Dentistry - Corrosion resistance of dental amalgam (ISO 23325:2020)

This International Standard gives the requirement for the permissible reduction in strength resulting
from crevice corrosion of dental amalgam products that are within the scope of ISO 24234: Dentistry –
Dental amalgam and ISO 20749: Dentistry – Pre-capsulated dental amalgam. It provides details of the
test procedure for determining this.

Zahnheilkunde - Korrosionsbeständigkeit von Dentalamalgam (ISO 23325:2020)

Dieses Dokument beschreibt die Anforderungen an die zulässige Reduzierung der Festigkeit von dentalen Amalgamprodukten, die im Anwendungsbereich von ISO 24234 und ISO 20749 liegen, aufgrund der Spaltkorrosion. Es beschreibt Einzelheiten des Prüfverfahrens um diese zu ermitteln.

Médecine bucco-dentaire - Résistance à la corrosion des amalgames dentaire (ISO 23325:2020)

Le présent document spécifie les exigences applicables à la réduction admissible de la résistance consécutive à la corrosion caverneuse d'amalgames dentaires faisant partie du domaine d'application de l'ISO 24234 ou de l'ISO 20749. Il fournit des informations sur le mode opératoire d'essai applicable à la détermination de cette résistance.

Zobozdravstvo - Odpornost zobnega amalgama proti koroziji (ISO 23325:2020)

General Information

Status
Published
Public Enquiry End Date
04-Jul-2019
Publication Date
13-Aug-2020
Technical Committee
Current Stage
6060 - National Implementation/Publication (Adopted Project)
Start Date
28-Jul-2020
Due Date
02-Oct-2020
Completion Date
14-Aug-2020

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SLOVENSKI STANDARD
SIST EN ISO 23325:2020
01-september-2020
Zobozdravstvo - Odpornost zobnega amalgama proti koroziji (ISO 23325:2020)
Dentistry - Corrosion resistance of dental amalgam (ISO 23325:2020)
Zahnheilkunde - Korrosionsbeständigkeit von Dentalamalgam (ISO 23325:2020)
Médecine bucco-dentaire - Résistance à la corrosion des amalgames dentaire (ISO
23325:2020)
Ta slovenski standard je istoveten z: EN ISO 23325:2020
ICS:
11.060.10 Zobotehnični materiali Dental materials
SIST EN ISO 23325:2020 en

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

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SIST EN ISO 23325:2020
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SIST EN ISO 23325:2020
EN ISO 23325
EUROPEAN STANDARD
NORME EUROPÉENNE
July 2020
EUROPÄISCHE NORM
ICS 11.060.10
English Version
Dentistry - Corrosion resistance of dental amalgam (ISO
23325:2020)

Médecine bucco-dentaire - Résistance à la corrosion Zahnheilkunde - Korrosionsbeständigkeit von

des amalgames dentaires (ISO 23325:2020) Dentalamalgam (ISO 23325:2020)
This European Standard was approved by CEN on 9 June 2020.

CEN members are bound to comply with the CEN/CENELEC Internal Regulations which stipulate the conditions for giving this

European Standard the status of a national standard without any alteration. Up-to-date lists and bibliographical references

concerning such national standards may be obtained on application to the CEN-CENELEC Management Centre or to any CEN

member.

This European Standard exists in three official versions (English, French, German). A version in any other language made by

translation under the responsibility of a CEN member into its own language and notified to the CEN-CENELEC Management

Centre has the same status as the official versions.

CEN members are the national standards bodies of Austria, Belgium, Bulgaria, Croatia, Cyprus, Czech Republic, Denmark, Estonia,

Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway,

Poland, Portugal, Republic of North Macedonia, Romania, Serbia, Slovakia, Slovenia, Spain, Sweden, Switzerland, Turkey and

United Kingdom.
EUROPEAN COMMITTEE FOR STANDARDIZATION
COMITÉ EUROPÉEN DE NORMALISATION
EUROPÄISCHES KOMITEE FÜR NORMUNG
CEN-CENELEC Management Centre: Rue de la Science 23, B-1040 Brussels

© 2020 CEN All rights of exploitation in any form and by any means reserved Ref. No. EN ISO 23325:2020 E

worldwide for CEN national Members.
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SIST EN ISO 23325:2020
EN ISO 23325:2020 (E)
Contents Page

European foreword ....................................................................................................................................................... 3

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SIST EN ISO 23325:2020
EN ISO 23325:2020 (E)
European foreword

This document (EN ISO 23325:2020) has been prepared by Technical Committee ISO/TC 106

"Dentistry" in collaboration with Technical Committee CEN/TC 55 “Dentistry” the secretariat of which

is held by DIN.

This European Standard shall be given the status of a national standard, either by publication of an

identical text or by endorsement, at the latest by January 2021, and conflicting national standards shall

be withdrawn at the latest by January 2021.

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

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

According to the CEN-CENELEC Internal Regulations, the national standards organizations of the

following countries are bound to implement this European Standard: Austria, Belgium, Bulgaria,

Croatia, Cyprus, Czech Republic, Denmark, Estonia, Finland, France, Germany, Greece, Hungary, Iceland,

Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Republic of

North Macedonia, Romania, Serbia, Slovakia, Slovenia, Spain, Sweden, Switzerland, Turkey and the

United Kingdom.
Endorsement notice

The text of ISO 23325:2020 has been approved by CEN as EN ISO 23325:2020 without any modification.

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SIST EN ISO 23325:2020
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SIST EN ISO 23325:2020
INTERNATIONAL ISO
STANDARD 23325
First edition
2020-06
Dentistry — Corrosion resistance of
dental amalgam
Médecine bucco-dentaire — Résistance à la corrosion des amalgames
dentaires
Reference number
ISO 23325:2020(E)
ISO 2020
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SIST EN ISO 23325:2020
ISO 23325:2020(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: +41 22 749 01 11
Email: copyright@iso.org
Website: www.iso.org
Published in Switzerland
ii © ISO 2020 – All rights reserved
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SIST EN ISO 23325:2020
ISO 23325:2020(E)
Contents Page

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

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

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

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

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

4 Sampling ........................................................................................................................................................................................................................ 3

5 Requirement ............................................................................................................................................................................................................. 3

6 Preparation of the dental amalgam test-piece ...................................................................................................................... 4

6.1 General ........................................................................................................................................................................................................... 4

6.1.1 Temperature ........................................................................................................................................................................ 4

6.1.2 Mixing ........................................................................................................................................................................................ 4

6.2 Apparatus for the preparation of the dental amalgam test-piece ............................................................... 4

6.3 Materials and tolerances for construction of the mould ..................................................................................... 4

6.4 Packing the mould, removal of test-piece and inspection for surface defects ................................. 5

7 Test solution (artificial saliva) ............................................................................................................................................................... 6

7.1 Reagents........................................................................................................................................................................................................ 6

7.2 Stock solutions ........................................................................................................................................................................................ 7

7.2.1 Stock Solution A ................................................................................................................................................................ 7

7.2.2 Stock Solution B ................................................................................................................................................................ 7

7.2.3 Stock Solution C ................................................................................................................................................................ 7

7.3 Test solution .............................................................................................................................................................................................. 7

8 Procedure for test-piece conditioning ........................................................................................................................................... 8

8.1 Apparatus .................................................................................................................................................................................................... 8

8.2 Control test-pieces ............................................................................................................................................................................... 8

8.3 Corrosion test-pieces ......................................................................................................................................................................... 9

8.4 Replacement test-pieces ................................................................................................................................................................. 9

9 Mechanical testing .............................................................................................................................................................................................. 9

9.1 Apparatus for mechanical testing ........................................................................................................................................... 9

9.2 Procedure .................................................................................................................................................................................................10

9.2.1 Loading arrangement ...............................................................................................................................................10

9.2.2 Force application and fracture ..........................................................................................................................11

9.3 Treatment of data ..............................................................................................................................................................................11

10 Test report ................................................................................................................................................................................................................12

Bibliography .............................................................................................................................................................................................................................13

© ISO 2020 – All rights reserved iii
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SIST EN ISO 23325:2020
ISO 23325:2020(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 106, Dentistry, Subcommittee SC 1, Filling

and restorative materials, in collaboration with the European Committee for Standardization (CEN)

Technical Committee CEN/TC 55, Dentistry, in accordance with the Agreement on technical cooperation

between ISO and CEN (Vienna Agreement).

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
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SIST EN ISO 23325:2020
ISO 23325:2020(E)
Introduction

This document sets a requirement, being the acceptable limit, for the reduction in strength of dental

amalgam that is a consequence of crevice corrosion when the test is conducted using the procedure

specified in this document. It uses one of the three corrosion test procedures present in ISO/TS 17988

for which a requirement is given in this document. The testing protocol is designed to accelerate the

effect, such that results are obtained in a time suited to an in vitro test. Its purpose is to differentiate

acceptable products from those that are not (by using a benchmark value) and not to rank products. It

is not intended for use in product comparison claims.

Specific qualitative and quantitative requirements for freedom from biological hazard are not

included in this document, but it is recommended that reference be made to ISO 10993-1 and ISO 7405

for assessing possible biological hazards. The test procedure in this document is inappropriate for

assessing possible biological hazards.
© ISO 2020 – All rights reserved v
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SIST EN ISO 23325:2020
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SIST EN ISO 23325:2020
INTERNATIONAL STANDARD ISO 23325:2020(E)
Dentistry — Corrosion resistance of dental amalgam
1 Scope

This document specifies the requirements for the permissible reduction in strength resulting from

crevice corrosion of dental amalgam products that are within the scope of ISO 24234 or ISO 20749. It

provides details of the test procedure for determining this.
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 1942, Dentistry — Vocabulary
ISO 3696, Water for analytical laboratory use — Specification and test methods

ISO 4287, Geometrical Product Specifications (GPS) — Surface texture: Profile method — Terms, definitions

and surface texture parameters

ISO 6344-1, Coated abrasives — Grain size analysis — Part 1: Grain size distribution test

ISO 7488, Dentistry — Mixing machines for dental amalgam
ISO 13897, Dentistry — Dental amalgam reusable mixing-capsules
ISO 24234, Dentistry — Dental amalgam
3 Terms and definitions

For the purposes of this document, the terms and definitions given in ISO 1942 and the following apply.

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

— ISO Online browsing platform: available at http:// www .iso .org/ obp
— IEC Electropedia: available at http:// www .electropedia .org/
3.1
dental amalgam alloy

alloy in fine particles, composed mainly of silver, tin and copper, which when mixed with dental mercury

(3.2), produces a dental amalgam for dental restoration
[SOURCE: ISO 20749:2017, 3.1]
3.2
dental mercury
mercury supplied for use in the preparation of dental amalgam
[SOURCE: ISO 20749:2017, 3.2]
© ISO 2020 – All rights reserved 1
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SIST EN ISO 23325:2020
ISO 23325:2020(E)
3.3
pre-capsulated product

product supplied in a sealed capsule that contains measured amounts of dental amalgam alloy (3.1)

powder and dental mercury (3.2) with masses that are appropriate for the production of a mass of dental

amalgam that is considered to be suitable for a single small or medium size restoration in a single tooth

Note 1 to entry: The dental amalgam alloy powder and dental mercury are separated by a barrier that is broken

immediately prior to mixing, allowing their contact. The capsule remains sealed until mixing has been completed.

[SOURCE: ISO 20749:2017, 3.3]
3.4
dental amalgam alloy tablet

quantity of dental amalgam alloy (3.1) powder that has been compressed to form a single entity for the

purpose of providing a pre-dosed quantity of the alloy that, when mixed with an appropriate mass of

dental mercury (3.2), produces a mass of dental amalgam that is considered to be suitable for a single

small or medium size restoration in a single tooth

Note 1 to entry: During mixing, the tablet is intended to break apart, forming a fine powder.

[SOURCE: ISO/TS 20746:2016, 3.4]
3.5
dental mercury sachet

measured quantity of dental mercury (3.2) supplied in a sachet (for use in a reusable mixing capsule)

in a mass that, when mixed with an appropriate mass of dental amalgam alloy (3.1), produces a mass

of dental amalgam that is considered to be suitable for a single small or medium size restoration in a

single tooth

Note 1 to entry: The sachet is intended to rupture during mixing to allow the dental mercury to come into contact

with the dental amalgam alloy powder.

Note 2 to entry: A dental mercury sachets may be referred to as a dental mercury pillow.

[SOURCE: ISO/TS 20746:2016, 3.5]
3.6
hertzian-loading strength-reduction corrosion test

test in which a test-piece is immersed for a defined period of time in a specified solution (at a specified

temperature) in a way that creates crevice corrosion conditions on one surface, after which it is removed

from the solution and fractured with the force to do this then compared with the force to fracture an

identical test-piece subjected to ageing in air at the same temperature

Note 1 to entry: Fracture is initiated from the surface subjected to crevice corrosion conditions and proceeds by

radial crack growth.
[SOURCE: ISO/TS 17988: 2014, 3.8]
3.7
radial cracking

fracture pattern of a Hertzian-loaded test-piece in which (more or less) planar cracks form along radii,

normal to the face of the disc shaped test-piece, thus dissecting it into two or more sectors

Note 1 to entry: Such radial cracks initiate on the test surface of the test-piece and propagate through the disc to

produce approximately equiangular dissection in most cases.
2 © ISO 2020 – All rights reserved
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SIST EN ISO 23325:2020
ISO 23325:2020(E)

EXAMPLE Some radial fracture patterns in disc shaped test-pieces are illustrated here:

[SOURCE: ISO/TS 20746:2016, 3.8]
3.8
top surface

surface of the disc shaped test-piece that has been produced by carving back unset amalgam that is

above the level of the mould until the surface of the test-piece is flat and level with that mould surface

[SOURCE: ISO/TS 20746:2016, 3.6]
3.9
test surface

surface of the disc shaped test-piece that has been produced by contact with the polished glass plate

when the mixed amalgam is packed into the mould
[SOURCE: ISO/TS 20746:2016, 3.7]
3.10
mixing machine for dental amalgam
DEPRECATED: amalgamator

electrically-powered mixing machine that operates using an oscillating action for mixing dental

amalgam alloy (3.1) and dental mercury (in a capsule) to produce a dental amalgam

[SOURCE: ISO/TS 17988: 2014, 3.12]
4 Sampling
Products shall be procured in packages that have been produced for retail.

For pre-capsulated dental amalgam products, procure a sufficient number of capsules from a single lot.

For dental amalgam alloy in the form of a powder supplied in bulk or in tablets, procure sufficient dental

amalgam alloy and a sufficient number of dental mercury sachets from single lots. The dental mercury

sachets shall conform to ISO 24234.

NOTE In this context, “sufficient” is deemed to be the quantity to make the required number of test-pieces

and the maximum number of test-pieces allowed to replace any that are rejected.
At least 3,0 g of dental amalgam alloy is required per test-piece.
5 Requirement

When tested in accordance with Clauses 6, 7, 8 and 9 the mean value (in newton) of 10 valid results for

corrosion test-pieces shall not be less than 80 % of the mean value (in newton) of 10 valid results for

control test-pieces.
© ISO 2020 – All rights reserved 3
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SIST EN ISO 23325:2020
ISO 23325:2020(E)
6 Preparation of the dental amalgam test-piece
6.1 General
6.1.1 Temperature
Prepare test-pieces at (23 ± 2) °C.
6.1.2 Mixing

For a dental amalgam alloy product supplied either as tablets or as a free-flowing powder in bulk, the

ratio by mass of the dental amalgam alloy to the mass of dental mercury shall be that recommended by

the manufacturer. Use a reusable mixing-capsule (with a pestle, if needed) that conforms to ISO 13897.

Use any other mixing accessory that is required, as recommended by the manufacturer. If more than

one mix is required to make the test-piece, produce these mixes simultaneously using equipment of the

same type for each mix. However, if the last mix can be produced within the working time of the first

mix, mixing these masses sequentially on a single piece of equipment is permitted.

For pre-capsulated products, use as many capsules as needed. Mix the contents of the capsules either

simultaneously using the same number of mixing machines for dental amalgam of the same type, or

sequentially on a single mixing machine for dental amalgam (the latter is permitted, provided the

mixing of the last capsule is completed before the end of the working time of the first). If necessary, use

only a portion of the dental amalgam mix from one of these capsules.

Use a mixing machine for dental amalgam that conforms to ISO 7488 and that is recommended for mixing

the dental amalgam alloy product with dental mercury or mixing the pre-capsulated product. Use the

mixing machine settings and mixing time that are recommended by the manufacturer of the dental

amalgam alloy or pre-capsulated product (for the mass of dental amalgam alloy that is being mixed).

6.2 Apparatus for the preparation of the dental amalgam test-piece
6.2.1 Mould, as shown in Figure 1.

6.2.2 Flat glass plate, with a polished scratch-free surface and square with an edge length greater

than 30 mm.

6.2.3 Microscope slide, glass, to provide a straight edge to carve back the dental amalgam.

6.2.4 Hand-instrument for dental amalgam packing.
6.2.5 Tweezers, steel.
6.3 Materials and tolerances for construction of the mould

The mould shall be made of hardened tool steel or hardened stainless steel. The upper and lower

surfaces shall be flat and parallel, and have an arithmetic mean roughness (R ) not greater than 6,3 μm

when tested in accordance with ISO 4287. The hole shall have a taper of (7 ± 2)° to allow the amalgam

disc to be ejected without undue force when this is applied to the face that has the smaller diameter. The

tapered surface shall be smooth enough not to impede the ejection of the test-piece. For example, it may

be honed to an arithmetic mean roughness (R ) of 6,3 μm (when tested in accordance with ISO 4287).

NOTE 1 For convenience, to distinguish between the two surfaces during test-piece production, a small

engraved mark (set away from the hole) can be made on one of the mould faces.

NOTE 2 The angle of the taper, (7 ± 2)° is the included angle. The wall of the mould is at an angle of (3,5 ± 1,0)°

with the centre line.
4 © ISO 2020 – All rights reserved
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SIST EN ISO 23325:2020
ISO 23325:2020(E)

It is permissible to use PTFE in the place of steel provided the same dimensional accuracy and surface

roughness exists. Steel is selected for better durability. If PTFE is used, the thickness shall be checked

frequently and the edges of the tapered hole inspected for significant chipping.
6.4 Packing the mould, removal of test-piece and inspection for surface defects

Place the steel mould on the glass plate with the side that has the greater diameter for the tapered hole

in contact with the plate.

NOTE 1 The surface of the glass plate acts as a matrix for the test surface of the test-piece.

Mix a mass of the dental amalgam sufficient to make a disc-shaped test-piece that is 10 mm diameter

and 3 mm high after packing into the die shown in Figure 1.

Transfer pieces of the amalgam paste to the mould by using the tweezers. Using the hand-instrument

for dental amalgam packing (6.2.4), condense the dental amalgam, overfilling slightly. Carve back using

the edge of the microscope slide to produce a flat surface (on the dental amalgam) that is level with that

of the mould.

A razor blade should not be used for carving back excess amalgam. A microscope slide produces a

smoother and more even surface finish.

Allow the dental amalgam to set for 10 min. Carefully eject the test-piece from the mould by applying

light finger-pressure to the surface of the test-piece that has been carved back (the top surface), while

holding the mould in the other hand. Check visually that the test surface is defect-free everywhere, other

than possibly at the margin. Use visual inspection without magnification. Carry out this inspection

at an illuminance of at least 1 000 lux and at a distance not exceeding 250 mm. A person making the

inspection shall have nominally normal visual acuity [corrective (non-magnifying) non-tinted lenses

may be worn]. If a defect is detected, reject that test-piece and make a replacement.

NOTE 2 To prevent any damage to the test surface during ejection, placing a thick soft pad, such as a number of

dental napkins, under the mould to “catch” the ejected test-piece is recommended.

After ejection do not grind or polish the surfaces of the test-piece.
© ISO 2020 – All rights reserved 5
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SIST EN ISO 23325:2020
ISO 23325:2020(E)
Dimensions in millimetres

Figure 1 — Mould to produce disc-shaped test-pieces for the Hertzian-loading strength-

reduction corrosion test
7 Test solution (artificial saliva)
7.1 Reagents

All reagents are to be analytical grade with the exception of lactic acid which is to be ≥85 %.

7.1.1 Sodium dihydrogen phosphate.
7.1.2 Potassium chloride.
7.1.3 Sodium chloride.
7.1.4 Ammonium chloride.
7.1.5 Trisodium citrate dihydrate.
7.1.6 Lactic acid solution.
7.1.7 Urea.
6 © ISO 2020 – All rights reserved
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SIST EN ISO 23325:2020
ISO 23325:2020(E)
7.1.8 Uric acid.
7.1.9 Sodium hydroxide.
7.1.10 Potassium thiocyanate.
7.1.11 Hydrochloric acid.
7.1.12 Water to Grade 2, as specified in ISO 3696.
7.2 Stock solutions

Make the following three stock solutions using water to Grade 2, as specified in ISO 3696. Store these

separately in a refrigerator at (4 ± 2) °C.
7.2.1 Stock Solution A
7.2.1.1 Sodium dihydrogen phosphate, 28,0 g/l.
7.2.1.2 Potassium chloride, 86,8 g/l.
7.2.1.3 Sodium chloride, 7,2 g/l.
7.2.1.4 Ammonium chloride, 11,0 g/l.
7.2.1.5 Trisodium citrate dihydrate, 1,1 g/l.
7.2.1.6 Lactic acid solution, 3,5 g/l.
7.2.2 Stock Solution B
7.2.2.1 Urea, 5,0 g/l.
7.2.2.2 Uric acid, 0,375 g/l.
7.2.2.3 Sodium hydroxide, 0,1 g/l.
7.2.3 Stock Solution C
7.2.3.1 Potass
...

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