»Zinc Gluconate contains not less than 97.0percent and not more than 102.0percent of C12H22O14Zn,calculated on the anhydrous basis.
Packaging and storage
Preserve in well-closed containers.
USP Reference standards á11ñ
USP Potassium Gluconate RS
Asolution (1in 10)responds to the tests for Zinc á191ñ
It responds to Identification
under Calcium Gluconate
between 5.5and 7.5,in a solution (1in 100).
Water,Method Ib á921ñ:
not more than 11.6%.
A1.0-g portion shows no more chloride than corresponds to 0.70mLof 0.020Nhydrochloric acid (0.05%).
A2.0-g portion shows no more sulfate than corresponds to 1.0mLof 0.020Nsulfuric acid (0.05%).
Dissolve 1.0g in 35mLof water:the limit is 3ppm.
Transfer 1.0g to a 250-mLconical flask,dissolve in 10mLof water,and add 25mLof alkaline cupric citrate TS.Cover the flask,boil gently for 5minutes,accurately timed,and cool rapidly to room temperature.Add 25mLof 0.6Nacetic acid,10.0mLof 0.1Niodine VS,and 10mLof 3Nhydrochloric acid,and titrate with 0.1Nsodium thiosulfate VS,adding 3mLof starch TSas the endpoint is approached.Perform a blank determination,omitting the specimen,and note the difference in volumes required.Each mLof the difference in volume of 0.1Nsodium thiosulfate consumed is equivalent to 2.7mg of reducing substances (as dextrose):the limit is 1.0%.
Limit of cadmium
Transfer 137.2mg of cadmium nitrate to a 1000-mLvolumetric flask,dissolve in water,dilute with water to volume,and mix.Pipet 25mLof the resulting solution into a 100-mLvolumetric flask,add 1mLof hydrochloric acid,dilute with water to volume,and mix.Each mLof this Standard preparation
contains 12.5µg of Cd.
Transfer 10.0g of Zinc Gluconate to a 50-mLvolumetric flask,dissolve in and dilute with water to volume,and mix.
To three separate 25-mLvolumetric flasks add,respectively,0,2.0,and 4.0mLof the Standard preparation.
To each flask add 5.0mLof the Test preparation,
dilute with water to volume,and mix.These test solutions contain,respectively,0,1.0,and 2.0µg per mLof cadmium from the Standard preparation.
Concomitantly determine the absorbances of the test solutions at the cadmium emission line at 228.8nm,with a suitable atomic absorption spectrophotometer (see Spectrophotometry and Light-scattering á851ñ
)equipped with a cadmium hollow-cathode lamp and an airacetylene flame,using water as the blank.Plot the absorbances of the test solutions versus their contents of cadmium,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 cadmium in each mLof the test solution containing 0mLof the Standard preparation.
Calculate the quantity,in ppm,of Cd in the specimen by multiplying this value by 25:the limit is 5ppm.
Limit of lead
For the preparation of all aqueous solutions and for the rinsing of glassware before use,employ water that has been passed through a strong-acid,strong-base,mixed-bed ion-exchange resin before use.Select all reagents to have as low a content of lead as practicable,and store all reagent solutions in containers of borosilicate glass.Cleanse glassware before use by soaking in warm 8Nnitric acid for 30minutes and by rinsing with deionized water.]
Ascorbic acidsodium iodide solution
Dissolve 20g of ascorbic acid and 38.5g of sodium iodide in water in a 200-mLvolumetric flask,dilute with water to volume,and mix.
Trioctylphosphine oxide solution
[CautionThis solution causes irritation.Avoid contact with eyes,skin,and clothing.Take special precautions in disposing of unused portions of solutions to which this reagent is added.
Dissolve 5.0g of trioctylphosphine oxide in 4-methyl-2-pentanone in a 100-mLvolumetric flask,dilute with the same solvent to volume,and mix.
Standard solutionand Blank
Transfer 5.0mLof Lead Nitrate Stock Solution
,prepared as directed in the test for Heavy Metals á231ñ
,to a 100-mLvolumetric flask,dilute with water to volume,and mix.Transfer 2.0mLof the resulting solution to a 50-mLvolumetric flask.To this volumetric flask and to a second,empty 50-mLvolumetric flask(Blank)
add 10mLof 9Nhydrochloric acid and about 10mLof water.To each flask add 20mLof Ascorbic acidsodium iodide solution
and 5.0mLof Trioctylphosphine oxide solution,
shake for 30seconds,and allow to separate.Add water to bring the organic solvent layer into the neck of each flask,shake again,and allow to separate.The organic solvent layers are the Blank
and the Standard solution,
and they contain 0.0µg and 2.0µg of lead per mL,respectively.
Add 1.0g of Zinc Gluconate,10mLof 9Nhydrochloric acid,about 10mLof water,20mLof Ascorbic acidsodium iodide solution,
and 5.0mLof Trioctylphosphine oxide solution
to a 50-mLvolumetric flask,shake for 30seconds,and allow to separate.Add water to bring the organic solvent layer into the neck of the flask,shake again,and allow to separate.The organic solvent layer is the Test solution.
Concomitantly determine the absorbances of the Blank,Standard solution,
and Test solution
at the lead emission line at 283.3nm,with a suitable atomic absorption spectrophotometer (see Spectrophotometry and Light-Scattering á851ñ
)equipped with a lead hollow-cathode lamp and an airacetylene flame,using the Blank
to set the instrument to zero.In a suitable analysis,the absorbance of the Standard solution
and the absorbance of the Blank
are significantly different:the absorbance of the Test solution
does not exceed that of the Standard solution
Organic volatile impurities,Method Iá467ñ:
meets the requirements.
Dissolve about 700mg of Zinc Gluconate,accurately weighed,in 100mLof water.Add 5mLof ammoniaammonium chloride buffer TSand 0.1mLof eriochrome black TS,and titrate with 0.05Medetate disodium VSuntil the solution is deep blue in color.Each mLof 0.05Medetate disodium is equivalent to 22.78mg of C12
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