Na2HPO4·xH2O(anhydrous) 141.96

Phosphoric acid,disodium salt,dodecahydrate.
Disodium hydrogen phosphate,dodecahydrate 358.14 [10039-32-4].

Phosphoric acid,disodium salt,heptahydrate.
Disodium hydrogen phosphate heptahydrate 268.07 [7782-85-6].

Phosphoric acid,disodium salt,dihydrate.
Disodium hydrogen phosphate,dihydrate 177.99 [10028-24-7].

Phosphoric acid,sodium salt,monohydrate.
Disodium hydrogen phosphate,monohydrate 159.94 [118830-14-1].

Phosphoric acid,disodium salt,hydrate.
Disodium hydrogen phosphate hydrate [10140-65-5].

Anhydrous [7558-79-4].

Packaging and storage— Preserve in tight containers.

Labeling— Label it to indicate whether it is dried or is the monohydrate,the dihydrate,the heptahydrate,or the dodecahydrate.

Identification— Asolution (the equivalent of 1part of Na2HPO4in 30)responds to the tests for Sodium á191ñand for Phosphate á191ñ.

Loss on drying á731ñ— Dry it at 130to constant weight:the dried form loses not more than 5.0%of its weight,the monohydrate loses between 10.3%and 12.0%of its weight,the dihydrate loses between 18.5%and 21.5%of its weight,the heptahydrate loses between 43.0%and 50.0%of its weight,and the dodecahydrate loses between 55.0%and 64.0%of its weight.

Insoluble substances— Dissolve the equivalent of 5.0g of Na2HPO4in 100mLof hot water,filter through a tared filtering crucible,wash the insoluble residue with hot water,and dry at 105for 2hours:the weight of the residue so obtained does not exceed 20mg (0.4%).

Chloride á221ñ— Aportion equivalent to 0.5g of Na2HPO4shows no more chloride than corresponds to 0.42mLof 0.020Nhydrochloric acid (0.06%).

Sulfate á221ñ— Aportion equivalent to 0.1g of Na2HPO4shows no more sulfate than corresponds to 0.2mLof 0.020Nsulfuric acid (0.2%).

Arsenic,Method Iá211ñ— Prepare a Test Preparationby dissolving a portion equivalent to 187.5mg of Na2HPO4in 35mLof water:the limit is 16ppm.

Heavy metals á231ñ— Dissolve a portion equivalent to 2.1g of Na2HPO4in enough water to make 50mLof stock solution.Transfer 12mLof this stock solution to a 50-mLcolor-comparison tube (Test Preparation).Transfer 11mLof the stock solution to a second color-comparison tube containing 1.0mLof Standard Lead Solution(Monitor Preparation).Transfer 1.0mLof Standard Lead Solutionand 11mLof water to a third color-comparison tube (Standard Preparation).Proceed as directed for Procedure,omitting the dilution to 50mL:the limit is 0.002%.

Assay— Transfer 40.0mLof 1Nhydrochloric acid to a 250-mLbeaker,add 50mLof water,and titrate potentiometrically with 1Nsodium hydroxide VSto the endpoint.Record the volume of 1Nsodium hydroxide VSconsumed as the blank.Transfer a portion of Dibasic Sodium Phosphate,accurately weighed,equivalent to about 2.5g of Na2HPO4,to a 250-mLbeaker,add 40.0mLof the 1Nhydrochloric acid and 50mLof water,and stir until dissolved.Titrate the excess acid potentiometrically with 1Nsodium hydroxide VSto the inflection point at about pH4,and record the buret reading.Subtract this buret reading from that of the blank,and designate the volume of 1Nsodium hydroxide VSresulting from this subtraction as A.Continue the titration with 1Nsodium hydroxide VSto the inflection point at about pH8.8,record the buret reading,and calculate the volume (B)of 1Nsodium hydroxide required in the titration between the two inflection points (pH4to pH8.8).Where Ais equal to or less than B,each mLof the volume Aof 1Nsodium hydroxide is equivalent to 142.0mg of Na2HPO4.Where Ais greater than B,each mLof the volume 2B-Aof 1Nsodium hydroxide is equivalent to 142.0mg of Na2HPO4.

Expert Committee:(PA4)Pharmaceutical Analysis 4

USP28–NF23Page 1790

Phone Number:1-301-816-8251