Methylparaben Sodium
»Methylparaben Sodium contains not less than 98.5percent and not more than 101.5percent of C8H7NaO3,calculated on the anhydrous basis.
Packaging and storage— Preserve in tight containers.
Completeness of solution á641ñ— One g of it,dissolved in water,meets the requirement.
Identification—
A: Dissolve 0.5g in 5mLof water,acidify with hydrochloric acid,and filter the resulting precipitate.Wash the precipitate with water,and dry it over silica gel for 5hours:the IRabsorption spectrum of a mineral oil dispersion of it exhibits maxima only at the same wavelengths as that of a similar preparation of USP Methylparaben RS.
B: Ignite about 0.3g,cool,and dissolve the residue in about 3mLof 3Nhydrochloric acid.Aplatinum wire dipped in this solution imparts an intense,persistent yellow color to a nonluminous flame.
pHá791ñ: between 9.5and 10.5,in a solution (1in 1000).
Water,Method Iá921ñ: not more than 5.0%.
Chloride á221ñ— A0.2-g portion shows no more chloride than corresponds to 0.10mLof 0.020Nhydrochloric acid (0.035%).
Sulfate á221ñ— A0.25-g portion shows no more sulfate than corresponds to 0.30mLof 0.020Nsulfuric acid (0.12%).
Assay— Gently reflux about 100mg of Methylparaben Sodium,accurately weighed,with 30mLof 1Nsodium hydroxide for 30minutes.Cool,add 25.0mLof potassium bromate solution (2.78in 500),5mLof potassium bromide solution (1in 8),and 10mLof hydrochloric acid,and immediately insert the stopper into the flask.Cool,shake for 15minutes,and allow to stand for 15minutes.Quickly add 15mLof potassium iodide TS,taking care to avoid the escape of bromine vapor,at once replace the stopper in the flask,and shake vigorously.Rinse the stopper and the neck of the flask with a small quantity of water,and titrate the liberated iodine with 0.1Nsodium thiosulfate VS,adding 3mLof starch TSas the endpoint is approached.[NOTE—About 15mLis needed.]Perform a blank determination (see Residual Titrationsunder Titrimetry á541ñ),and note the difference in volumes required.Each mLof the difference in volume of 0.1Nsodium thiosulfate is equivalent to 2.902mg of C8H7NaO3.
Auxiliary Information— Staff Liaison:Justin Lane,B.S.,Scientific Associate
Expert Committee:(EMC)Excipients:Monograph Content
USP28–NF23Page 3038
Phone Number:1-301-816-8323