Assay
Sodium chloride solution
Dissolve 2.7g of sodium chloride in water,dilute with water to 2000mL,and mix.
Copper stock solution
Transfer 1.000g of copper to a 1000-mLvolumetric flask,dissolve in 20mLof nitric acid,dilute with 0.2Nnitric acid to volume,and mix.This solution contains 1000µg of copper per mL.Store in a polyethylene bottle.
Standard preparations
Pipet 15mLof Copper stock solutioninto a 250-mLvolumetric flask,dilute with water to volume,and mix.Transfer 4.0,5.0,and 6.0mLof this solution to separate 100-mLvolumetric flasks containing 10mLof Sodium chloride solution,dilute the contents of each flask with water to volume,and mix.These Standard preparationscontain,respectively,2.4,3.0,and 3.6µg of copper per mL.
Assay preparation
Transfer an accurately measured volume of Injection,equivalent to about 2mg of copper,to a 100-mLvolumetric flask,dilute with water to volume,and mix.Pipet 15mLof this solution into a 100-mLvolumetric 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 solutionto bring the total sodium content of this flask to 13.5mg.Dilute with water to volume,and mix.
Procedure
Concomitantly determine the absorbances of the
Standard preparationsand the
Assay preparationat the copper emission line of 324.8nm,with a suitable atomic absorption spectrophotometer (see
Spectrophotometry and Light-scattering á851ñ)equipped with a copper hollow-cathode lamp and an airacetylene flame using a 1in 10dilution of
Sodium chloride solutionas the blank.Plot the absorbances of the
Standard preparationsversus concentration,in µg per mL,of copper,and draw the straight line best fitting the three plotted points.From the graph so obtained,determine the concentration,in µg per mL,of copper in the
Assay preparation.Calculate the quantity,in mg,of copper in each mLof the Injection taken by the formula:
2C/3V,
in which
Cis the concentration,in µg per mL,of copper in the
Assay preparation;and
Vis the volume,in mL,of Injection taken.