EN 71-11:2005
(Main)Safety of toys - Part 11: Organic chemical compounds - Methods of analysis
Safety of toys - Part 11: Organic chemical compounds - Methods of analysis
This Part 11 of the European Standard EN 71 for safety of toys specifies methods for the analysis of toy and toy material extracts prepared according to the sampling procedures in EN 71-10, to enable assessment of compliance with the chemical requirements specified in EN 71-9.
This European Standard specifies analytical methods for the identification and determination of the following groups of organic chemicals:
Flame retardants
Colourants
Primary aromatic amines
Monomers and solvents
Wood preservatives
Preservatives
Plasticisers
NOTE 1 Methods for formaldehyde in accessible textile components of toys; accessible paper components of toys; and accessible resin-bonded wood components of toys are specified in EN 71-9.
NOTE 2 The method for free formaldehyde as a preservative is specified in EN 71-10.
Sicherheit von Spielzeug - Teil 11: Organisch-chemische Verbindungen, Analysenverfahren
Dieser Teil 11 der Europäischen Norm EN 71 zur Sicherheit von Spielzeug legt Verfahren für die Analyse von Spielzeug- und Spielzeugmaterialextrakten fest, die nach den Probenahmeverfahren in EN 71-10 hergestellt wurden, um die Bewertung der Übereinstimmung mit den in EN 71-9 festgelegten chemischen Anforderungen zu ermöglichen.
Diese Norm legt Analysenverfahren zur qualitativen und quantitativen Bestimmung der folgenden Gruppen organischer Chemikalien fest:
- Flammschutzmittel (Flammverzögerungsmittel);
- Farbstoffe;
- primäre aromatische Amine;
- nicht-flüchtige Monomere und Lösemittel;
- flüchtige Monomere und Lösemittel;
- Holzschutzmittel;
- Konservierungsstoffe;
- Weichmacher.
ANMERKUNG 1 Verfahren für die qualitative und quantitative Bestimmung von Formaldehyd in zugänglichen textilen Bestandteilen von Spielzeug, zugänglichen Bestandteilen aus Papier und harzgebundenen Holzteilen von Spielzeug sind in EN 71-9 festgelegt.
ANMERKUNG 2 Das Verfahren für die Bestimmung von freiem Formaldehyd als Konservierungsstoff ist in EN 71-10 festgelegt.
Sécurité des jouets - Partie 11 : Composés organiques chimiques - Méthodes d'analyse
La présente partie 11 de la Norme européenne EN 71 relative à la sécurité des jouets spécifie des méthodes d’analyse des extraits de jouets et de matériaux jouets préparés selon les procédures d’échantillonnage de l’EN 71-10 pour permettre d’évaluer la conformité avec les exigences chimiques spécifiées dans l’EN 71-9.
La présente Norme européenne spécifie des méthodes d’analyse destinées à l’identification et au dosage des groupes suivants de produits chimiques organiques :
retardateurs de flamme ;
colorants ;
amines aromatiques primaires ;
monomères et solvants ;
produits de préservation du bois ;
agents de conservation ;
plastifiants.
NOTE 1 Les méthodes applicables au formaldéhyde dans les parties textile, papier, en bois stratifié avec résine, accessibles de jouets, sont spécifiées dans l'EN 71-9.
NOTE 2 La méthode applicable au formaldéhyde libre en tant que conservateur est spécifiée dans l'EN 71-10.
Varnost igrač – 11. del: Organske kemijske spojine – Analizne metode
General Information
Standards Content (Sample)
SLOVENSKI STANDARD
01-februar-2006
9DUQRVWLJUDþ±GHO2UJDQVNHNHPLMVNHVSRMLQH±$QDOL]QHPHWRGH
Safety of toys - Part 11: Organic chemical compounds - Methods of analysis
Sicherheit von Spielzeug - Teil 11: Organisch-chemische Verbindungen,
Analysenverfahren
Sécurité des jouets - Partie 11 : Composés organiques chimiques - Méthodes d'analyse
Ta slovenski standard je istoveten z: EN 71-11:2005
ICS:
97.200.50 ,JUDþH Toys
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.
EUROPEAN STANDARD
EN 71-11
NORME EUROPÉENNE
EUROPÄISCHE NORM
November 2005
ICS 97.200.50
English Version
Safety of toys - Part 11: Organic chemical compounds - Methods
of analysis
Sécurité des jouets - Partie 11 : Composés chimiques Sicherheit von Spielzeug - Teil 11: Organisch-chemische
organiques dans les jouets - Méthodes d'analyse Verbindungen - Analysenverfahren
This European Standard was approved by CEN on 27 June 2005.
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 Central Secretariat 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 Central Secretariat has the same status as the official
versions.
CEN members are the national standards bodies of Austria, Belgium, Cyprus, Czech Republic, Denmark, Estonia, Finland, France,
Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Slovakia,
Slovenia, Spain, Sweden, Switzerland and United Kingdom.
EUROPEAN COMMITTEE FOR STANDARDIZATION
COMITÉ EUROPÉEN DE NORMALISATION
EUROPÄISCHES KOMITEE FÜR NORMUNG
Management Centre: rue de Stassart, 36 B-1050 Brussels
© 2005 CEN All rights of exploitation in any form and by any means reserved Ref. No. EN 71-11:2005: E
worldwide for CEN national Members.
Contents
Page
Foreword .3
Introduction.4
1 Scope .5
2 Normative references .5
3 Terms and definitions.5
4 Environmental, health and safety precautions .6
5 Methods of analysis.6
5.1 General .6
5.2 Flame retardants .6
5.3 Colourants.9
5.4 Primary aromatic amines.15
5.5 Monomers and solvents .19
5.6 Wood preservatives.37
5.7 Preservatives.41
5.8 Plasticisers.44
Annex A (informative) Methods of analysis for volatile solvents .48
Annex B (informative) Validation of test methods .65
Annex C (informative) Colourants – conformational analysis .66
Annex ZA (informative) Clauses of this European Standard addressing essential requirements or
other provisions of EU Directives.68
Bibliography.69
Foreword
This European Standard (EN 71-11:2005) has been prepared by Technical Committee CEN/TC 52 “Safety of
Toys”, the secretariat of which is held by DS.
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 May 2006, and conflicting national standards shall be withdrawn at the
latest by May 2006.
This European Standard has been prepared under a mandate given to CEN by the European Commission
and the European Free Trade Association, and supports essential requirements of EU Directive(s).
For relationship with EU Directive(s), see informative Annex ZA, which is an integral part of this European
Standard.
This European Standard constitutes part 11 of the European Standard on Safety of Toys.
This part should be read in conjunction with parts 9 and 10.
According to the CEN/CENELEC Internal Regulations, the national standards organizations of the following
countries are bound to implement this European Standard: Austria, Belgium, Cyprus, Czech Republic,
Denmark, Estonia, Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania,
Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Slovakia, Slovenia, Spain, Sweden, Switzerland
and United Kingdom.
Introduction
The European Standard EN 71 for “safety of toys” consists of the following parts:
Part 1: Mechanical and physical properties
Part 2: Flammability
Part 3: Migration of certain elements
Part 4: Experimental sets for chemistry and related activities
Part 5: Chemical toys (sets) other than experimental sets
Part 6: Graphical symbols for age warning labelling
Part 7: Finger paints – Requirements and test methods
Part 8: Swings, slides and similar activity toys for indoor and outdoor family domestic use
Part 9: Organic chemical compounds – Requirements
Part 10: Organic chemical compounds – Sample preparation and extraction
Part 11: Organic chemical compounds – Methods of analysis
The European Standards EN 71-9, EN 71-10 and EN 71-11 were mandated by the European Commission
(M/229) to address the risks presented by organic chemical compounds in toys by taking into account the
potential exposure and toxicological effects of those substances considered to present the greatest risk to
health.
This European Standard specifies methods of analysis to enable assessment of compliance with the chemical
requirements specified in EN 71-9 when toy and toy material extracts have been prepared according to the
sampling procedures in EN 71-10.
This part on methods of analysis should be read in conjunction with EN 71-9, which contains requirements for
certain organic chemical compounds in toys, and EN 71-10, which describes sample preparation and
extraction procedures.
This European Standard takes into account the opinion of the Toxicology Section of the Scientific Advisory
Committee published in 1992 (EUR 13976), which recommended that certain groups of chemical compounds
used in toys and toy materials need to be given special attention. In drafting this European Standard CEN/TC
52 has considered organic chemicals that can be classified within the following groups:
Solvents
Preservatives
Plasticisers (excluding phthalate plasticisers)
Flame retardants
Monomers
Biocides (wood preservatives)
Processing aids
Colouring agents
Phthalate plasticisers were specifically excluded from the scope of mandate M/229.
1 Scope
This Part 11 of the European Standard EN 71 for safety of toys specifies methods for the analysis of toy and
toy material extracts prepared according to the sampling procedures in EN 71-10, to enable assessment of
compliance with the chemical requirements specified in EN 71-9.
This European Standard specifies analytical methods for the identification and determination of the following
groups of organic chemicals:
Flame retardants
Colourants
Primary aromatic amines
Monomers and solvents
Wood preservatives
Preservatives
Plasticisers
NOTE 1 Methods for formaldehyde in accessible textile components of toys; accessible paper components of toys; and
accessible resin-bonded wood components of toys are specified in EN 71-9.
NOTE 2 The method for free formaldehyde as a preservative is specified in EN 71-10.
2 Normative references
The following referenced documents are indispensable for the application of this European Standard. For
dated references, only the edition cited applies. For undated references, the latest edition of the referenced
document (including any amendments) applies.
EN 71-9:2005, Safety of toys – Part 9: Organic chemical compounds – Requirements
EN 71-10:2005, Safety of toys – Part 10: Organic chemical compounds – Sample preparation and extraction
EN ISO 3696, Water for analytical laboratory use – Specification and test methods (ISO 3696:1987)
3 Terms and definitions
For the purposes of this European Standard, the following terms and definitions apply.
3.1
action limit
routinely-achievable limit of quantification for a particular substance using the specified method of analysis
3.2
aqueous migrate
liquid obtained after extracting a toy material according to the procedure specified in Clause 6 of EN 71-
10:2005
3.3
test portion
portion of the laboratory sample prepared for analysis
3.4
toy material
material from which toys and toy components are made
NOTE This definition differs from that given in EN 71-3
4 Environmental, health and safety precautions
When preparing this European Standard, consideration was given to the minimisation of environmental
impacts caused by the use of the methods of analysis.
It is the users’ responsibility to use safe and proper techniques in handling materials in the methods of
analysis specified in this European Standard.
Consult manufacturers for specific details such as material safety data sheets and other
recommendations.
Wear protective goggles and coats in all laboratory areas.
Be careful about substances, which are toxic and/or human carcinogens.
A fume cupboard shall be used during preparation of organic solvent solutions.
Solvents shall be disposed of in accordance with environmental requirements.
5 Methods of analysis
5.1 General
All chemicals used for analysis shall be of analytical grade (pro analysis) or, if unavailable, the best technical
grade. Water shall be of grade 3 according to EN ISO 3696 or of a comparable quality, and demonstrably free
from analytes of interest.
The precision of volumetric glassware should be grade A.
The analysis of toys and toy materials for chemical compounds for which limits are given in Tables 2 A to 2 I
of EN 71-9:2005 shall be performed in accordance with the sampling procedures specified in EN 71-10 and
the methods of analysis described in this European Standard. Alternative methods of analysis are acceptable
only if they are capable of achieving at least the accuracy and precision of the methods described in this
European Standard; an adequate sensitivity; and have been validated to show that the results are equivalent
to those of these standard methods.
5.2 Flame retardants
NOTE Methods are given for pentabromodiphenyl ether and octabromodiphenyl ether in order to enable compliance
with Directive 2003/11/EC of the European Parliament and of the Council to be demonstrated for textile toy materials.
5.2.1 Principle
Flame retardants are determined in acetonitrile extracts of toy materials by liquid chromatography with diode-
array and mass spectrometry detection (LC-DAD-MS) using the external standard method of calibration.
5.2.2 Standards, reagents and solvents
5.2.2.1 Standards
2*
5.2.2.1.1 Pentabromodiphenyl ether , CAS No. 32534-81-9
5.2.2.1.2 Octabromodiphenyl ether * , CAS No. 32536-52-0
5.2.2.1.3 Tri-o-cresyl phosphate, CAS No. 78-30-8
5.2.2.1.4 Tris(2-chloroethyl) phosphate, CAS No. 115-96-8
5.2.2.2 Reagents and solvents
5.2.2.2.1 Acetonitrile
5.2.2.2.2 Dichloromethane
5.2.2.2.3 Ammonium acetate, anhydrous
5.2.2.2.4 Acetic acid, glacial
5.2.2.2.5 Ammonium acetate, 10 mmol/l aqueous solution, pH 3,6
Transfer (0,77 0,01) g ammonium acetate (5.2.2.2.3) into a 1 000-ml volumetric flask, add 980 ml of water,
±
adjust the pH to 3,6 ± 0,1 with glacial acetic acid and make up to the mark with water.
5.2.2.3 Stock standard solution (100 mg/l)
Weigh, to the nearest 0,1 mg, (10 ± 1) mg of each flame retardant (5.2.2.1) into a 100-ml volumetric flask.
Add 25 ml of acetonitrile (5.2.2.2.1) and mix carefully to dissolve. Place in an ultrasonic bath for 10 min to
ensure complete dissolution. Make up to the mark with acetonitrile.
The stability of the mixed stock standard solution should be checked regularly
...
SLOVENSKI STANDARD
01-februar-2006
Varnost igrač – 11. del: Organske kemijske spojine – Analizne metode
Safety of toys - Part 11: Organic chemical compounds - Methods of analysis
Sicherheit von Spielzeug - Teil 11: Organisch-chemische Verbindungen,
Analysenverfahren
Sécurité des jouets - Partie 11 : Composés organiques chimiques - Méthodes d'analyse
Ta slovenski standard je istoveten z: EN 71-11:2005
ICS:
97.200.50 Igrače Toys
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.
EUROPEAN STANDARD
EN 71-11
NORME EUROPÉENNE
EUROPÄISCHE NORM
November 2005
ICS 97.200.50
English Version
Safety of toys - Part 11: Organic chemical compounds - Methods
of analysis
Sécurité des jouets - Partie 11 : Composés chimiques Sicherheit von Spielzeug - Teil 11: Organisch-chemische
organiques dans les jouets - Méthodes d'analyse Verbindungen - Analysenverfahren
This European Standard was approved by CEN on 27 June 2005.
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 Central Secretariat 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 Central Secretariat has the same status as the official
versions.
CEN members are the national standards bodies of Austria, Belgium, Cyprus, Czech Republic, Denmark, Estonia, Finland, France,
Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Slovakia,
Slovenia, Spain, Sweden, Switzerland and United Kingdom.
EUROPEAN COMMITTEE FOR STANDARDIZATION
COMITÉ EUROPÉEN DE NORMALISATION
EUROPÄISCHES KOMITEE FÜR NORMUNG
Management Centre: rue de Stassart, 36 B-1050 Brussels
© 2005 CEN All rights of exploitation in any form and by any means reserved Ref. No. EN 71-11:2005: E
worldwide for CEN national Members.
Contents
Page
Foreword .3
Introduction.4
1 Scope .5
2 Normative references .5
3 Terms and definitions.5
4 Environmental, health and safety precautions .6
5 Methods of analysis.6
5.1 General .6
5.2 Flame retardants .6
5.3 Colourants.9
5.4 Primary aromatic amines.15
5.5 Monomers and solvents .19
5.6 Wood preservatives.37
5.7 Preservatives.41
5.8 Plasticisers.44
Annex A (informative) Methods of analysis for volatile solvents .48
Annex B (informative) Validation of test methods .65
Annex C (informative) Colourants – conformational analysis .66
Annex ZA (informative) Clauses of this European Standard addressing essential requirements or
other provisions of EU Directives.68
Bibliography.69
Foreword
This European Standard (EN 71-11:2005) has been prepared by Technical Committee CEN/TC 52 “Safety of
Toys”, the secretariat of which is held by DS.
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 May 2006, and conflicting national standards shall be withdrawn at the
latest by May 2006.
This European Standard has been prepared under a mandate given to CEN by the European Commission
and the European Free Trade Association, and supports essential requirements of EU Directive(s).
For relationship with EU Directive(s), see informative Annex ZA, which is an integral part of this European
Standard.
This European Standard constitutes part 11 of the European Standard on Safety of Toys.
This part should be read in conjunction with parts 9 and 10.
According to the CEN/CENELEC Internal Regulations, the national standards organizations of the following
countries are bound to implement this European Standard: Austria, Belgium, Cyprus, Czech Republic,
Denmark, Estonia, Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania,
Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Slovakia, Slovenia, Spain, Sweden, Switzerland
and United Kingdom.
Introduction
The European Standard EN 71 for “safety of toys” consists of the following parts:
Part 1: Mechanical and physical properties
Part 2: Flammability
Part 3: Migration of certain elements
Part 4: Experimental sets for chemistry and related activities
Part 5: Chemical toys (sets) other than experimental sets
Part 6: Graphical symbols for age warning labelling
Part 7: Finger paints – Requirements and test methods
Part 8: Swings, slides and similar activity toys for indoor and outdoor family domestic use
Part 9: Organic chemical compounds – Requirements
Part 10: Organic chemical compounds – Sample preparation and extraction
Part 11: Organic chemical compounds – Methods of analysis
The European Standards EN 71-9, EN 71-10 and EN 71-11 were mandated by the European Commission
(M/229) to address the risks presented by organic chemical compounds in toys by taking into account the
potential exposure and toxicological effects of those substances considered to present the greatest risk to
health.
This European Standard specifies methods of analysis to enable assessment of compliance with the chemical
requirements specified in EN 71-9 when toy and toy material extracts have been prepared according to the
sampling procedures in EN 71-10.
This part on methods of analysis should be read in conjunction with EN 71-9, which contains requirements for
certain organic chemical compounds in toys, and EN 71-10, which describes sample preparation and
extraction procedures.
This European Standard takes into account the opinion of the Toxicology Section of the Scientific Advisory
Committee published in 1992 (EUR 13976), which recommended that certain groups of chemical compounds
used in toys and toy materials need to be given special attention. In drafting this European Standard CEN/TC
52 has considered organic chemicals that can be classified within the following groups:
Solvents
Preservatives
Plasticisers (excluding phthalate plasticisers)
Flame retardants
Monomers
Biocides (wood preservatives)
Processing aids
Colouring agents
Phthalate plasticisers were specifically excluded from the scope of mandate M/229.
1 Scope
This Part 11 of the European Standard EN 71 for safety of toys specifies methods for the analysis of toy and
toy material extracts prepared according to the sampling procedures in EN 71-10, to enable assessment of
compliance with the chemical requirements specified in EN 71-9.
This European Standard specifies analytical methods for the identification and determination of the following
groups of organic chemicals:
Flame retardants
Colourants
Primary aromatic amines
Monomers and solvents
Wood preservatives
Preservatives
Plasticisers
NOTE 1 Methods for formaldehyde in accessible textile components of toys; accessible paper components of toys; and
accessible resin-bonded wood components of toys are specified in EN 71-9.
NOTE 2 The method for free formaldehyde as a preservative is specified in EN 71-10.
2 Normative references
The following referenced documents are indispensable for the application of this European Standard. For
dated references, only the edition cited applies. For undated references, the latest edition of the referenced
document (including any amendments) applies.
EN 71-9:2005, Safety of toys – Part 9: Organic chemical compounds – Requirements
EN 71-10:2005, Safety of toys – Part 10: Organic chemical compounds – Sample preparation and extraction
EN ISO 3696, Water for analytical laboratory use – Specification and test methods (ISO 3696:1987)
3 Terms and definitions
For the purposes of this European Standard, the following terms and definitions apply.
3.1
action limit
routinely-achievable limit of quantification for a particular substance using the specified method of analysis
3.2
aqueous migrate
liquid obtained after extracting a toy material according to the procedure specified in Clause 6 of EN 71-
10:2005
3.3
test portion
portion of the laboratory sample prepared for analysis
3.4
toy material
material from which toys and toy components are made
NOTE This definition differs from that given in EN 71-3
4 Environmental, health and safety precautions
When preparing this European Standard, consideration was given to the minimisation of environmental
impacts caused by the use of the methods of analysis.
It is the users’ responsibility to use safe and proper techniques in handling materials in the methods of
analysis specified in this European Standard.
Consult manufacturers for specific details such as material safety data sheets and other
recommendations.
Wear protective goggles and coats in all laboratory areas.
Be careful about substances, which are toxic and/or human carcinogens.
A fume cupboard shall be used during preparation of organic solvent solutions.
Solvents shall be disposed of in accordance with environmental requirements.
5 Methods of analysis
5.1 General
All chemicals used for analysis shall be of analytical grade (pro analysis) or, if unavailable, the best technical
grade. Water shall be of grade 3 according to EN ISO 3696 or of a comparable quality, and demonstrably free
from analytes of interest.
The precision of volumetric glassware should be grade A.
The analysis of toys and toy materials for chemical compounds for which limits are given in Tables 2 A to 2 I
of EN 71-9:2005 shall be performed in accordance with the sampling procedures specified in EN 71-10 and
the methods of analysis described in this European Standard. Alternative methods of analysis are acceptable
only if they are capable of achieving at least the accuracy and precision of the methods described in this
European Standard; an adequate sensitivity; and have been validated to show that the results are equivalent
to those of these standard methods.
5.2 Flame retardants
NOTE Methods are given for pentabromodiphenyl ether and octabromodiphenyl ether in order to enable compliance
with Directive 2003/11/EC of the European Parliament and of the Council to be demonstrated for textile toy materials.
5.2.1 Principle
Flame retardants are determined in acetonitrile extracts of toy materials by liquid chromatography with diode-
array and mass spectrometry detection (LC-DAD-MS) using the external standard method of calibration.
5.2.2 Standards, reagents and solvents
5.2.2.1 Standards
2*
5.2.2.1.1 Pentabromodiphenyl ether , CAS No. 32534-81-9
5.2.2.1.2 Octabromodiphenyl ether * , CAS No. 32536-52-0
5.2.2.1.3 Tri-o-cresyl phosphate, CAS No. 78-30-8
5.2.2.1.4 Tris(2-chloroethyl) phosphate, CAS No. 115-96-8
5.2.2.2 Reagents and solvents
5.2.2.2.1 Acetonitrile
5.2.2.2.2 Dichloromethane
5.2.2.2.3 Ammonium acetate, anhydrous
5.2.2.2.4 Acetic acid, glacial
5.2.2.2.5 Ammonium acetate, 10 mmol/l aqueous solution, pH 3,6
Transfer (0,77 0,01) g ammonium acetate (5.2.2.2.3) into a 1 000-ml volumetric flask, add 980 ml of water,
±
adjust the pH to 3,6 ± 0,1 with glacial acetic acid and make up to the mark with water.
5.2.2.3 Stock standard solution (100 mg/l)
Weigh, to the nearest 0,1 mg, (10 ± 1) mg of each flame retardant (5.2.2.1) into a 100-ml volumetric flask.
Add 25 ml of acetonitrile (5.2.2.2.1) and mix carefully to dissolve. Place in an ultrasonic bath for 10 min to
ensure complete dissolution. Make up to the mark with acetonitrile.
The stability of the mixed stock standard solution should be checked regularly. It should be
...
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