[Code of Federal Regulations]
[Title 21, Volume 5]
[Revised as of April 1, 2004]
From the U.S. Government Printing Office via GPO Access
[CITE: 21CFR352.70]
[Page 297]
TITLE 21--FOOD AND DRUGS
CHAPTER I--FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN
SERVICES (CONTINUED)
PART 352_SUNSCREEN DRUG PRODUCTS FOR OVER-THE-COUNTER HUMAN USE
[STAYED INDEFINITELY]--Table of Contents
Subpart D_Testing Procedures
Sec. 352.70 Standard sunscreen.
(a) Laboratory validation. A standard sunscreen shall be used
concomitantly in the testing procedures for determining the SPF value of
a sunscreen drug product to ensure the uniform evaluation of sunscreen
drug products. The standard sunscreen shall be an 8-percent homosalate
preparation with a mean SPF value of 4.47 (standard deviation =1.279).
In order for the SPF determination of a test product to be considered
valid, the SPF of the standard sunscreen must fall within the standard
deviation range of the expected SPF (i.e., 4.47
1.279) and the 95-percent confidence interval for the mean SPF must
contain the value 4.
(b) Preparation of the standard homosalate sunscreen. (1) The
standard homosalate sunscreen is prepared from two different
preparations (preparation A and preparation B) with the following
compositions:
Composition of Preparation A and Preparation B of the Standard Sunscreen
------------------------------------------------------------------------
Ingredients------- Percent by weight
------------------------------------------------------------------------
Preparation A ............................
Lanolin................................. 5.00
Homosalate.............................. 8.00
White petrolatum........................ 2.50
Stearic acid............................ 4.00
Propylparaben........................... 0.05
Preparation B ............................
Methylparaben........................... 0.10
Edetate disodium........................ 0.05
Propylene glycol........................ 5.00
Triethanolamine......................... 1.00
Purified water U.S.P.................... 74.30
------------------------------------------------------------------------
(2) Preparation A and preparation B are heated separately to 77 to
82 [deg]C, with constant stirring, until the contents of each part are
solubilized. Add preparation A slowly to preparation B while stirring.
Continue stirring until the emulsion formed is cooled to room
temperature (15 to 30 [deg]C). Add sufficient purified water to obtain
100 grams of standard sunscreen preparation.
(c) Assay of the standard homosalate sunscreen. Assay the standard
homosalate sunscreen preparation by the following method to ensure
proper concentration:
(1) Preparation of the assay solvent. The solvent consists of 1
percent glacial acetic acid (V/V) in denatured ethanol. The denatured
ethanol should not contain a UV radiation absorbing denaturant.
(2) Preparation of a 1-percent solution of the standard homosalate
sunscreen preparation. Accurately weigh 1 gram of the standard
homosalate sunscreen preparation into a 100-milliliter volumetric flask.
Add 50 milliliters of the assay solvent. Heat on a steam bath and mix
well. Cool the solution to room temperature (15 to 30 [deg]C). Then
dilute the solution to volume with the assay solvent and mix well to
make a 1-percent solution.
(3) Preparation of the test solution (1:50 dilution of the 1-percent
solution). Filter a portion of the 1-percent solution through number 1
filter paper. Discard the first 10 to 15 milliliters of the filtrate.
Collect the next 20 milliliters of the filtrate (second collection). Add
1 milliliter of the second collection of the filtrate to a 50-milliliter
volumetric flask. Dilute this solution to volume with assay solvent and
mix well. This is the test solution (1:50 dilution of the 1-percent
solution).
(4) Spectrophotometric determination. The absorbance of the test
solution is measured in a suitable double beam spectrophotometer with
the assay solvent and reference beam at a wavelength near 306
nanometers.
(5) Calculation of the concentration of homosalate. The
concentration of homosalate is determined by the following formula which
takes into consideration the absorbance of the sample of the test
solution, the dilution of the 1-percent solution (1:50), the weight of
the sample of the standard homosalate sunscreen preparation (1 gram),
and the standard absorbance value (172) of homosalate as determined by
averaging the absorbance of a large number of batches of raw homosalate:
Concentration of homosalate =absorbance x 50 x 100 x 172 =percent
concentration by weight.
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