Clothes washing machines and washer-dryers for household and similar use - Method for the determination of rinsing effectiveness by measurement of the surfactant content at textile materials

This Technical Specification provides a method for the evaluation of the rinsing effectiveness of household clothes washing machines, washer dryers and commercial washing machines. The amount of residual linear alkylbenzene sulfonate surfactant (LAS) extracted from the unstained test swatches of the strips used in the washing performance test is determined. This is accomplished by measuring the ultraviolet (UV) light absorbance at the wavelength particular to LAS, a key ingredient of the detergent.
Assuming a fixed linear relationship between LAS amount and quantity of detergent mixture and using a concentration versus absorbance curve developed as part of this procedure, the absorbance values are then converted into detergent concentrations, which together with the test solution mass data, yields detergent quantities. This assumption is done, because in the frame of this test it is not possible to determine the exact amount of LAS involved, even in the concentration curves, but only the amount of detergent used.
On the textiles, this linear relationship is not given, but it is nevertheless used to express the amount of LAS as determined by UV light absorbance measurements in terms of a detergent amount.
Using a concentration versus absorbance curve developed as part of this procedure, the absorbance values can then be converted into detergent concentrations, which together with the test solution mass data, yields detergent quantities.

Waschmaschinen und Waschtrockner für den Hausgebrauch und ähnlichen Gebrauch - Methode zur Bestimmung der Spülwirkung durch Messung des Tensidgehalts an Textilien

This Technical Specification provides a method for the evaluation of the rinsing effectiveness of household clothes washing machines, washer dryers and commercial washing machine. The amount of residual detergent extracted from the unstained swatches of the strips used in the washing performance test is determined. This is accomplished by measuring the ultraviolet light absorbance at the wavelength particular to linear alkylbenzene sulfonate surfactant, a key ingredient of the detergent with a known linear relationship to the quantity of detergent mixture.
Using a concentration versus absorbance curve developed as part of this procedure, the absorbance values can then be converted into detergent concentrations, which together with the test solution mass data, yields detergent quantities.
NOTE:  The precision and bias of this measurement is under investigation.

Machines à laver le linge et machines à laver et à sécher pour usages domestiques et analogues - Méthode pour la détermination de l'efficacité de rinçage par la mesure de la teneur en tensioactifs des matières textiles

La présente Spécification Technique fournit une méthode pour l'évaluation de l'efficacité de rinçage des machines à laver le linge à usage domestique, des machines lavantes-séchantes et des machines à laver à usage commercial. La quantité d'alkylbenzènesulfonate linéaire tensioactif (LAS) résiduel extraite à partir des pièces d'essai non salies des bandes utilisées pour l'essai d'aptitude à la fonction de lavage est déterminée, en mesurant l'absorbance de la lumière ultraviolette (UV) à la longueur d'onde spécifique du LAS, un ingrédient essentiel du détergent. En prenant pour hypothèse une relation linéaire fixe entre la quantité de LAS et la quantité de mélange détergent et en utilisant une concentration en fonction de la courbe d'absorbance déterminée dans le cadre de cette procédure, les valeurs d'absorbance sont ensuite converties en concentrations de détergent qui, combinées aux données relatives à la masse de la solution d'essai, indiquent les quantités de détergent. Cette hypothèse est admise, car il n'est pas possible dans le cadre de cet essai de déterminer la quantité exacte de LAS employée, même avec les courbes de concentration, mais uniquement la quantité de détergent utilisée. Sur les textiles, cette relation linéaire n'est pas indiquée, mais elle est néanmoins utilisée pour exprimer la quantité de LAS déterminée par les mesures d'absorbance de la lumière UV pour une quantité de détergent. En utilisant une concentration en fonction de la courbe d'absorbance déterminée dans le cadre de cette procédure, les valeurs d'absorbance peuvent ensuite être converties en concentrations de détergent qui, combinées aux données relatives à la masse de la solution d'essai, indiquent les quantités de détergent.

Pralni in pralno-sušilni stroji za gospodinjsko in podobno uporabo - Metoda za ugotavljanje učinkovitosti izpiranja z merjenjem tenzidov na tekstilu

Ta tehnična specifikacija ponuja metodo za vrednotenje učinkovitosti izpiranja gospodinjskih pralnih strojev, pralno-sušilnih strojev in komercialnih pralnih strojev. Določi se količina ostankov linearnega alkilbenzensulfonatnega tenzida (LAS), izluščenega iz nepobarvanih preskusnih vzorcev trakov, uporabljenih pri preskusu učinkovitosti pranja. To se doseže z merjenjem vpijanja ultravijolične (UV) svetlobe pri valovni dolžini, značilni za linearni alkilbenzensulfonatni tenzid, ki je ključna sestavina detergenta.
Če predpostavimo, da je med količino linearnega alkilbenzensulfonatnega tenzida in količino mešanice detergenta fiksno linearno razmerje ter če uporabimo krivuljo koncentracije v primerjavi z vpojnostjo, ki je pripravljena kot del tega postopka, se vrednosti vpojnosti nato pretvorijo v koncentracije detergenta, ki skupaj s podatki o masi preskusne raztopine zagotavlja podatke o količinah detergenta. Ta predpostavka se uporabi, ker v okviru preskusa ni mogoče določiti natančne količine vpletenega linearnega alkilbenzensulfonatnega tenzida, niti na koncentracijskih krivuljah, ampak zgolj količino uporabljenega detergenta.
Na tkaninah to linearno razmerje ni podano, vendar se kljub temu uporablja za izražanje količine linearnega alkilbenzensulfonatnega tenzida, ugotovljene z meritvami vpijanja UV-svetlobe, na podlagi količine detergenta.
Če uporabimo krivuljo koncentracije v primerjavi z vpojnostjo, ki je pripravljena kot del tega postopka, se vrednosti vpojnosti nato pretvorijo v koncentracije detergenta, ki skupaj s podatki o masi preskusne raztopine zagotavlja podatke o količinah detergenta.

General Information

Status
Published
Publication Date
14-May-2019
Current Stage
6060 - National Implementation/Publication (Adopted Project)
Start Date
19-Apr-2019
Due Date
24-Jun-2019
Completion Date
15-May-2019

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SLOVENSKI STANDARD
SIST-TS CLC/TS 50677:2019
01-junij-2019
Pralni in pralno-sušilni stroji za gospodinjsko in podobno uporabo - Metoda za
ugotavljanje učinkovitosti izpiranja z merjenjem tenzidov na tekstilu

Clothes washing machines and washer-dryers for household and similar use - Method

for the determination of rinsing effectiveness by measurement of the surfactant content

at textile materials
Waschmaschinen und Waschtrockner für den Hausgebrauch und ähnlichen Gebrauch -
Methode zur Bestimmung der Spülwirkung durch Messung des Tensidgehalts an
Textilien

Machines à laver le linge et machines à laver et à sécher pour usages domestiques et

analogues - Méthode pour la détermination de l'efficacité de rinçage par la mesure de la

teneur en tensioactifs des matières textiles
Ta slovenski standard je istoveten z: CLC/TS 50677:2019
ICS:
97.060 Aparati za nego perila Laundry appliances
SIST-TS CLC/TS 50677:2019 en,fr

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

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SIST-TS CLC/TS 50677:2019
TECHNICAL SPECIFICATION CLC/TS 50677
SPÉCIFICATION TECHNIQUE
TECHNISCHE SPEZIFIKATION
March 2019
ICS 97.060
English Version
Clothes washing machines and washer-dryers for household and
similar use - Method for the determination of rinsing
effectiveness by measurement of the surfactant content at textile
materials

Machines à laver le linge et machines à laver et à sécher Waschmaschinen und Waschtrockner für den

pour usages domestiques et analogues - Méthode pour la
Hausgebrauch und ähnliche Zwecke - Verfahren zur

détermination de l'efficacité de rinçage par la mesure de la Bestimmung der Spülwirkung durch Messung des

teneur en tensioactifs des matières textiles Tensidgehalts an Textilien
This Technical Specification was approved by CENELEC on 2018-12-31.

CENELEC members are required to announce the existence of this TS in the same way as for an EN and to make the TS available promptly

at national level in an appropriate form. It is permissible to keep conflicting national standards in force.

CENELEC members are the national electrotechnical committees of Austria, Belgium, Bulgaria, Croatia, Cyprus, the Czech Republic,

Denmark, Estonia, Finland, Former Yugoslav Republic of Macedonia, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia,

Lithuania, Luxembourg, Malta, the Netherlands, Norway, Poland, Portugal, Romania, Serbia, Slovakia, Slovenia, Spain, Sweden,

Switzerland, Turkey and the United Kingdom.
European Committee for Electrotechnical Standardization
Comité Européen de Normalisation Electrotechnique
Europäisches Komitee für Elektrotechnische Normung
CEN-CENELEC Management Centre: Rue de la Science 23, B-1040 Brussels

© 2019 CENELEC All rights of exploitation in any form and by any means reserved worldwide for CENELEC Members.

Ref. No. CLC/TS 50677:2019 E
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Contents Page

European foreword .............................................................................................................................................5

1 Scope ......................................................................................................................................................6

2 Normative references ............................................................................................................................6

3 Terms and definitions ...........................................................................................................................6

4 Symbols and abbreviated terms ..........................................................................................................6

4.1 The variables for Rinse Effectiveness calculations are defined as: ................................................6

4.2 Symbols relating to Annex A ................................................................................................................7

5 Requirements .........................................................................................................................................7

6 Test method ...........................................................................................................................................8

6.1 Equipment and materials ......................................................................................................................8

6.1.1 Climate chamber ....................................................................................................................................8

6.1.2 Ultraviolet (UV) spectrophotometer .....................................................................................................8

6.1.3 Quartz cuvette ........................................................................................................................................8

6.1.4 Cuvette rack ...........................................................................................................................................8

6.1.5 Orbital shaker .........................................................................................................................................8

6.1.6 Scale for weighing detergent and samples ........................................................................................8

6.1.7 Weigh bowl .............................................................................................................................................9

6.1.8 Volumetric flask .....................................................................................................................................9

6.1.9 Graduated cylinder, 100 ml ...................................................................................................................9

6.1.10 Magnetic stirrer ......................................................................................................................................9

6.1.11 Magnetic stir bar ....................................................................................................................................9

6.1.12 Pipette .....................................................................................................................................................9

6.1.13 Disposable glass pipettes (e.g. Pasteur pipettes) ..............................................................................9

6.1.14 Pipette bulbs, 2 ml or greater ...............................................................................................................9

6.1.15 Sample bottle with cap (for test swatch extraction) ..........................................................................9

6.1.16 Laboratory wipes ...................................................................................................................................9

6.1.17 Distilled water ........................................................................................................................................9

6.1.18 Squirt bottle ......................................................................................................................................... 10

6.1.19 Funnel .................................................................................................................................................. 10

6.1.20 Reference detergent A* base powder ............................................................................................... 10

6.2 Preparation of equipment .................................................................................................................. 10

6.2.1 UV spectrophotometer check ............................................................................................................ 10

6.2.2 Cleanliness .......................................................................................................................................... 10

6.2.3 Cuvette filling and cleaning ............................................................................................................... 10

6.2.4 Checking the quality of the distilled water ...................................................................................... 10

6.2.5 Cuvette matching ................................................................................................................................ 13

6.3 Procedure ............................................................................................................................................ 13

6.3.1 Detergent concentration curve ......................................................................................................... 13

6.3.2 Test run procedure ............................................................................................................................. 14

6.3.3 Acquiring samples.............................................................................................................................. 14

6.3.4 UV Absorbance Measurements ......................................................................................................... 15

6.4 Expression of results ......................................................................................................................... 16

6.4.1 Rinsing Effectiveness ........................................................................................................................ 16

6.4.2 Rinse Evenness .................................................................................................................................. 18

7 Data to be reported ............................................................................................................................. 18

Annex A (normative) Procedure for Determining Detergent Concentration Curve ................................. 19

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General approach ................................................................................................................................ 19

A.1

A.2 IEC-A* base detergent sampling ........................................................................................................ 19

A.3 Distilled Water ...................................................................................................................................... 19

A.4 Preparation of Stock 1 solution (IEC-A* base powder detergent) .................................................. 19

A.4.1 Sample Weighing ................................................................................................................................. 19

A.4.2 Mix the Sample .................................................................................................................................... 19

A.4.3 Stock 1 Calculation .............................................................................................................................. 20

A.5 Preparation of Stock 2 ......................................................................................................................... 20

A.5.1 Mix the Sample .................................................................................................................................... 20

A.5.2 Stock 2 Calculation ............................................................................................................................. 20

A.6 Preparation of Working Standards .................................................................................................... 21

A.6.1 Mix the Solutions ................................................................................................................................. 21

A.6.2 Working Standard Calculations ......................................................................................................... 21

A.7 Measure the Absorbance of the Working Standard Solutions ....................................................... 22

A.8 Calculations ......................................................................................................................................... 23

A.8.1 Initial Treatment of the Data ............................................................................................................... 23

A.8.2 Single sample data (per detergent sample) ...................................................................................... 23

A.8.3 Combined sample data (all detergent samples) ............................................................................... 23

Annex B (normative) IEC-A* base powder detergent sampling .................................................................. 24

B.1 Purpose ................................................................................................................................................ 24

B.2 Devices and Materials ......................................................................................................................... 24

B.3 Sampling procedure ............................................................................................................................ 24

Annex C (informative) Acquiring samples using a dispenser .................................................................... 28

C.1 General ................................................................................................................................................. 28

C.2 Calibration of the dispenser ............................................................................................................... 28

C.2.1 General ................................................................................................................................................. 28

C.2.2 Priming ................................................................................................................................................. 28

C.2.3 Setting the volume .............................................................................................................................. 28

C.2.4 Calibration: ........................................................................................................................................... 28

C.2.5 Calculation: .......................................................................................................................................... 29

C.3 Acquiring samples (with dispenser) .................................................................................................. 29

Annex D (informative) Quartz cuvette and glassware cleaning and handling .......................................... 30

D.1 Purpose ................................................................................................................................................ 30

D.2 Cuvettes ................................................................................................................................................ 30

D.3 General Cleaning ................................................................................................................................. 30

D.4 Periodic Glass Cleaning ..................................................................................................................... 31

D.4.1 General ................................................................................................................................................. 31

D.4.2 Standard Glassware Cleaning Solutions .......................................................................................... 31

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Annex E (informative) Uncertainty of the test method ............................................................................... 32

Annex F (informative) Reduction of the test effort ..................................................................................... 33

Annex G (normative) Test report – Data to be recorded ............................................................................ 34

G.1 General ................................................................................................................................................ 34

G.2 Data for test washing machine .......................................................................................................... 34

G.3 Data, parameters and results for the test series ............................................................................. 35

G.4 Example of calibration data collection (including calculation) ..................................................... 36

G.5 Example of data collection for measurement .................................................................................. 38

Bibliography ..................................................................................................................................................... 39

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European foreword

This document (CLC/TS 50677:2019) has been prepared by CLC/TC 59X "Performance of household and

similar electrical appliances".

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

patent rights. CENELEC shall not be held responsible for identifying any or all such patent rights.

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1 Scope

This Technical Specification provides a method for the evaluation of the rinsing effectiveness of household

clothes washing machines, washer dryers and commercial washing machines. The amount of residual

linear alkylbenzene sulfonate surfactant (LAS) extracted from the unstained test swatches of the strips

used in the washing performance test is determined. This is accomplished by measuring the ultraviolet

(UV) light absorbance at the wavelength particular to LAS, a key ingredient of the detergent.

Assuming a fixed linear relationship between LAS amount and quantity of detergent mixture and using a

concentration versus absorbance curve developed as part of this procedure, the absorbance values are

then converted into detergent concentrations, which together with the test solution mass data, yields

detergent quantities. This assumption is done, because in the frame of this test it is not possible to

determine the exact amount of LAS involved, even in the concentration curves, but only the amount of

detergent used.

On the textiles, this linear relationship is not given, but it is nevertheless used to express the amount of

LAS as determined by UV light absorbance measurements in terms of a detergent amount.

Using a concentration versus absorbance curve developed as part of this procedure, the absorbance

values can then be converted into detergent concentrations, which together with the test solution mass

data, yields detergent quantities.
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.

EN 60456:2016, Clothes washing machines for household use — Methods for measuring the performance

(IEC 60456)
3 Terms and definitions
No terms and definitions are listed in this document.

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

— IEC Electropedia: available at http://www.electropedia.org/
— ISO Online browsing platform: available at http://www.iso.org/obp
4 Symbols and abbreviated terms
4.1 The variables for Rinse Effectiveness calculations are defined as:
Asp average absorbance
Asp 1)
avg,j
average net absorbance of the sample j
Asp 1)
i net absorbance for specimen i
Asp 1)
i,223
absorbance reading at 223 nm for specimen i
Asp
i,330 1)
absorbance reading at 330 nm for specimen i
Asp 1)
m peak absorbance at wavelength m

Care shall be taken in the calculations of Clause 6, as these variables are depending on additional

parameters, e.g. index of the sample, swatch or test run.
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Asp 1)
r,m relative peak absorbance at wavelength m
Cs 1)
j concentration of detergent in sample j
Ds 1)
j mass of detergent recovered from sample j
Dsw
avg,l average ratio of mass of detergent recovered per gram
of test swatch from the test run l
Dsw 1)
k ratio of mass of detergent of test swatch k
DL ratio of mass of detergent of test run l
i, j, k and l index of specimens, samples, swatches and test run
m slope of the detergent concentration curve
n number of cuvettes, specimens, samples, swatches or
test runs
Rinse Effectiveness (average of all test runs)
Re Rinse Evenness Score
S standard deviation of the Rinse Effectiveness
S standard deviation of the ratio of mass of detergent
r,l
recovered per gram of test swatch for test run l
Wsw 1)
k weight of test swatch k
Ws 1)
j weight of water in sample j
4.2 Symbols relating to Annex A
b intercept of the detergent concentration curve
CWSS detergent concentration of Working Standard Solution
m mass of detergent
det
m slope of the detergent concentration curve
m mass of transferred Stock 1 solution
m mass of transferred Stock 2 solution
St concentration of Stock 1 solution
St concentration of Stock 2 solution
y absorbance value of the sample
x concentration of the detergent in the sample
5 Requirements
(Not available in this document.)
Care shall be taken, as numbers of different parameters are different.
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6 Test method
6.1 Equipment and materials

NOTE This materials list is additional to the materials list in EN 60456:2016, 5.4.

6.1.1 Climate chamber

The ambient temperature and relative humidity in the climate chamber shall be maintained at:

— temperature: (20 ± 2) °C
— relative humidity: (65 ± 5) %.
6.1.2 Ultraviolet (UV) spectrophotometer

The absorption of the ultraviolet light shall be measured with a ultraviolet spectrophotometer with the

following specifications:
— wavelength range: 190 nm to 1100 nm
— spectral bandwidth: ≤ 1 nm
— wavelength accuracy (at D peak 656,1 nm): - 0,2 to 0,2 nm

— wavelength repeatability (10 measurements at 656,1 nm, slit width 1 nm): - 0,05 to 0,05 nm

— photometric range: - 0,1 to 3,0 A
— photometric accuracy (UV with K Cr O , Ph.Eur. at 1 A): - 0,02 to 0,02 A
2 2 7

— photometric repeatability (10 measurements with K Cr O , Ph.Eur. at 1 A): - 0,002 to 0,002 nm.

2 2 7

The spectrophotometer has to be calibrated regularly according to the manufacturer’s specification.

6.1.3 Quartz cuvette

The cuvettes to be used for the measurement of the ultraviolet absorption shall be rectangular with a path

length of 10 mm and be made from quartz
6.1.4 Cuvette rack
(Not specified in this document.)
6.1.5 Orbital shaker

The device for the extraction of the linear alkylbenzene sulfonate shall be an orbital shaker. The orbital

shaker shall have a device for securing sample bottles on it.
Orbit: 4 mm to 20 mm
Shaker speed: ≥ 350 r/min

NOTE The speed of the shaker can be checked by a tachometer, either optical by light beam reflection or

mechanical by a magnetic sensor. For details it is advised to refer to the manufacturer’s specification.

6.1.6 Scale for weighing detergent and samples
Minimum specification: 0 to 150 g range with
Minimum resolution: 0,001 g
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Accuracy: ± 0,002 g
6.1.7 Weigh bowl
(Not specified in this document.)
6.1.8 Volumetric flask

For the preparation of the working standards for calibration volumetric flasks with a volume of 100 ml and

1 000 ml shall be used.
6.1.9 Graduated cylinder, 100 ml
(Not specified in this document.)
6.1.10 Magnetic stirrer
(Not specified in this document.)
6.1.11 Magnetic stir bar
Small, medium and large stir bars shall be used.
6.1.12 Pipette
Pipette of volume 1, 2, 5, 10 and 25 ml shall be used.
6.1.13 Disposable glass pipettes (e.g. Pasteur pipettes)

Disposable glass pipettes without cotton stoppers, non sterile and with a volume of 2 ml or greater shall be

used for transferring the extract to the cuvettes.

NOTE A transfer pipette with disposable plastic tips can be used in place of glass pipettes after correlation tests.

6.1.14 Pipette bulbs, 2 ml or greater
(Not specified in this document.)
6.1.15 Sample bottle with cap (for test swatch extraction)

For the extraction of the test swatches plastic bottles with cap made from high-density polyethylene with a

volume of 125 ml and a diameter of 5 cm shall be used.
6.1.16 Laboratory wipes
(Not specified in this document.)
6.1.17 Distilled water

All water used for extractions, dilutions and the preparation of calibration standards shall meet the following

criteria:
Conductivity at 25 °C: ≤ 1 µS/cm.
Net absorbance (223 nm to 330 nm): - 0,002 to 0,002 A.

Absorbance curve spectrum 200 nm to 350 nm: no relative peak absorbance greater than ± 0,002 A in the

range between 223 nm to 330 nm.
The procedure for calculating these values is given in 6.2.4.

NOTE Water prepared by methods other than distillation having equivalent specifications can be used instead of

distilled water.
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6.1.18 Squirt bottle
Material: high-density polyethylene
6.1.19 Funnel
(Not specified in this document.)
6.1.20 Reference detergent A* base powder

The detergent used for calibration is IEC-A* as described in EN 60456:2016. Only the base powder IEC-A*

shall be used for the determination of the calibration curve. The calibration shall be done with the batch of

detergent used for washing.

NOTE This document only refers to IEC-A* as detergent. It is possible to use other detergents than IEC-A*. For

all cases the calibration shall be done with the detergent used for washing.
6.2 Preparation of equipment
(Not specified in this document.)
6.2.1 UV spectrophotometer check

Turn on the UV spectrophotometer. It should be run approximately 30 min before measurements (refer to

the manufacturer’s specification).

If the instrument has a built-in self-check function, perform the self-check once a day before measuring

data. This may be included in the calibration report.
6.2.2 Cleanliness

All materials that come in contact with detergent, distilled water, Stock 1, Stock 2 or the working standard

solutions shall be cleaned and thoroughly rinsed with distilled water then dried before use. A professional

laboratory dishwasher may be used for this purpose.
6.2.3 Cuvette filling and cleaning

The cuvettes should be handled by the opaque sides only. Do not touch the clear sides of the cuvettes.

To avoid air bubbles, fill by running the solution down the side of the cuvette. Fill cuvettes without soiling or

wetting the exterior measuring surface. If air bubbles are present, eliminate them by holding the cuvette at

a slight angle and tapping the opaque side as many times as necessary to release the bubbles.

To prevent liquid from running down the cuvette surface after discharging, place the cuvette head first on a

clean position of a lint-free tissue for some seconds. Replace the tissue from time to time if no clean

position is left.

If a cuvette gets wet on the outside, clean the cuvette and re-check with distilled water. Do not only

wipe/dry the cuvette surface with a tissue. Remaining residues in the UV-area are not visible.

NOTE See Annex D (informative), Quartz cuvette and glassware cleaning and handling.

6.2.4 Checking the quality of the distilled water
6.2.4.1 General

Take a spectrum (200 nm to 350 nm) of the distilled water used for testing as described in 6.2.4.2 f).

a) the calculated net absorbance value (223 nm to 330 nm) is greater than ± 0,002 A

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b) any relative peak absorbance value in the range between 223 nm to 330 nm is greater than ± 0,002 A

Check the spectrum for abnormality and repeat this section with a different batch of distilled water. Such

water is likely to contain impurities which could interfere with this test method and lead to unreliable results.

6.2.4.2 Spectrum from 200 nm to 350 nm
a) Start Spectrophotometer and wait for warm up
b) Use only one cuvette

c) Place a DRY and CLEAN and EMPTY cuvette into the position for zeroing the cuvette. The positioning

of the cuvette may vary according to the type of spectrophotometer used:

— for double beam devices, place the cuvette in the measuring position and leave the

reference/blank position empty;

— for single beam devices with a carrousel, place the cuvette in the reference/blank position.

d) Zero the device (baseline correction)

e) Fill the cuvette with distilled water (rinse twice, keep the third for measurement), place cuvette into the

measuring position,
...

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