Sulisobenzone
308.31Benzenesulfonic acid, 5-benzoyl-4-hydroxy-2-methoxy-.
5-Benzoyl-4-hydroxy-2-methoxybenzenesulfonic acid
[4065-45-6].» Sulisobenzone contains not less than 97.0 percent and not more than 103.0 percent of C14H12O6S, calculated on the anhydrous basis.
Packaging and storage—
Preserve in tight, light-resistant containers.
Identification, Ultraviolet Absorption 
197U
—
197U—
Solution:
10 µg per mL.
Medium:
water.
Absorptivities, calculated on the anhydrous basis, do not differ by more than 3.0%.
Water, Method I 921:
not more than 2.0%.
921:
not more than 2.0%.
Assay—
Accurately weigh about 0.25 g of Sulisobenzone, and dissolve in 5 mL of water in a conical flask. Add 50 mL of dehydrated isopropyl alcohol, titrate with 0.1 N tetrabutylammonium hydroxide VS, and determine the two endpoints potentiometrically. V1 and V2 are the volumes, in mL, of titrant needed to reach the first and second endpoints, respectively. To determine the blank value caused by tertiary amines present as impurities in the titrant, dissolve V1/5 mL of 0.5 N hydrochloric acid VS in 50 mL of dehydrated isopropyl alcohol, and subsequently add (5 
V1/5) mL of water. Titrate with 0.1 N tetrabutylammonium hydroxide VS, and determine the two endpoints potentiometrically. V1B and V2B are the volumes, in mL, of titrant needed to reach the first and second endpoints, respectively. The blank value VBV , in mL, is obtained by the formula:
V1/5) mL of water. Titrate with 0.1 N tetrabutylammonium hydroxide VS, and determine the two endpoints potentiometrically. V1B and V2B are the volumes, in mL, of titrant needed to reach the first and second endpoints, respectively. The blank value VBV , in mL, is obtained by the formula:
V2B V1B
Calculate the percentage of C14H12O6S in the portion of Sulisobenzone taken by the formula:
V1B
308.31C[2V1 (V2 VBV)](1/W)(0.001)100
in which 308.31 is the molecular weight of Sulisobenzone; C is the concentration, in moles per L, of the 0.1 N tetrabutylammonium hydroxide VS; W is the weight, in g, of Sulisobenzone taken; 0.001 is the conversion factor for converting mL to L; and 100 is the conversion factor to percentage.
(V2 VBV)](1/W)(0.001)100
Auxiliary Information—
Please check for your question in the FAQs before contacting USP.
| Topic/Question | Contact | Expert Committee |
| Monograph | Feiwen Mao, M.S.
Scientist 1-301-816-8320 |
(MDOOD05) Monograph Development-Ophthalmics Oncologics and Dermatologicals |
| Reference Standards | Lili Wang, Technical Services Scientist 1-301-816-8129 RSTech@usp.org |
USP32–NF27 Page 3639
Pharmacopeial Forum: Volume No. 33(3) Page 456