A: The Assay preparation,prepared as directed in the Assay,exhibits an absorption maximum at about 313nm when tested as directed for Procedurein the Assay.

B: Add 0.3mLof alkaline mercuric-potassium iodide TSto 5mLof Injection:a reddish-brown color develops.

C: Evaporate 50mLof Injection on a steam bath to a volume of about 0.3mL,and add 0.3mLof ammonium hydroxide.Cool,and add slowly,with mixing,a well-cooled mixture of 1mLof nitric acid and 1.2mLof water.Allow to stand for 24to 48hours,and pass through a sintered-glass filter.To the filtrate add 0.5mLof dibasic sodium phosphate TS:a yellow precipitate is formed,and it dissolves in an excess of 6Nammonium hydroxide.

Ammonium hydroxide diluent— Dilute 40mLof ammonium hydroxide with water to 1000mL.Store in a plastic bottle.

Sodium sulfate solution— Dissolve 1g of sodium sulfate in water to make 100mL.

Molybdenum stock solution— Transfer about 1.84g of previously assayed Ammonium Molybdate,accurately weighed,to a 1000-mLvolumetric flask,dilute with Ammonium hydroxide diluentto volume,and mix.This solution contains the equivalent of 1000µg of molybdenum per mL.

Standard preparations— Transfer 0,1.0,2.0,3.0,and 4.0mL,respectively,of Molybdenum stock solutionto separate 100-mLvolumetric flasks,and to the respective flasks add 5.0,4.0,3.0,2.0,and 1.0mLof Ammonium hydroxide diluent.To each flask add 10mLof Sodium sulfate solution,dilute with water to volume,and mix.These Standard preparationscontain,respectively,0,10,20,30,and 40µg of molybdenum per mL.

Assay preparation— Transfer an accurately measured volume of Injection,equivalent to about 500µg of molybdenum,to a 25-mLvolumetric flask,add 1.25mLof Ammonium hydroxide diluentand 2.5mLof Sodium sulfate solution,dilute with water to volume,and mix.

Procedure— Concomitantly determine the absorbances of the Standard preparationsand the Assay preparationat the molybdenum emission line of 313.3nm with a suitable atomic absorption spectrophotometer (see Spectrophotometry and Light-scattering á851ñ)equipped with a molybdenum hollow-cathode lamp and a nitrous oxide–acetylene reducing flame,using water as the blank.Plot the absorbances of the Standard preparationsversus concentration,in µg per mL,of molybdenum,and draw the straight line best fitting the five plotted points.From the graph so obtained,determine the concentration,in µg per mL,of molybdenum in the Assay preparation.Calculate the quantity,in µg,of molybdenum (Mo)in each mLof the Injection taken by the formula: in which Cis the concentration,in µg per mL,of molybdenum in the Assay preparation;and Vis the volume,in mL,of Injection taken.