prEN ISO 24443

Determination of sunscreen UVA photoprotection in vitro (ISO/DIS 24443:2020)

In vitro Bestimmung des UVA-Schutzes von Sonnenschutzmitteln (ISO/DIS 24443:2020)

Dieses Dokument legt ein In-vitro-Verfahren zur Charakterisierung des UVA-Schutzes von Sonnenschutz-mitteln fest. Es werden Spezifikationen vorgeschlagen, die dazu dienen, eine reproduzierbare Bestimmung der spektralen Extinktion als Charakterisierung des UVA-Schutzes zu ermöglichen.
Zur Bestimmung von für den UVA-Schutz maßgebenden Kenngrößen wurde ein Verfahren zur Aufstellung einer Kurve der spektralen Extinktion im UV-Bereich entwickelt, auf deren Grundlage eine Reihe von Berechnungen und Bewertungen vorgenommen werden können. Ergebnisse dieses Messverfahrens können für weitere Berechnungen, wie z. B. von örtlichen Aufsichtsbehörden gefordert, verwendet werden. Diese umfassen die Berechnung des UVA-Schutzfaktors (UVAPF) [korreliert mit dem In-vivo-UVA-Schutzfaktor aus dem Persistent Pigment Darkening (PPD)-Prüfverfahren], der kritischen Wellenlänge und des UVA-/UVB-Extinktionsverhältnisses. Diese Berechnungen sind optional und beziehen sich auf die örtlichen Anforderungen an die Kennzeichnung von Sonnenschutzmitteln. Dieses Verfahren basiert auf der Verwendung von statischen In-vivo-SPF-Ergebnissen für die Skalierung der UV-Extinktionskurve.
Dieses Dokument gilt nicht für pulverförmige Produkte, die z. B. gepresst oder lose vorliegen.

Détermination in vitro de la photoprotection des produits de protection solaire aux UVA (ISO/DIS 24443:2020)

Kozmetika - Določevanje zaščitnega faktorja UVA in vitro (ISO/DIS 24443:2020)

General Information

• Status: Not Published
• ICS: 11.100.10 - In vitro diagnostic test systems
• ICS: 71.100.70 - Cosmetics. Toiletries
• Technical Committee: CEN/TC 392 - Cosmetics
• Drafting Committee: CEN/TC 392 - Cosmetics
• Current Stage: 4599 - Dispatch of FV draft to CMC - Finalization for Vote
• Due Date: 09-Jun-2021
• Completion Date: 09-Jun-2021
• Mandate: M/389 - Standardisation mandate assigned to CEN concerning methods for testing efficacy of suncreen products
• Ref Project: oSIST prEN ISO 24443:2020 - Determination of sunscreen UVA photoprotection in vitro (ISO/DIS 24443:2020)

RELATIONS

• Revised: EN ISO 24443:2012 - Determination of sunscreen UVA photoprotection in vitro (ISO 24443:2012)
• Effective Date: 06-Dec-2017

Standards Content (sample)

SLOVENSKI STANDARD
oSIST prEN ISO 24443:2020
01-junij-2020
Kozmetika - Določevanje zaščitnega faktorja UVA in vitro (ISO/DIS 24443:2020)
Determination of sunscreen UVA photoprotection in vitro (ISO/DIS 24443:2020)

In vitro Bestimmung des UVA-Schutzes von Sonnenschutzmitteln (ISO/DIS 24443:2020)

Détermination in vitro de la photoprotection UVA (ISO/DIS 24443:2020)
Ta slovenski standard je istoveten z: prEN ISO 24443 rev
ICS:
71.100.70 Kozmetika. Toaletni Cosmetics. Toiletries
pripomočki
oSIST prEN ISO 24443:2020 en,fr,de

2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

---------------------- Page: 1 ----------------------
oSIST prEN ISO 24443:2020
---------------------- Page: 2 ----------------------
oSIST prEN ISO 24443:2020
DRAFT INTERNATIONAL STANDARD
ISO/DIS 24443
ISO/TC 217 Secretariat: ISIRI
Voting begins on: Voting terminates on:
2020-04-30 2020-07-23
Determination of sunscreen UVA photoprotection in vitro
Détermination in vitro de la photoprotection UVA
ICS: 71.100.70
THIS DOCUMENT IS A DRAFT CIRCULATED
This document is circulated as received from the committee secretariat.
FOR COMMENT AND APPROVAL. IT IS
THEREFORE SUBJECT TO CHANGE AND MAY
NOT BE REFERRED TO AS AN INTERNATIONAL
STANDARD UNTIL PUBLISHED AS SUCH.
IN ADDITION TO THEIR EVALUATION AS
ISO/CEN PARALLEL PROCESSING
BEING ACCEPTABLE FOR INDUSTRIAL,
TECHNOLOGICAL, COMMERCIAL AND
USER PURPOSES, DRAFT INTERNATIONAL
STANDARDS MAY ON OCCASION HAVE TO
BE CONSIDERED IN THE LIGHT OF THEIR
POTENTIAL TO BECOME STANDARDS TO
WHICH REFERENCE MAY BE MADE IN
Reference number
NATIONAL REGULATIONS.
ISO/DIS 24443:2020(E)
RECIPIENTS OF THIS DRAFT ARE INVITED
TO SUBMIT, WITH THEIR COMMENTS,
NOTIFICATION OF ANY RELEVANT PATENT
RIGHTS OF WHICH THEY ARE AWARE AND TO
PROVIDE SUPPORTING DOCUMENTATION. ISO 2020
---------------------- Page: 3 ----------------------
oSIST prEN ISO 24443:2020
ISO/DIS 24443:2020(E)
COPYRIGHT PROTECTED DOCUMENT
© ISO 2020

All rights reserved. Unless otherwise specified, or required in the context of its implementation, no part of this publication may

be reproduced or utilized otherwise in any form or by any means, electronic or mechanical, including photocopying, or posting

on the internet or an intranet, without prior written permission. Permission can be requested from either ISO at the address

below or ISO’s member body in the country of the requester.
ISO copyright office
CP 401 • Ch. de Blandonnet 8
CH-1214 Vernier, Geneva
Phone: [phone]
Fax: [phone]
Email: [e-mail]
Website: www.iso.org
Published in Switzerland
ii © ISO 2020 – All rights reserved
---------------------- Page: 4 ----------------------
oSIST prEN ISO 24443:2020
ISO/DIS 24443:2020(E)
Contents Page

Foreword ........................................................................................................................................................................................................................................iv

Introduction ..................................................................................................................................................................................................................................v

1 Scope ................................................................................................................................................................................................................................. 1

2 Normative references ...................................................................................................................................................................................... 1

3 Terms and definitions ..................................................................................................................................................................................... 1

4 Principle ........................................................................................................................................................................................................................ 3

5 Apparatus ..................................................................................................................................................................................................................... 3

5.1 UV spectrophotometer specifications ................................................................................................................................. 3

5.2 Calibration of the UV spectrophotometer........................................................................................................................ 4

5.3 Calibration of the UV exposure source ............................................................................................................................... 4

5.4 Monitoring of the UV exposure source ............................................................................................................................... 4

5.5 Calibration of the UVA radiometer used to monitor the test sample irradiation .......................... 5

5.6 Substrate/plate ....................................................................................................................................................................................... 5

6 Test method ............................................................................................................................................................................................................... 5

6.1 Outline of the test procedure ...................................................................................................................................................... 5

6.2 Equipment calibration and validation of test plates............................................................................................... 6

6.3 Absorption measurements through the plate .............................................................................................................. 6

6.4 Sample application .............................................................................................................................................................................. 6

6.5 Absorbance measurements of the product-treated plate .................................................................................. 7

6.6 Number of determinations ........................................................................................................................................................... 7

6.7 Determination of initial calculated SPF (SPF ), “C” value, initial UVA-PF (UVA-

in vitro

PF ), and UV exposure dose ......................................................................................................................................................... 7

6.7.1 Determination of SPF ......................................................................................................................................

in vitro 7

6.7.2 Determination of “C” value ...................................................................................................................................... 8

6.7.3 Determination of initial UVA protection factor before UV exposure (UVA-PF ) ....... 8

6.7.4 Determination of the UV exposure dose...................................................................................................... 9

6.8 UV exposure ............................................................................................................................................................................................... 9

6.9 Measurement of final adjusted absorbance spectrum ......................................................................................... 9

6.10 Calculation of UVA-PF of plates after UV exposure of the sample ...........................................................10

6.11 Calculation of critical wavelength of plates after UV exposure of the sample ..............................10

7 Procedure using the spreadsheet in this document .....................................................................................................10

8 Product reference sunscreen ...............................................................................................................................................................11

8.1 Formula S2 ...............................................................................................................................................................................................11

8.2 Standard P8 .............................................................................................................................................................................................11

9 Test report ................................................................................................................................................................................................................12

Annex A (normative) Calibration of UV spectrophotometer and plate transmission test.........................13

Annex B (normative) Radiometer calibration to spectroradiometric irradiance procedure ................17

Annex C (normative) Computation values: PPD and erythema action spectra and UVA and

UV-SSR spectral irradiances ...................................................................................................................................................................19

Annex D (normative) PMMA test plate surface specifications ................................................................................................22

Annex E (normative) UVA Product reference sunscreen S2 ......................................................................................................25

Annex F (informative) Statistical calculations .........................................................................................................................................31

Bibliography .............................................................................................................................................................................................................................34

© ISO 2020 – All rights reserved iii
---------------------- Page: 5 ----------------------
oSIST prEN ISO 24443:2020
ISO/DIS 24443:2020(E)
Foreword

ISO (the International Organization for Standardization) is a worldwide federation of national standards

bodies (ISO member bodies). The work of preparing International Standards is normally carried out

through ISO technical committees. Each member body interested in a subject for which a technical

committee has been established has the right to be represented on that committee. International

organizations, governmental and non-governmental, in liaison with ISO, also take part in the work.

ISO collaborates closely with the International Electrotechnical Commission (IEC) on all matters of

electrotechnical standardization.

The procedures used to develop this document and those intended for its further maintenance are

described in the ISO/IEC Directives, Part 1. In particular, the different approval criteria needed for the

different types of ISO documents should be noted. This document was drafted in accordance with the

editorial rules of the ISO/IEC Directives, Part 2 (see www .iso .org/ directives).

Attention is drawn to the possibility that some of the elements of this document may be the subject of

patent rights. ISO shall not be held responsible for identifying any or all such patent rights. Details of

any patent rights identified during the development of the document will be in the Introduction and/or

on the ISO list of patent declarations received (see www .iso .org/ patents).

Any trade name used in this document is information given for the convenience of users and does not

constitute an endorsement.

For an explanation of the voluntary nature of standards, the meaning of ISO specific terms and

expressions related to conformity assessment, as well as information about ISO's adherence to the

World Trade Organization (WTO) principles in the Technical Barriers to Trade (TBT), see www .iso .org/

iso/ foreword .html.
This document was prepared by Technical Committee ISO/TC 217 Cosmetics.

This second edition cancels and replaces the first edition (ISO 24443:2012), which has been technically

revised.

Any feedback or questions on this document should be directed to the user’s national standards body. A

complete listing of these bodies can be found at www .iso .org/ members .html.
iv © ISO 2020 – All rights reserved
---------------------- Page: 6 ----------------------
oSIST prEN ISO 24443:2020
ISO/DIS 24443:2020(E)
Introduction

This International Standard specifies the procedure to determine the Ultraviolet A Protection Factor

(UVAPF) of a sunscreen product using the in vitro UVAPF according to the principles recommended

by COLIPA in 2011. The outcome of this test method can be used to determine the UVA classification of

topical sunscreen products according to local regulatory requirements.

Topical sunscreen products are primarily rated and labelled according to their ability to protect against

sunburn, using a test method to determine the in vivo Sun Protection Factor (see ISO 24444). This

rating evaluates filtration of sunburn generating radiation across the electromagnetic UV spectrum

(290 nm to 400 nm). However, knowledge of the Sun Protection Factor (SPF) rating does not provide

explicit information on the magnitude of the protection provided specifically in the UVA range of

the spectrum (320 nm to 400 nm), as it is possible to have high SPF products with very modest UVA

protection (e.g. SPF 50 with a UVAPF of only 3 to 4). There is demand among medical professionals,

as well as knowledgeable consumers, to have fuller information on the UVA protection provided by

their sunscreen product, in addition to the SPF, in order to make a more informed choice of product,

providing a more balanced and broader-spectrum protection. Moreover, there also a demand to prevent

UVA-induced darkening of the skin from a cultural point of view even without sunburn. The UVAPF

value of a product provides information on the magnitude of the protection provided explicitly in the

UVA portion of the spectrum, independent of the SPF values.

The test method outlined in this International Standard is derived primarily from the in vitro UVAPF

test method as developed by COLIPA.
© ISO 2020 – All rights reserved v
---------------------- Page: 7 ----------------------
oSIST prEN ISO 24443:2020
---------------------- Page: 8 ----------------------
oSIST prEN ISO 24443:2020
DRAFT INTERNATIONAL STANDARD ISO/DIS 24443:2020(E)
Determination of sunscreen UVA photoprotection in vitro
1 Scope

This document specifies an in vitro procedure to characterize the UVA protection of sunscreen products.

Specifications are proposed to enable determination of the spectral absorbance characteristics of UVA

protection in a reproducible manner.

In order to determine relevant UVA protection parameters, the method has been created to provide an

UV spectral absorbance curve from which a number of calculations and evaluations can be undertaken.

Results from this measurement procedure can be used for other computations, as required by local

regulatory authorities. These include calculation of the Ultraviolet-A protection factor (UVA-PF)

[correlating with in vivo UVA-PF from the persistent pigment darkening (PPD) testing procedure],

critical wavelength and UVA absorbance proportionality. These computations are optional and relate

to local sunscreen product labelling requirements. This method relies on the use of static in vivo SPF

results for scaling the UV absorbance curve.

This document is not applicable to powder products such as pressed powder and loose powder products.

2 Normative references

The following documents are referred to in the text in such a way that some or all of their content

constitutes requirements of this document. For dated references, only the edition cited applies. For

undated references, the latest edition of the referenced document (including any amendments) applies.

ISO 24444, Cosmetics — Sun protection test methods — In vivo determination of the sun protection

factor (SPF)
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.

ISO and IEC maintain terminological databases for use in standardization at the following addresses:

— ISO Online browsing platform: available at https:// www .iso .org/ obp
— IEC Electropedia: available at http:// www .electropedia .org/
3.1
in vitro UVA protection factor
UVA-PF

in vitro UVA protection factor of a sun protection product against UVA radiation, which can be derived

mathematically with in vitro spectral modelling
3.2
in vitro protection factor

SPF , protection factor of a sun protection product against erythema-inducing radiation calculated

in vitro
with spectral modelling
3.3

critical wavelength, calculated from spectral data. It corresponds to the wavelength at which the area

under the absorbance curve represents 90 % of the total area under the curve in the UV region

© ISO 2020 – All rights reserved 1
---------------------- Page: 9 ----------------------
oSIST prEN ISO 24443:2020
ISO/DIS 24443:2020(E)
3.4
[1]
action spectrum for erythema [2].
E(λ)

relative effects of individual spectral bands of an exposure source for an erythema response

3.5
[3]
action spectrum for PPD [4].
P(λ)

relative effects of individual spectral bands of an exposure source for a persistent pigment response

3.6
monochromatic absorbance

sunscreen absorbance at wavelength, λ, related to the sunscreen transmittance, T , by

ATλ =−log

where transmittance, T , is the fraction of incident irradiance transmitted by the sunscreen film

3.7
irradiance

fluence rate per unit area, expressed in W/m , for a defined range of wavelengths

EXAMPLE From 290 nm to 400 nm for UVA + UV-B irradiance; from 320 nm to 400 nm for UVA irradiance.

3.8
spectral irradiance for SPF testing or PPD testing
I(λ)
irradiance per unit wavelength, I(λ), expressed in W/m /nm
3.9
spectrophotometer

equipment for measuring the reflection or transmission properties of a material as a function of

wavelength limited to ultraviolet, visible and short infrared ranges in this document

3.10
spectroradiometer
device designed to measure the spectral density of illuminants
3.11
radiometer
device for measuring the radiant flux (power) of electromagnetic radiation
3.12
reference product
reference sunscreen product used to validate the testing procedure
3.13
solar simulator
Equipment used to simulate the solar irradiance and spectrum.
3.14
substrate plate
Material to which the test product is to be applied.
2 © ISO 2020 – All rights reserved
---------------------- Page: 10 ----------------------
oSIST prEN ISO 24443:2020
ISO/DIS 24443:2020(E)
4 Principle

The test is based on the assessment of UV-transmittance through a thin film of sunscreen sample spread

on a roughened substrate, before and after exposure to a controlled dose of radiation from a defined UV

exposure source.

Because of the several variables that cannot be controlled with typical thin film spectroscopic

techniques, each set of sunscreen transmission data is mathematically adjusted so that the in vitro

SPF data yield the same measured in vivo SPF value that was determined by in vivo testing. As in vivo

method could raise ethical consideration, any alternative SPF method, published as an ISO method, may

be used.

Samples are then exposed to a specific measured dose of UV radiation to account for the photostability

characteristics of the test product.

The resulting spectral absorbance data have been shown to be a useful representation of both the

width and height of the UVA protection characteristics of the sunscreen product being tested. The

mathematical modelling procedure has been empirically derived to correlate with human in vivo

(persistent pigment darkening) test results.
5 Apparatus
5.1 UV spectrophotometer specifications

The UV spectrophotometer wavelength range shall span the primary waveband of 290 nm to 400 nm.

The wavelength increment step shall be 1 nm.

A UV spectrophotometer that does not have a monochromator after the test sample should employ a

fluorescence rejection filter.

The UV spectrophotometer input optics should be designed for diffuse illumination and/or diffuse

collection of the transmitted irradiance through the roughened polymethylmethacrylate (PMMA)

substrate, with and without the sunscreen layer spread on its surface.

The size of the diameter of the entrance port of the UV spectrophotometer probe shall be smaller than

the size of the light spot to be measured at the sample level (in order to account for stray light).

The area of each reading site should be at least 0,5 cm in order to reduce the variability between

readings and to compensate for the lack of uniformity in the product layer.

The wavelength should be accurate to within 1 nm, as checked using a holmium-doped filter (see Annex

A). The ability of an instrument to accurately measure absorbance is limited by the sensitivity of the

instrument. The minimum required dynamic range for this methodology is 2,2 absorbance units as

determined according to Annex A.

The maximum measured absorbance should be within the dynamic range of the device used. If

the test measurements yield absorbance curves that exceed the determined upper limit of the UV

spectrophotometer, the product should be re-tested using an instrument with increased sensitivity and

dynamic range.

The lamp in the UV spectrophotometer that is used to measure the transmittance shall emit continuous

radiation over the range of 290 nm to 400 nm, and the level of irradiance should be sufficiently low, so

that the photostability of the product is not unduly challenged (a xenon lamp is a convenient solution).

Therefore, the UV dose during one measurement cycle should not exceed 0,2 J/cm .

NOTE A UV spectrophotometer is used to measure the absorbance properties of the sunscreen on the test

plates. A spectroradiometer is used to measure the spectral energy distribution and intensity of the UV exposure

source or the UV spectrophotometer during the absorbance measurement of the sunscreen on the test plate.

Coupled with an UV source, the radiometer can give similar results to a spectrophotometer.

© ISO 2020 – All rights reserved 3
---------------------- Page: 11 ----------------------
oSIST prEN ISO 24443:2020
ISO/DIS 24443:2020(E)
5.2 Calibration of the UV spectrophotometer

The UV spectrophotometer shall be validated every month by measurements of reference materials.

A three-fold test is required, as described in Annex A:
— dynamic range of the UV spectrophotometer;
— linearity test of the UV spectrophotometer;
— wavelength accuracy test.
5.3 Calibration of the UV exposure source

The spectral irradiance at the exposure plane of the UV exposure source that is used for irradiation

(to take into account any photoinstability) shall be as similar as possible to the irradiance at ground

[1] [2]

level under a standard zenith sun. As defined by COLIPA, the reference standard sun has a total

irradiance of 51.4 to 63.7 W/m2 and a UVA to UVB irradiance ratio of 16.9 to 17.5.

Therefore, the UV irradiance shall be within the following acceptance limits (measured at sample

distance).
Table 1 — UV exposure source specifications
UV exposure source specifications as measured with a spectroradiometer
2 2
Total UV irradiance (290 nm to 400 nm) 40 W/m to 200 W/m
a b
Irradiance ratio of UVA to UVB 11-22
320 nm to 400 nm.
290 nm to 320 nm.

In broad-beam UV-sources, spectra from different locations under the beam shall be recorded over at

least 5 different locations (a location is defined for each plate) in order to account for uniformity.

The uniformity shall be ≥ 90% as calculated by the equation:
(1-(max-min)/(average))% ≥ 90% *

*If the uniformity is less than 90%, then optical components should be adjusted or appropriate

compensation for different irradiance shall be made in the exposure time on each plate.

The UV exposure source device should have the ability to maintain samples within the range of 27 °C

to 32 °C, with intra laboratory temperature ± 2 °C. It is important that the temperature of the sample

itself on the plate shall be measured and not just the surrounding air temperature. Therefore, the

measurement of the temperature shall be on plate level.

To maintain samples at required temperature, a filter system that particularly reduces Infrared

radiation shall be used to achieve the specified temperature range. Cooling trays for the sample plates

or ventilators shall be used to maintain a temperature lower than 32 °C and warming devices to

maintain samples at or above 27 °C.

Measurement to be made using a sensor that is traceable to a national or an international calibration

standard, within the range of use.
5.4 Monitoring of the UV exposure source

The emission of the UV exposure source used for exposure shall be checked for compliance with the

given acceptance limits by a suitably qualified expert (at least) every 12 months, or 2500 hours of lamp

running time. The inspection should be conducted with a spectroradiometer that has been calibrated

against a standard lamp that is traceable to a national or an international calibration standard provided

4 © ISO 2020 – All rights reserved
---------------------- Page: 12 ----------------------
oSIST prEN ISO 24443:2020
ISO/DIS 24443:2020(E)

by an accredited ISO17025 laboratory. In addition to the spectroradiometric inspection, the intensity of

the UV exposure source used for exposure shall be checked prior to each use.

This can be done using either a spectroradiometer or a radiometer with sensitivity in the UVA,

calibrated for the same UV exposure source spectrum used for the exposure step of the procedure,

applying the coefficient of calibration to adjust for variance between the UVA radiometer and the

reference spectroradiometer.

5.5 Calibration of the UVA radiometer used to monitor the test sample irradiation

If a UVA radiometer is used, this device shall have been suitably calibrated. This requires that it be

calibrated to the spectroradiometer used to measure the exposure source (as during annual solar

simulator calibration).

Calibration shall be conducted in terms of UVA irradiance (320 nm to 400 nm) and shall be at the

same level at which the test plates are exposed. Once calibrated with the spectroradiometer, the UVA

radiometer may be used to determine the UV doses to be used during the exposure procedure on a day-

to-day basis. Annex B provides the step-by-step calibration procedure.
5.6 Substrate/plate

The substrate/plate is the material to which the test product is to be applied. For this method, PMMA

plates with one rough side of the substrate are to be used and are commercially available. The size of

the substrate should be chosen such that the application area is not less than 16 cm .

[9]

The specifications and preparation of this type of plate are described in Annex D.

6 Test method
6.1 Outline of the test procedure

6.1.1 Conduct the calibration and validation of the test equipment, including the UV spectrophotometer

used for transmission/absorbance measurements and the UVA radiometer (or spectroradiometer) used

to measure the UV exposure source, and verify the transmission properties of the test plates as described

in Annex D.

6.1.2 Conduct blank measurements of a glycerin-treated or Vaseline-treated plate for the reference

“blank”, which will be used in the subsequent absorbance measurements.

6.1.3 Conduct in vitro absorbance measurements of the sunscreen product spread on a PMMA plate,

prior to any UV irradiation. Acquire the initial mAf spectrum with A (λ) data.

6.1.4 Conduct the mathematical adjustment of the initial UV absorbance spectrum using coefficient

“C” (see the calculation in 6.7.2) to achieve an in vitro SPF (no UV dose) equal to the measured static in

vivo SPF. Initial UVA-PF is calculated using A (λ) and C. A single UV exposure dose, D, is calculated, equal

0 0
to 1,2 × UVA-PF in J/cm , for each plate

6.1.5 Conduct UV exposure of the same sample as in 6.1.3, according to the calculated UV exposure

dose D.

6.1.6 Measure the in vitro absorbance of the sunscreen product after UV exposure. Acquire the second

UV spectrum with A(λ) data.
© ISO 2020 – All rights reserved 5
---------------------- Page: 13 ----------------------
oSIST prEN ISO 24443:2020
ISO/DIS 24443:2020(E)

6.1.7 Conduct the mathematical adjustment of the second mAf spectrum (following UV exposure) by

multiplying with the same “C” coefficient, previously determined in 6.1.4. The resulting absorbance curve

is the final adjusted absorbance values.
6.2 Equipment calibration and validation of test plates

Test procedures as described in Annex A are to be completed to validate the wavelength accuracy,

linearity and absorbance limits of the UV spectrophotometer/spectroradiometer to be used for the test

procedure. Validation of the UV properties of the test PMMA plates shall also be conducted as described

in Annex D.
6.3 Absorption measurements through the plate

It is necessary to first determine the absorbance of UV radiation through a “blank” PMMA plate.

Prepare a “blank” plate by spreading a few microlitres of glycerin/vaseline on the roughened side of the

plate. Choose the amount of glycerine/vaseline such that the entire surface is just completely covered

(approximately 15 μl for a 50 mm × 50 mm plate).
Any excess of
...