NOTE—Commercially available atomic absorption standard solutions for the minerals,where applicable,may be used where preparation of a standard stock solution is described in the following Assays.Use deionized water where water is specified.Where atomic absorption spectrophotometry is specified in the Assay,the concentrations of the Standard preparationsand the Assay preparationmay be modified to fit the linear or working range of the instrument.

Copper standard stock solution— Dissolve 1.00g of copper foil,accurately weighed,in a minimum volume of a 50%(v/v)nitric acid solution,and dilute with a 1%(v/v)nitric acid solution to 1000mLto obtain a solution having a known concentration of about 1000µg of copper per mL.

Standard preparations— Transfer 10.0mLof Copper standard stock solutionto a 100-mLvolumetric flask,and quantitatively dilute with 0.125Nhydrochloric acid to volume to obtain a standard solution having a known concentration of about 100µg of copper per mL.To separate 200-mLvolumetric flasks,transfer 1.0,2.0,4.0,6.0,and 8.0mLof the standard solution,dilute with water to volume,and mix to obtain solutions having known concentrations of about 0.5,1.0,2.0,3.0,and 4.0µg of copper per mL.

Assay preparation— Weigh and finely powder not fewer than 20Tablets.Transfer an accurately weighed portion of the powder,equivalent to about 5mg of copper,to a porcelain crucible.Proceed as directed for Assay preparationin the Assay for calciumunder Calcium with Vitamin D Tablets,except to prepare the Assay preparationto contain about 2µg of copper per mLand to omit the use of the Lanthanum chloride solution.

Procedure— Concomitantly determine the absorbances of the Standard preparationsand the Assay preparationat the copper emission line at 324.7nm with an atomic absorption spectrophotometer (see Spectrophotometry and Light-Scattering á851ñ)equipped with a copper hollow-cathode lamp and an air–acetylene flame,using 0.125Nhydrochloric acid as the blank.Plot the absorbances of the Standard preparationsversus concentration,in µg per mL,of copper,and draw the straight line best fitting the five plotted points.From the graph so obtained,determine the concentration,C,in µg per mL,of copper in the Assay preparation.Calculate the quantity,in mg,of copper (Cu)in the portion of Tablets taken by the formula: in which Dis the dilution factor used to prepare the Assay preparation.

Lanthanum chloride solution— Dissolve 26.7g of lanthanum chloride in 0.125Nhydrochloric acid to make 100mL.

Magnesium standard stock solution— Transfer 1.00g of magnesium,accurately weighed,to a 1000-mLvolumetric flask,dissolve in 50mLof 6Nhydrochloric acid,dilute with water to volume,and mix to obtain a solution having a known concentration of about 1000µg of magnesium per mL.

Standard preparations— Quantitatively dilute a volume of the Magnesium standard stock solutionwith 0.125Nhydrochloric acid to obtain a standard solution having a concentration of about 20µg of magnesium per mL.To separate 100-mLvolumetric flasks,transfer 1.0,1.5,2.0,2.5,and 3.0mLof standard solution.To each flask add 1.0mLof Lanthanum chloride solution,dilute with 0.125Nhydrochloric acid to volume,and mix to obtain solutions having known concentrations of about 0.2,0.3,0.4,0.5,and 0.6µg of magnesium per mL.

Assay preparation— Weigh and finely powder not fewer than 20Tablets.Transfer an accurately weighed portion of the powder,equivalent to about 200mg of magnesium,to a porcelain crucible.Heat for 6to 12hours in a muffle furnace maintained at about 550,and cool.Add about 15mLof hydrochloric acid,and boil gently on a hot plate or a steam bath for about 30minutes,intermittently rinsing the inner surface of the crucible with 6Nhydrochloric acid.Cool,and quantitatively transfer the contents of the crucible to a 100-mLvolumetric flask,rinsing the crucible with portions of 6Nhydrochloric acid.Dilute the contents of the flask with water to volume,mix,and filter,discarding the first 5mLof the filtrate.Dilute the filtrate quantitatively,and stepwise if necessary,with 0.125Nhydrochloric acid to obtain a solution having a concentration of about 0.4µg of magnesium per mL,adding 1mLof Lanthanum chloride solutionper 100mLof the final volume.

Procedure— Concomitantly determine the absorbances of the Standard preparationsand the Assay preparationat the magnesium emission line at 285.2nm with an atomic absorption spectrophotometer (see Spectrophotometry and Light-Scattering á851ñ)equipped with a magnesium hollow-cathode lamp and an air–acetylene flame,using 0.125Nhydrochloric acid containing 0.1%of Lanthanum chloride solutionas the blank.Plot the absorbances of the Standard preparationsversus concentration,in µg per mL,of magnesium,and draw the straight line best fitting the five plotted points.From the graph so obtained,determine the concentration,C,in µg per mL,of magnesium in the Assay preparation.Calculate the quantity,in mg,of magnesium (Mg)in the portion of Tablets taken by the formula: in which Dis the dilution factor used to prepare the Assay preparation.

Manganese standard stock solution— Transfer 1.00g of manganese,accurately weighed,to a 1000-mLvolumetric flask,dissolve in 20mLof nitric acid,dilute with 6Nhydrochloric acid to volume,and mix to obtain a solution having a known concentration of about 1000µg of manganese per mL.

Standard preparations— Quantitatively dilute 10.0mLof the Manganese standard stock solutionwith 0.125Nhydrochloric acid to 200.0mLto obtain a standard solution having a concentration of about 50µg of manganese per mL.To separate 100-mLvolumetric flasks transfer 1.0,1.5,2.0,3.0,and 4.0mLof the standard solution,dilute the contents of each flask with 0.125Nhydrochloric acid to volume,and mix to obtain solutions having known concentrations of about 0.5,0.75,1.0,1.5,and 2.0µg of manganese per mL.

Assay preparation— Weigh and finely powder not fewer than 20Tablets.Transfer an accurately weighed portion of the powder,equivalent to about 9mg of manganese,to a porcelain crucible.Proceed as directed for Assay preparationin the Assay for calciumunder Calcium with Vitamin D Tablets,except to prepare the Assay preparationto contain 1µg of manganese per mLand to omit the use of the Lanthanum chloride solution.

Procedure— Concomitantly determine the absorbances of the Standard preparationsand the Assay preparationat the manganese emission line at 279.5nm with an atomic absorption spectrophotometer (see Spectrophotometry and Light-Scattering á851ñ)equipped with a manganese hollow-cathode lamp and an air–acetylene flame,using 0.125Nhydrochloric acid as the blank.Plot the absorbances of the Standard preparationsversus concentration,in µg per mL,of manganese,and draw the straight line best fitting the five plotted points.From the graph so obtained,determine the concentration,C,in µg per mL,of manganese in the Assay preparation.Calculate the weight,in mg,of manganese (Mn)in the portion of Tablets taken by the formula: in which Dis the dilution factor used to prepare the Assay preparation.

Zinc standard stock solution— Transfer about 311mg of zinc oxide,accurately weighed,to a 250-mLvolumetric flask,add 80mLof 5Mhydrochloric acid,warm,if necessary,to dissolve,and cool.Dilute with water to volume,and mix to obtain a solution having a known concentration of about 1000µg of zinc per mL.

Standard preparations— Dilute a volume of the Zinc standard stock solutionquantitatively,and stepwise if necessary,with 0.125Nhydrochloric acid to obtain a standard solution having a known concentration of about 50µg of zinc per mL.To separate 100-mLvolumetric flasks transfer 1.0,2.0,3.0,4.0,and 5.0mLof this solution.Dilute the contents of each flask with 0.125Nhydrochloric acid to volume,and mix to obtain solutions having known concentrations of about 0.5,1.0,1.5,2.0,and 2.5µg of zinc per mL.

Assay preparation— Weigh and finely powder not fewer than 20Tablets.Transfer an accurately weighed portion of the powder,equivalent to about 40mg of zinc,to a porcelain crucible.Proceed as directed for Assay preparationin the Assay for calciumunder Calcium with Vitamin D Tablets,except to prepare the Assay preparationto contain 2µg of zinc per mLand to omit the use of the Lanthanum chloride solution.

Procedure— Concomitantly determine the absorbances of the Standard preparationsand the Assay preparationat the zinc emission line at 213.8nm with an atomic absorption spectrophotometer (see Spectrophotometry and Light-Scattering á851ñ)equipped with a zinc hollow-cathode lamp and an air–acetylene flame,using 0.125Nhydrochloric acid as the blank.Plot the absorbances of the Standard preparationsversus concentration,in µg per mL,of zinc,and draw the straight line best fitting the five plotted points.From the graph so obtained,determine the concentration,C,in µg per mL,of zinc in the Assay preparation.Calculate the quantity,in mg,of zinc (Zn)in the portion of Tablets taken by the formula: in which Dis the dilution factor used to prepare the Assay preparation.