and the extent of dilution; RU,591 and RU,671 are the emittance readings obtained from the Assay preparation at the wavelengths indicated by the subscripts; and RS,671 and RS,591 are the emittance readings obtained from the Standard preparation at the wavelengths indicated by the subscripts.