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C12H18O2 194.27

4-Hexylresorcinol [136-77-6].
»Hexylresorcinol,dried over silica gel for 4hours,contains not less than 98.0percent and not more than 100.5percent of C12H18O2.
[Caution—Hexylresorcinol is irritating to the oral mucosa and respiratory tract and to the skin,and its solution in alcohol has vesicant properties. ]
Packaging and storage— Preserve in tight,light-resistant containers.
A: To 1mLof a saturated solution of it add 1mLof nitric acid:a light red color appears.
B: To 1mLof a saturated solution of it add 1mLof bromine TS:a yellow,flocculent precipitate is formed.Add 2mLof 6Nammonium hydroxide:the precipitate dissolves,producing a yellow solution.
Melting range,Class Iá741ñ: between 62and 67.
Acidity— Dissolve 250mg in 500mLof water,add methyl red TS,and titrate with 0.020Nsodium hydroxide:no more than 1.0mLis required for neutralization.
Residue on ignition á281ñ: not more than 0.1%.
Mercury— [NOTE—Select all reagents for this test to have as low a content of mercury as practicable,and store all reagent solutions in containers of borosilicate glass.Glassware used in this test shall be specially cleaned by being soaked in warm 8Nnitric acid for 30minutes and rinsed with water.Keep flasks for this determination separate from other flasks,and use only for mercury determinations.]
Standard preparation— Transfer 34.0mg of mercuric chloride to a 250-mLvolumetric flask.Add 1drop of hydrochloric acid,add water to dissolve,and dilute with water to volume.Transfer 1.0mLof this solution to a 100-mLvolumetric flask,add 1drop of hydrochloric acid,and dilute with water to volume.Transfer 1.0mLof this solution to a 500-mLvolumetric flask,add 1drop of hydrochloric acid,and dilute with water to volume.
Test preparation— Transfer 134mg to a 250-mLbeaker,and cautiously add 10mLof 11Nnitric acid and 10mLof 18Nsulfuric acid.Digest,with the aid of heat,in a well-ventilated hood until the evolution of brown fumes ceases.Cautiously add an additional 10mLof 11Nnitric acid,and continue heating until no more fumes are evolved.Cool,transfer to a 200-mLvolumetric flask,and dilute with water to volume.
Procedure— Transfer 100mLof Standard preparationto a 300-mLmercury analysis reaction vessel,add 2drops of potassium permanganate solution (1in 20),and mix (the solution should be purple;add additional permanganate solution dropwise,if necessary).Add 5mLof 11Nnitric acid,stir,and allow to stand for not less than 15seconds.Add 5mLof 18Nsulfuric acid,stir,and allow to stand for not less than 45seconds.Add 5mLof hydroxylamine hydrochloride solution (3in 200),stir,and allow to stand until the solution turns light yellow or colorless.Add 5mLof stannous chloride solution (1in 10)[NOTE—Disregard the presence of insoluble matter in this solution;mix prior to use],immediately insert the aerator connected to the air pump,and determine the maximum absorbance of the treated Standard preparationat the mercury resonance line of 253.65nm,with a suitable atomic absorption spectrophotometer equipped with a mercury hallow-cathode lamp and an absorption cell that permits the flameless detection of mercury.Connect in a closed system with a circulating air pump,a calcium chloride drying tube,and an aerator inserted in a 300-mLreaction vessel so that air passed through the treated preparation contained in the reaction vessel evaporates any metallic mercury present.In a similar manner,treat 100mLof the Test preparationand 100mLof water (reagent blank),and determine the maximum absorbances at the same wavelength [NOTE—Check the zero setting of the instrument frequently].The absorbance of the solution from the Test preparationdoes not exceed that of the solution from the Standard preparation(3ppm).
Resorcinol and other phenols— Shake about 1g with 50mLof water for a few minutes,filter,and to the filtrate add 3drops of ferric chloride TS:no red or blue color is produced.
Assay— Dissolve 70mg to 100mg of Hexylresorcinol,previously dried over silica gel for 4hours and accurately weighed,in 10mLof methanol in a 250-mLiodine flask.Add 30.0mLof 0.1Nbromine VS,then add quickly 5mLof hydrochloric acid,and insert the stopper in the flask immediately.Cool the flask under running water to room temperature,shake vigorously for 5minutes,then set aside for 5minutes.Add 6mLof potassium iodide TSaround the stopper,cautiously loosen the stopper,again insert the stopper tightly,and swirl gently.Add 1mLof chloroform,and titrate the liberated iodine with 0.1Nsodium thiosulfate VS,adding 3mLof starch TSas the endpoint is approached.Perform a blank determination (see Residual Titrationsunder Titrimetry á541ñ).Each mLof 0.1Nbromine is equivalent to 4.857mg of C12H18O2.
Auxiliary Information— Staff Liaison:Behnam Davani,Ph.D.,MBA,Senior Scientist
Expert Committee:(PA7)Pharmaceutical Analysis 7
USP28–NF23Page 945
Phone Number:1-301-816-8394