pH6.0acetate buffer— Dissolve 50g of ammonium acetate in 150mLof water,adjust with glacial acetic acid to a pHof 6.0,dilute with water to 250mL,and mix.

Procedure— Dissolve 1.0g of it in 50mLof water,and add 5mLof pH6.0acetate buffer.Extract this solution with successive portions of 10,10,and 5mLof a 0.5%solution of 8-hydroxyquinoline in chloroform,combining the chloroform extracts in a 50-mLvolumetric flask.Dilute the combined extracts with chloroform to volume,and mix (test solution).Prepare a Standard solution from a mixture of 2.0mLof a solution containing 1.0µg of Al per mL,prepared as directed for Standard Preparationsunder Aluminum á206ñ,5mLof pH6.0acetate buffer,and 48mLof water,and extract as described above.Prepare a blank solution from a mixture of 50mLof water and 5mLof pH6.0acetate buffer,and extract as described above.Determine the fluorescence intensities of the test solution and the Standard solution in a fluorometer set at an excitation wavelength of 392nm and an emission wavelength of 518nm,using the blank solution to set the instrument to zero.The fluorescence of the test solution does not exceed that of the Standard solution (2µg per g).

Stock test solution— Dissolve 50g of it and 5g of ammonium acetate in 200mLof 1Nhydrochloric acid,and filter.The pHof this solution is between 4.5and 5.5.[NOTE—Cover the solution.]

Barium chloride solution— Dissolve an accurately weighed quantity of anhydrous barium chloride in water to obtain a solution having a concentration of 0.758mg per mL.This solution contains 500µg of barium per mL.

Test solutions— To four separate tubes add 1.0,1.5,2.0,and 2.5mLof Barium chloride solution.To each tube add a sufficient volume of the Stock test solutionto bring the volume to 40mL.

Standard solution— To a fifth tube add 1g of ammonium acetate,2mLof 1Nhydrochloric acid,3.0mLof Barium chloride solution,and sufficient water to bring the volume to 40mL.

Ammonium sulfate solution— Use a solution of ammonium sulfate (1in 10).

Procedure— To the Test solutionsand the Standard solutionadd,with brisk stirring,3.0mLof Ammonium sulfate solution,and allow to stand for 20minutes.The Test solutionscontaining 1.0and 1.5mLof Barium chloride solutionremain clear or are only faintly turbid.The Test solutioncontaining 2.0mLof Barium chloride solutionis not more turbid than the Standard solution.

Standard preparation— Dissolve an accurately weighed quantity of magnesium oxide in 1Nnitric acid to obtain a solution having a concentration of 1.516mg per mL.This solution contains 1000µg of magnesium per mL.Dilute an accurately measured volume of this solution quantitatively,and stepwise if necessary,with water to obtain a solution containing 5.0µg of magnesium per mL.

Test preparation— Transfer 200mg of Calcium Acetate to a 100-mLvolumetric flask,dissolve in and dilute with water to volume,and mix.

Procedure— To three separate 25-mLvolumetric flasks add 0,2.0,and 4.0mLof the Standard preparation.To each flask add 20.0mLof the Test preparation,dilute with water to volume,and mix.These test solutions contain,respectively,0,0.4,and 0.8µg per mLof magnesium from the Standard preparation.Concomitantly determine the absorbances of the test solutions at the magnesium emission line at 285.2nm with a suitable atomic absorption spectrophotometer (see Spectrophotometry and Light-Scattering á851ñ)equipped with an air–acetylene flame,using water as the blank.Plot the absorbances of the test solutions versus their contents of magnesium,in µg per mL,as furnished by the Standard preparation,draw the straight line best fitting the three points,and extrapolate the line until it intercepts the concentration axis.From the intercept determine the amount,in µg,of magnesium in each mLof the test solution containing 0mLof the Standard preparation.Calculate the percentage of magnesium in the specimen by multiplying this value by 0.0625:the limit is 0.05%.

Standard preparation— Transfer 5.959g of potassium chloride,previously dried at 105for 2hours and accurately weighed,to a 250-mLvolumetric flask,dilute with water to volume,and mix.This solution contains 12.5mg of potassium per mL.Dilute an accurately measured volume of this solution quantitatively,and stepwise if necessary,with water to obtain a solution containing 31.25µg of potassium per mL.

Test preparation— Transfer 1.25g of Calcium Acetate to a 100-mLvolumetric flask,dissolve in and dilute with water to volume,and mix.

Procedure— To three separate 25-mLvolumetric flasks add 0,2.0,and 4.0mLof the Standard preparation.To each flask add 20.0mLof the Test preparation,dilute with water to volume,and mix.These test solutions contain,respectively,0,2.5,and 5.0µg per mLof potassium from the Standard preparation.Concomitantly determine the absorbances of the test solutions at the potassium emission line at 766.7nm with a suitable atomic absorption spectrophotometer (see Spectrophotometry and Light-Scattering á851ñ)equipped with an air–acetylene flame,using water as the blank.Plot the absorbances of the test solutions versus their contents of potassium,in µg per mL,as furnished by the Standard preparation,draw the straight line best fitting the three points,and extrapolate the line until it intercepts the concentration axis.From the intercept determine the amount,in µg,of potassium in each mLof the test solution containing 0mLof the Standard preparation.Calculate the percentage of potassium in the specimen by multiplying this value by 0.01:the limit is 0.05%.

Standard preparation— Transfer 6.355g of sodium chloride,previously dried at 105for 2hours and accurately weighed,to a 250-mLvolumetric flask,dilute with water to volume,and mix.This solution contains 10.0mg of sodium per mL.Dilute an accurately measured volume of this solution quantitatively,and stepwise if necessary,with water to obtain a solution containing 250µg of sodium per mL.

Test preparation— Transfer 1.0g of Calcium Acetate to a 100-mLvolumetric flask,dissolve in and dilute with water to volume,and mix.

Procedure— To three separate 25-mLvolumetric flasks add 0,2.0,and 4.0mLof the Standard preparation.To each flask add 20.0mLof the Test preparation,dilute with water to volume,and mix.These test solutions contain,respectively,0,20.0,and 40.0µg per mLof sodium from the Standard preparation.Concomitantly determine the absorbances of the test solutions at the sodium emission line at 589.0nm with a suitable atomic absorption spectrophotometer (see Spectrophotometry and Light-Scattering á851ñ)equipped with an air–acetylene flame,using water as the blank.Plot the absorbances of the test solutions versus their contents of sodium,in µg per mL,as furnished by the Standard preparation,draw the straight line best fitting the three points,and extrapolate the line until it intercepts the concentration axis.From the intercept determine the amount,in µg,of sodium in each mLof the test solution containing 0mLof the Standard preparation.Calculate the percentage of sodium in the specimen by multiplying this value by 0.0125:the limit is 0.5%.

Standard preparation— Dissolve an accurately weighed quantity of strontium acetate in water to obtain a solution having a concentration of 2.45mg per mL.This solution contains 1000µg of strontium per mL.Dilute an accurately measured volume of this solution quantitatively,and stepwise if necessary,with water to obtain a solution containing 50.0µg of strontium per mL.

Test preparation— Transfer 2.0g of Calcium Acetate to a 100-mLvolumetric flask,dissolve in and dilute with water to volume,and mix.

Procedure— To three separate 25-mLvolumetric flasks add 0,2.0,and 4.0mLof the Standard preparation.To each flask add 20.0mLof the Test preparation,dilute with water to volume,and mix.These test solutions contain,respectively,0,4.0,and 8.0µg per mLof strontium from the Standard preparation.Concomitantly determine the absorbances of the test solutions at the strontium emission line at 460.7nm with a suitable atomic absorption spectrophotometer (see Spectrophotometry and Light-Scattering á851ñ)equipped with a nitrous oxide–acetylene flame,using water as the blank.Plot the absorbances of the test solutions versus their contents of strontium,in µg per mL,as furnished by the Standard preparation,draw the straight line best fitting the three points,and extrapolate the line until it intercepts the concentration axis.From the intercept determine the amount,in µg,of strontium in each mLof the test solution containing 0mLof the Standard preparation.Calculate the percentage of strontium in the specimen by multiplying this value by 0.00625:the limit is 0.05%.