(Official January 1, 2007)

Sodium chloride solution— Dissolve 1.8 g of sodium chloride in water, dilute with water to 2000 mL, and mix.

Manganese stock solution— Transfer 1.000 g of manganese to a 1000-mL volumetric flask, dissolve in 20 mL of nitric acid, dilute with 0.1 N hydrochloric acid to volume, and mix. This solution contains 1000 µg of manganese per mL. Store in a polyethylene bottle.

Standard preparations— Pipet 10 mL of the Manganese stock solution into a 500-mL volumetric flask, dilute with water to volume, and mix. Transfer 4.0, 5.0, and 6.0 mL, respectively, of this solution to separate 50-mL volumetric flasks, containing 10 mL of Sodium chloride solution, dilute the contents of each flask with water to volume, and mix. These Standard preparations contain, respectively, 1.6, 2.0, and 2.4 µg of manganese per mL.

Assay preparation— Transfer an accurately measured volume of Injection, equivalent to about 1 mg of manganese, to a 100-mL volumetric flask, dilute with water to volume, and mix. Pipet 10 mL of this solution into a 50-mL volumetric flask. From the labeled amount of sodium chloride, if any, in the Injection, calculate the amount, in mg, of sodium chloride in the initial dilution, and add sufficient Sodium chloride solution to bring the total sodium chloride content in this flask to 9 mg. Dilute with water to volume, and mix.

Procedure— Concomitantly determine the absorbances of the Standard preparations and the Assay preparation at the manganese emission line of 279 nm, with a suitable atomic absorption spectrophotometer (see Spectrophotometry and Light-scattering 851) equipped with a manganese hollow-cathode lamp and an air–acetylene flame, using a dilution of Sodium chloride solution (1:5) as the blank. Plot the absorbances of the Standard preparations versus concentration, in µg per mL, of manganese, and draw the straight line best fitting the three plotted points. From the graph so obtained, determine the concentration, in µg per mL, of manganese in the Assay preparation. Calculate the quantity, in mg, of manganese in each mL of the Injection taken by the formula: in which C is the concentration, in µg per mL, of manganese in the Assay preparation; and V is the volume, in mL, of Injection taken.