FR2710151A1 - Apparatus and method for in vitro determination of the protection factor and water resistance of a cosmetic product of the sunscreen type - Google Patents

Abstract

The present invention relates to the in vitro determination of the sun protection factor of a cosmetic product of the sunscreen type. The apparatus comprises a light source (1), a working bundle (2), a monochromator (3), a measurement cell (4), a physical receiver (5) of the monochromated beam modified by the cell, and a measurement means (8) receiving the signal delivered by the receiver (5). According to the invention, the measurement cell consists of a solid plate, for example of quartz, onto which a deposit matrix of the product to be tested adheres.

Description

APPARATUS AND METHOD FOR DETERMINING IN VITRO
COEFFICIENT OF PROTECTION AND RESISTANCE TO WATER
A COSMETIC PRODUCT OF THE SUNSCREEN TYPE
The present invention relates to the field of cosmetics, and more particularly that of cosmetic products of the sunscreen type for topical use, whatever the form or presentation of these.

 Within the meaning of the present invention, by cosmetic product, it will be understood both a composition or formulation of different ingredients or active ingredients with a suitable carrier or excipient, regardless of the physical form of this formulation or composition, such as emulsion, cream , lotion, etc ...., a compound or particular active ingredient, which is sought specific effectiveness in terms of sun protection.

In accordance with the following documents
J. Soc. Cosmet. Chem, 40, 127-133 (May / June 1989), BL DIFFEY and J. ROBSON
Cosmetics and Toiletries Vol.107, October 1992, pages 119-123, Richard L Sellers and Franklin G Carpenter, there has already been described an apparatus, of the spectrophotometer type, for determining or approximating in vitro the sun protection coefficient of a cosmetic product of the sunscreen type, comprising (a) at least one light source, such as a lamp
arc in xenon atmosphere, to emit a beam
luminous working, whose spectral range covers
at least the spectra WA and WB, starting at
a low value (Xb) of at least 170 nm, and
terminating at a high value (xh) at 400 nm (b) a monochromator of the working light beam,
comprising one or more networks, allowing
isolate or separate in the work beam, a
plurality of quasi-monochromatic radiations or
distinct spectral bands; it is understood that everything
other monochromator may be suitable, such as one or
several dispersive elements, or one or more
interferential filters (c) a measuring cell intercepting the beam
bright working, arranged between the monochromator
and the physical receiver described hereinafter; this
cell comprises, on the one hand, a rigid support and
plane, arranged perpendicular to the beam axis
bright working, and having an opening
circular for the passage or transmission of this
last, and on the other hand, a deposit matrix, in one
flexible material and at least partly transparent
vis-à-vis the WA and UV-B, mounted on the support
rigid by closing and through the opening
aforementioned circular; this montage consists of sticking the
deposit matrix on a photographic film
relatively rigid, itself fixed on the support, in
closing and through its circular opening;
the outer face of the deposit matrix is irregular
or porous as to its surface, and is suitable for the
receiving a layer of the cosmetic product to
test ; preferentially the flexible material of the
deposit matrix is an adhesive film, such as
marketed by the Company 3M Company, (St Paul,
Minnesota, USA), under the name "Transpore"; he
is understood that the measuring cell previously
described, can be arranged, totally
equivalent to that described above, between
light source and the monochromator (d) at least one physical receiver, for example a
photo-multiplier, working light beam
monochromate, having been modified by its
through the rigid support of the cell and the
deposit matrix, with or without the product layer
cosmetic to be tested, to deliver a signal
electric proportional to the energy flow received; (e) a measuring device receiving, directly or
indirectly (eg after amplification), the
electrical signal delivered by the physical receiver,
comprising calculating means, of the type
microprocessor in relation with a RAM and
a read-only memory, allowing to compute
successively
- the monochromatic PFA protection factor for
each radiation isolated by the monochromator,
from the two electrical signals delivered with the
measuring cell respectively without and with
layer of the cosmetic product to be tested
- and the result of the following formula

in which
* CP represents the sun protection factor
cosmetic product tested
* It is the spectral irradiance of the solar light
natural, for sunstroke conditions
predetermined or chosen, in particular
according to the terrestrial latitude of insolation
* A is the relative efficiency of a radiation
monochromatic of natural sunlight,
to induce erythema on human skin.

With regard to spectral irradiance, preferentially one will choose the one whose values have been published by the following authors, for a latitude of 400 north, an insolation angle relative to the zenith of 200, and an ozone layer of thickness 0.305 cm - P Bener, Final Technical Report DA / JA37-68 C-1017,
European Research Office, US Army, London (1972) - SAW Gerstl, A. Zardecki, and HL Wiser, WB Handbook,
Vol.l, Report LA-UR-83-728, Los Alamos National
Laboratory (1983).

With regard to the relative efficiency of monochromatic radiations, reference is made to the numerical values already given in the following publication, namely:
AF McKinlay BL Diffey, CIE Journal 6, 17-22 (1987).

In general, the apparatus described above makes it possible to implement the following method for determining in vitro the sun protection coefficient of a cosmetic product of the sunscreen type, according to which
(A) A light beam is produced and emitted
work, whose useful spectral range starts at
a low value (sb) of at least 170 nm, and
ends at a high value (sh) at least equal to
400 nm, and covering at least the WA and WB spectra.

(B) Isolating in the work beam a plurality
monochromatic radiation or bands
spectral.

(C) We intercalate in the working light beam,
and perpendicular to its axis, a matrix of
deposit, in a flexible material and at least in
transparent portion vis-à-vis the WA and WB, and
of which one of the irregular faces is adapted to
receive a layer of the cosmetic product to
test.

(D) Convert the working light beam,
monochromate according to (B), modified by its
through the deposit matrix, with or without the
layer of the cosmetic product to be tested, in one
proportional electric signal.

(E) We transform the electrical signal into a value
of measurement, at the end of the following steps
- determination of the protection factor
monochromatic (PFx), for each radiation
isolated according to (B), from the signals
obtained respectively without and
with the layer of the cosmetic product to
test ;
- determination of the result of the formula
next

in which
* CP represents the coefficient of protection
solar cosmetic product tested
* Ex is the spectral irradiance of light
solar energy, for conditions
of predetermined insolation is is the relative efficiency of a radiation
monochromatic solar light
natural, to induce erythema on the
human skin.

For more details on the apparatus and the method defined generally and previously, reference will be made to the first two publications cited in the present description, respectively from MM. Diffey and Robson, and
Messrs. Sellers and Carpenter, the content of which is incorporated in this description as needed.

 Today, the apparatus and method described above do not make it possible to determine sun protection coefficients with very liquid products or products containing a majority of water-soluble constituents; in this case, the results obtained are much lower than those found in vivo.

 Said apparatus and method also do not make it possible to give an objective measure of the protection coefficient, when the latter is high and in particular greater than 15, the results obtained being much higher than those found in vivo.

 In addition, they do not make it possible to carry out water resistance tests of products or sunscreens, so that they must be made in vivo. As is known, in vivo measurements in this field do not give reproducible results from one laboratory to another, and to have a statistically significant value, measurements must be made with a sample of at least 20 people.

 In addition, the values obtained depend on the type of skin, the exposure lamp used, and how the expert will appreciate the results.

 It is therefore an object of the present invention to modify the apparatus and the method defined above, in order to make it possible to carry out protection coefficient determination tests, whatever the cosmetic product tested, and to carry out in vitro resistance tests. the water.

 According to the present invention, the support of the measuring cell comprises at least one solid blade, that is to say for example without central opening, removable, a material at least partially transparent vis-à-vis the WA and WB, on which adheres or is glued the deposition matrix.

 Preferably, the material of the solid blade is a quartz. And as before, the material of the deposition matrix may be a simple tape or adhesive patch, material marketed under the name "Transpore", and identified above. It can therefore be a polymer, in particular a natural polymer.

 The solution according to the present invention further provides the following advantages.

 It makes it possible to test products in solution, for example in alcoholic solution, where the measuring cell according to the solution prior to the invention did not allow such tests, particularly in view of the deformation of the deposition matrix, by impregnation with the solvent. In other words, the solution according to the invention makes it possible to free the apparatus and the method described above, with respect to the physical or physico-chemical form of the tested product, and in a way to make them "universal".

 According to the invention, the rigid support carried by the solid blade, for example made of quartz, allows a better distribution, on the outer face of the deposition matrix, of the cosmetic product to be tested, since the application of the latter is carried out without deformation, formerly due to the existence of a circular opening, the sheet used as a matrix.

The present invention is now described with reference to the accompanying drawing, in which - Figure 1 schematically represents a
apparatus according to the invention, with a single and unique
work beam - Figure 2 schematically shows a
apparatus according to the invention, with a double beam, one of
reference and the other working.

According to FIG. 1, the apparatus according to the invention generally comprises (a) one or more light sources 1, to emit a
2 work light beam, whose domain
spectral spectrum, whether continuous or discontinuous, starts at a
low value xbl at least equal to 170 nm, and ends
at a high value Ah at 400 nm, thus covering the
minus the spectra WA and WB (b) a monochromator 3 of the working light beam,
traditional, allowing to isolate in the beam 2,
a plurality of monochromatic radiations; (c) a measuring cell 4 intercepting the beam
bright working, arranged either between source 1
and the monochromator 3 (cf representation in lines
solid) or between the monochromator and the receiver
described below (cf representation in
dotted lines according to FIG. 1) (d) at least one physical receiver 5 of the light beam
monochromatic work, modified by its transition to
through the rigid support of the measuring cell,
to deliver an electrical signal 10 proportional to the
light energy flux received (e) a measuring means 8 receiving, directly or
indirectly, the electrical signal 10, and allowing
to successively calculate the factor of
PFx protection, and finally the coefficient of
sun protection, according to the formula and
information given previously.

 According to the present invention, the measuring cell comprises, on the one hand, as a rigid and plane support, a solid plate 6, for example made of quartz, and therefore transparent to WA and WB, arranged perpendicular to the axis of the beam 2, and secondly a deposit matrix 7, made of a relatively thin and flexible material, at least partially transparent with respect to WA and WB, adhering or sticking on the blade 6. This is the face external, relatively irregular surface or porous, which receives a layer 8 of the cosmetic product to be tested, in a controlled or predetermined surface concentration.

 FIG. 2 represents the optical and electrical diagram of an apparatus according to the invention, with double light beam, namely working or measurement, and reference beam.

Preferably, the deposition matrix has the following technical characteristics - it comprises a support, chosen from the materials
following, ie, or a nonwoven, preferentially
of rayon fibers with an acrylic resin, or a
extruded microperforated film, preferentially
polyethylene - with on one side, an adhesive, preferably a
copolymer of an acrylate, optionally with a
Accelerator adhesion - the support having a thickness of the order of
a few hundred microns, with pores or
passages of the order of 50 to 100 microns.

With the device identified previously, the tests are carried out according to the same protocols as those described in the following reference
J. Soc. Cosmet. Chem, 40, 127-133 (May / June 1989), BL DIFFEY and J. ROBSON.

 The following tests are now described by way of example.

A spectrophotometer "WIKON 930" from the company KONTRON INSTRUMENTS, a full quartz blade for the measuring cell W, a "Transpore" band from the
Company 3M Company, St Paul, Minnesota / USA, as deposit matrix, precision balance and microcomputer for easy calculations.

 A first absorption measurement W is performed using the spectrophotometer.

 Then, the cosmetic product to be studied is weighed by depositing it directly on the deposition matrix. The amount used is 1.5 mg / cm 2 if working in DIN, or 2 mg / cm 2 in FDA. The cream is distributed over the entire surface of the deposit matrix in small piles. Then, it is spread with a fingerstall in a uniform way. Once the product is well distributed on the surface, a second spectrophotometric measurement is performed.

 The operation is repeated three times as a whole, so as to obtain three measurements without product, and three measurements with product.

 The protection factor (PFx) and the sun protection factor (CP) are calculated as indicated above.

The values of the spectral irradiance Ex used in the present case, were chosen to represent the solar light received in the south of Europe (400 of northern latitude), in the middle of the summer, when the sun is at the zenith . For the relative erythematous efficiency x, the values given by the Commission were used
International Lighting.

Numerical values are given in the table below

<tb> Length <SEP> wave <SEP> EA <SEP> EA <SEP> Ex
<tb><SEP> (nm) <SEP> W / (m2 * nm) <SEP> (CIE <SEP> 1987)
<tb><SEP> 290 <SEP> 3.68 * 10-6 <SEP> 1.0
<tb><SEP> 295 <SEP> 7.97 * 10-4 <SEP> 1.0
<tb><SEP> 300 <SEP> 1.28 * 10-2 <SEP> 0.65
<tb><SEP> 305 <SEP> 6.51 * 10-2 <SEP> 0.22
<tb><SEP> 310 <SEP> 0.171 <SEP> 7.4 * 10-2 <SEP>
<tb><SEP> 315 <SEP> 0.295 <SEP> 2.5 * 10-2
<tb><SEP> 320 <SEP> 0.398 <SEP> 8.6 * 10-3
<tb><SEP> 325 <SEP> 0.536 <SEP> 2.9 * 10-3
<tb><SEP> 330 <SEP> 0.630 <SEP> 1.4 * 10-3
<tb><SEP> 335 <SEP> 0.65 <SEP> 1.2 * 10-3
<tb><SEP> 340 <SEP> 0.68 <SEP> 9.7 * 10-4
<tb><SEP> 345 <SEP> 0.69 <SEP> 8.1 * 10-4
<tb><SEP> 350 <SEP> 0.70 <SEP> 6.8 * 10-4
<tb><SEP> 355 <SEP> 0.71 <SEP> 5.7 * 10-4
<tb><SEP> 360 <SEP> 0.73 <SEP> 4.8 * 10-4
<tb><SEP> 365 <SEP> 0.75 <SEP> 4.0 * 10-4
<tb><SEP> 370 <SEP> 0.78 <SEP> 3.4 * 10-4
<tb><SEP> 375 <SEP> 0.80 <SEP> 2.9 * 10-4
<tb><SEP> 380 <SEP> 0.83 <SEP> 2.4 * 10-4
<tb><SEP> 385 <SEP> 0.86 <SEP> 2.0 * 10-4
<tb><SEP> 390 <SEP> 0.90 <SEP> 1.7 * 10-4
<tb><SEP> 395 <SEP> 0.93 <SEP> 1.4 * 10-4
<tb><SEP> 400 <SEP> 0.97 <SEP> 1.2 * 10-4
<Tb>
We tested a series of solar products bought at random in the trade. The results show a good correlation between the values found according to the invention, and the protection coefficients displayed by the manufacturers.

 The solution according to the invention is particularly essential when the products studied contain water-soluble filters, when the protection coefficients are high, that is to say greater than 15, or when the products are very liquid.

Results

<tb><SEP> Coefficient <SEP> Coefficient <SEP> of
<tb> MANUFACTURER <SEP> of <SEP> protection <SEP> protection <SEP> found
<tb><SEP> announced
<tb><SEP> WB <SEP> UV-A
<tb><SEP> B2 <SEP> 2 <SEP> 1 <SEP> 3.47 <SEP> 2.05
<tb><SEP> B4 <SEP> 4 <SEP> 5.56 <SEQ> 2.87
<tb><SEP> B8 <SEP> 8 <SEP> 7.58 <SEP> 3.07
<tb><SEP> I8 <SEP> 8 <SEP> 8.67 <SEP> 2.93
<tb><SEP> I25 <SEP> 25 <SEP> 27.0 <SEP> 7.45
<tb><SEP> A79 <SEP> 7 <IP <9 <SEP> 6.88 <SEP> 2.08
<tb><SEP> A15 <SEP>IP> 15 <SEP> 18.91 <SEP> 8.83
<tb><SEP> M6 <SEP> 6 <SEP> 7.41 <SEP> 2.25
<tb><SEP> 020 <SEP> 20 <SEP> 16.38 <SEP> 6.56
<tb><SEP> R9G <SEP> 6 <SEP> 7.52 <SEP> X <SEP><SEP> 3.32
<Tb>
The products were tested at 1.5 mg / cm 2 (DIN method).

 A method for testing the water resistance of solar products was then used, from the method previously described. This method of "screening" is much simpler, allows to have in a few hours, a predictive result; This avoids going "blindly" and incurring expenses for products whose effectiveness is uncertain.

 It suffices to repeat the protocol described above. Once the first measurement is made, the quartz slide 6 with the deposition matrix 7 is immersed in a beaker filled with running water and measurements are made every ten minutes, which makes it possible not only to check the resistance to the reaction. water tested products, but also to have a much finer appreciation of the phenomenon, by studying the kinetics of the evolution of the sun protection coefficient.

 For known products, and already tested in vivo, it is found that the results obtained with the method according to the invention are in agreement with those already published or communicated by the manufacturers.

Claims (4)

 1) Apparatus for determining in vitro the sun protection coefficient of a cosmetic product of the sunscreen type, comprising (a) at least one light source (1), to emit a  light beam (2,21) working, whose domain  spectral value starts at a low value (xb) at  less equal to 170 nm, and ends at a high value  (Xh) at least 400 nm, and covering at least  spectra W-A and W-B (b) a monochromator (3) of the working light beam,  including a dispersive element or a  network, or a series of interferential filters, for  isolate in the work beam a plurality of  quasi-monochromatic radiations or bands  (c) a measuring cell (4) intercepting the beam  bright working, arranged between the source  light and the monochromator, or between the latter and  the physical receiver below (5) (d), said cell  measuring device comprising, on the one hand, a rigid support (6)  and plane, arranged perpendicular to the axis of  beam (2) bright working, and arranged for  forward it, and secondly a  matrix (7) for depositing, in a relatively  thin and flexible and at least partially transparent  vis-à-vis UV-A and UV-B, mounted on the support  rigid, and whose outer face is adapted to receive  a layer (8) of the cosmetic product to be tested; (d) at least one physical receiver (5), in particular a  photo-multiplier of the working light beam  monochromate, modified by its passage through the  rigid support of the cell and the matrix of  deposit, with or without the layer of the cosmetic product to  test, to deliver an electrical signal (10)  proportional to the energy flow received (e) measurement means (8) receiving, directly or  indirectly the electrical signal (7), comprising  calculation means successively  - the monochromatic protection factor (PFx) for  each radiation isolated by the monochromator (3),  from the two electrical signals delivered  with the measuring cell, respectively without and  with the layer of the cosmetic product to be tested  - the result of the following formula

 for inducing erythema on human skin characterized in that the support (6) of the measuring cell comprises at least one removable solid blade of a material at least partially transparent to WA and UV-B, on which the matrix (7) of deposit adheres.  monochromatic of natural sunlight,  * EA is the relative efficiency of a radiation  predetermined insolation  solar energy, for conditions  * Ex is the spectral irradiance of light  solar cosmetic product tested  * CP represents the coefficient of protection  in which  2) Apparatus according to claim 1, characterized in that the material of the blade (6) solid and removable is a quartz.  3) Apparatus according to claim 1, characterized in that the material of the matrix (7) deposition is a polymer, including natural.  4) Process for determining in vitro the sun protection coefficient of a cosmetic product of the sunscreen type, according to which (A) is produced (1) and emits a light beam (2,21) of  work, whose useful spectral range begins at a  low value (xb) at least equal to 170 nm, and  ends at a high value (xh) of at least 400  nm, and covering at least the W-A and W-B spectra.  monochromatic radiations or spectral bands. (B) Isolating (3) in the work beam a plurality  cosmetic to test.  faces is adapted to receive a layer of the product  transparent to the W-A and W-B, and one of which  deposit, in a flexible material and at least in part  and perpendicular to its axis, a matrix (7) of (C) is interleaved (4) in the working light beam,  proportional electric.  cosmetic product to be tested, in one signal (10)  through the deposition matrix, and / or the layer of  monochromate according to (B), modified by its (D) Converting (5) the working light beam,

 - determination of the result of the following formula  cosmetic to test  respectively without and with the layer of the product  according to (B), from the electrical signals obtained  monochromatic (PFx), for each isolated radiation  - determination of the protection factor  of measurement, at the end of the following steps (E) transform (8) the electrical signal into a value  for inducing erythema on human skin, characterized in that the matrix (7) is deposited on a slide (6) filled with a material at least partially transparent to UV-A and UV-radiation. B.  monochromatic of natural sunlight,  * A is the relative efficiency of a radiation  predetermined  natural, for sunstroke conditions  * Ex is the spectral irradiance of sunlight  cosmetic product tested  * CP represents the sun protection factor  in which