Tolcapone
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C14H11NO5 273.24

Methanone, (3,4-dihydroxy-5-nitrophenyl)(4-methylphenyl)-.
3,4-Dihydroxy-4¢-methyl-5-nitrobenzophenone [134308-13-7].
» Tolcapone contains not less than 98.5 percent and not more than 101.5 percent of C14H11NO5, calculated on the anhydrous and solvent-free basis.
Packaging and storage— Preserve in tight, light-resistant containers, and store between 20 and 25.
Identification—
B: The retention time of the major peak in the chromatogram of the Assay preparation corresponds to that in the chromatogram of the Standard preparation, as obtained in the Assay.
Absorptivity—
Diluent— Dilute 100 mL of 1 N hydrochloric acid with dehydrated alcohol to 1000 mL.
Test preparation— Prepare a solution of Tolcapone having a concentration of 0.01 mg per mL in Diluent.
Procedure— Proceed as directed under Spectrophotometry and Light-Scattering 851, and measure the absorbance: the maximum is between 265.2 and 269.3, and the absorptivity is between 75.29 and 79.93.
Water, Method I 921: not more than 0.1%.
Residue on ignition 281: not more than 0.1%.
Related compounds—
test 1—
Adsorbent: 0.25-mm layer of chromatographic silica gel mixture with a suitable fluorescing substance (see Chromatography 621).
Standard solution 1— Dissolve an accurately weighed portion of USP Tolcapone RS in chloroform, and dilute quantitatively, and stepwise if necessary, with chloroform to obtain a solution having a known concentration of 0.4 mg per mL.
Standard solution 2— Transfer 2.0 mL of Standard solution 1 to a 10-mL volumetric flask, dilute with chloroform to volume, and mix.
Standard solution 3— Transfer 1.0 mL of Standard solution 1 to a 10-mL volumetric flask, dilute with chloroform to volume, and mix.
Standard solution 4— Transfer 5.0 mL of Standard solution 3 to a 10-mL volumetric flask, dilute with chloroform to volume, and mix.
Test solution— Transfer about 200 mg of Tolcapone, accurately weighed, to a 5-mL volumetric flask, dissolve in and dilute with chloroform to volume, and mix. [note—Prepare this solution last and chromatograph immediately.]
Application volume: 10 µL.
Developing solvent system: a mixture of chloroform, anhydrous formic acid, and ethyl acetate (83:15:2).
Procedure— Apply the Test solution and each of the Standard solutions as directed for Thin-Layer Chromatography under Chromatography 621 at about 4 cm from the lower edge of the plate. Dry the plate in a current of cold air, and view it under short-wavelength UV light. The RF values of analytes are as follows.
Compound RF
Tolcapone related compound A about 0.2
Tolcapone about 0.5
Tolcapone related compound B about 0.7
Compare any spot at RF of 0.0 in the chromatogram obtained from the Test solution with the principal spot of Standard solution 2, Standard solution 3, and Standard solution 4, and obtain the approximate amount: not more than 0.1% of any impurity at RF of 0.0 is found. [note—The RF of tolcapone related compound A and tolcapone related compound B are given just for reference. They are quantified in Test 2.]
test 2—
Diluent, System suitability solution, Mobile phase, and Chromatographic system— Proceed as directed in the Assay.
Standard solution— Use the Standard preparation, prepared as directed in the Assay.
Test solution— Use the Assay preparation.
Procedure— Separately inject equal volumes (about 20 µL) of the Standard solution and the Test solution into the chromatograph, record the chromatograms, and measure the peak areas. Calculate the percentage of each impurity in the portion of Tolcapone taken by the formula:
(50,000F)(C/W)(ri / rS)
in which C is the concentration, in mg per mL, of USP Tolcapone RS in the Standard solution; F is the relative response factor of the impurity according to the table below; W is the weight, in mg, of Tolcapone, calculated on the solvent- and water-free basis, used to prepare the Test solution; ri is the peak area for any impurity in the Test solution; and rS is the peak area for tolcapone in the Standard solution: the impurities meet the requirements given in the table below.
Compound Name Relative
Retention
Time
Relative
Response
Factor
Limit (%)
Tolcapone related compound A about 0.6 1.14 0.1
Tolcapone 1.0
Tolcapone related compound B 1.36 0.98 0.2
Unknown impurities 1.0 0.1 individual,
0.2 total unknown
Total impurities 0.5
Assay—
Diluent— Prepare a mixture of methanol and acetonitrile (24:15).
System suitability solution— Dissolve an accurately weighed quantity of USP Tolcapone Related Compound A RS, USP Tolcapone RS, and USP Tolcapone Related Compound B RS in Diluent; and dilute quantitatively, and stepwise if necessary, with Diluent to obtain a solution having a known concentration of about 5 µg per mL, 5 µg per mL, and 10 µg per mL, respectively. Transfer 2.0 mL of this solution to a 100-mL volumetric flask, add about 63 mL of Diluent, dilute with water to volume, and mix.
Mobile phase— Prepare a filtered and degassed mixture of methanol, 0.05 M monobasic potassium phosphate having a pH of 2.0 ± 0.1, and acetonitrile (8:7:5). Make adjustments if necessary (see System Suitability under Chromatography 621).
Standard preparation— Dissolve an accurately weighed quantity of USP Tolcapone RS in Diluent; and dilute quantitatively, and stepwise if necessary, with Diluent to obtain a solution having a known concentration of about 1.0 mg per mL. Transfer 5.0 mL of this solution to a 50-mL volumetric flask, add about 27.5 mL of Diluent, dilute with water to volume, and mix.
Assay preparation— Transfer about 50 mg of Tolcapone, accurately weighed, to a 50-mL volumetric flask, dissolve in and dilute with Diluent to volume, and mix. Transfer 5.0 mL of this solution to a 50-mL volumetric flask, add about 27.5 mL of Diluent, dilute with water to volume, and mix.
Chromatographic system (see Chromatography 621)— The liquid chromatograph is equipped with a 230-nm detector and a 4.0-mm × 25-cm column that contains packing L1. The flow rate is about 1 mL per minute. Chromatograph the System suitability solution, and record the peak responses as directed for Procedure: the relative retention times are about 0.6 for tolcapone related compound A, 1.0 for tolcapone, and about 1.4 for tolcapone related compound B; and the resolution, R, between tolcapone related compound B and tolcapone is not less than 4.0. Chromatograph the Standard preparation, and record the peak responses as directed for Procedure: the relative standard deviation for replicate injections is not more than 1.0%.
Procedure— Separately inject equal volumes (about 20 µL) of the Standard preparation and the Assay preparation into the chromatograph, record the chromatograms, and measure the areas for the major tolcapone peaks. Calculate the quantity, in mg, of C14H11NO5 in the portion of Tolcapone taken by the formula:
500C(rU / rS)
in which C is the concentration, in mg per mL, of USP Tolcapone RS in the Standard preparation; and rU and rS are the peak responses obtained from the Assay preparation and the Standard preparation, respectively.
Auxiliary Information— Please check for your question in the FAQs before contacting USP.
Topic/Question Contact Expert Committee
Monograph Ravi Ravichandran, Ph.D.
Senior Scientist
1-301-816-8330
(MDPP05) Monograph Development-Psychiatrics and Psychoactives
Reference Standards Lili Wang, Technical Services Scientist
1-301-816-8129
RSTech@usp.org
USP32–NF27 Page 3768
Pharmacopeial Forum: Volume No. 30(6) Page 2051
Chromatographic Column—
Chromatographic columns text is not derived from, and not part of, USP 32 or NF 27.