501SALTS OF ORGANIC NITROGENOUS BASES, chemical structure, molecular formula, Reference Standards

á501ñSALTS OF ORGANIC NITROGENOUS BASES

Standard Preparation— Unless otherwise directed,prepare a solution in dilute sulfuric acid (1in 70)containing,in each mL,about 500µg of the specified USP Reference Standard,calculated on the anhydrous basis,and accurately weighed.

Assay Preparation— If the dosage form is a tablet,weigh and finely powder not less than 20tablets,weigh accurately a portion of the powder,equivalent to about 25mg of the active ingredient,and transfer to a 125-mLseparator;or,if the dosage form is a liquid,transfer a volume of it,equivalent to about 25mg of the active ingredient and accurately measured,to a 125-mLseparator.Then to the separator add 20mLof dilute sulfuric acid (1in 350),and shake vigorously for 5minutes.Add 20mLof ether,shake carefully,and filter the acid phase into a second 125-mLseparator.Shake the ether phase with two 10-mLportions of dilute sulfuric acid (1in 350),filter each portion of acid into the second separator,and discard the ether.To the acid extract add 10mLof sodium hydroxide TSand 50mLof ether,shake carefully,and transfer the aqueous phase to a third 125-mLseparator containing 50mLof ether.Shake the third separator carefully,and discard the aqueous phase.Wash the two ether solutions,in succession,with a single 20-mLportion of water,and discard the water.Extract each of the two ether solutions with 20-,20-,and 5-mLportions of dilute sulfuric acid (1in 70),in the order listed,but each time extract first the ether solution in the third separator and then that in the second separator.Combine the acid extracts in a 50-mLvolumetric flask,dilute with the acid to volume,and mix.

NOTE—Hexane or heptane may be substituted for ether if the distribution ratio of the nitrogenous base between water and hexane,or between water and heptane,favors complete extraction by the organic phase.

Procedure— Unless otherwise directed,dilute 5.0mLeach of the Standard Preparationand the Assay Preparationwith dilute sulfuric acid (1in 70)to 100.0mL,and determine the absorbance of each solution at the specified wavelength,using dilute sulfuric acid (1in 70)as the blank.Designate the absorbance of the solution from the Standard Preparationas ASand that from the Assay Preparationas AU,and calculate the result of the assay as directed in the individual monograph.