ISO 6923:2023

Paints and varnishes — Determination of monomeric diisocyanate content in coating materials and similar products using high performance liquid chromatography with ultraviolet detection (HPLC-UV)

This document specifies a method for the quantitative determination of monomeric diisocyanate content in coating materials, adhesives and other liquid or pasty materials. This method is suitable for the quantification of the following monomeric diisocyanates: methylene diphenyl diisocyanate (MDI, 2,4’-MDI and 4,4’-MDI), toluene diisocyanate (TDI, 2,6-TDI, 2,4-TDI), (cis/trans) isophorone diisocyanate (IPDI) and hexamethylene diisocyanate (HDI,1,6-HDI) in various matrices for concentrations ranging from 0,01 % to 2,0 % mass fraction. For higher concentrations, a suitable dilution before the derivatization with p-nitrobenzyl-N-propylamine (PNBPA) is performed. The measurements are carried out using ultra high performance liquid chromatography (UHPLC) with a multiple wavelength detector.

Peintures et vernis — Dosage des diisocyanates monomères dans les produits de peinture et produits similaires par chromatographie en phase liquide haute performance couplée à un détecteur ultraviolet (HPLC-UV)

Le présent document spécifie une méthode de dosage quantitatif des diisocyanates monomères dans les produits de peinture, les adhésifs et autres matériaux liquides ou pâteux. La présente méthode est applicable à la quantification des diisocyanates monomères suivants: le diisocyanate de diphénylméthylène (MDI, 2,4’-MDI et 4,4’-MDI), le diisocyanate de toluène (TDI, 2,6-TDI, 2,4-TDI), le diisocyanate d’isophorone (IPDI) (cis/trans) et le diisocyanate d’hexaméthylène (HDI, 1,6-HDI) présents dans différentes matrices à des concentrations comprises entre 0,01 % et 2,0 % en fraction massique. Pour les concentrations plus élevées, une dilution appropriée précède la dérivatisation à la p-nitrobenzyle-N-propylamine (PNBPA). Les mesurages sont réalisés par chromatographie en phase liquide ultra-haute performance (UHPLC) avec un détecteur à longueurs d’ondes multiples.

General Information

• Status: Published
• Publication Date: 04-Sep-2023
• ICS: 87.040 - Paints and varnishes
• Technical Committee: ISO/TC 35/SC 16 - Chemical analysis
• Drafting Committee: ISO/TC 35/SC 16 - Chemical analysis
• Current Stage: 6060 - International Standard published
• Start Date: 05-Sep-2023
• Due Date: 11-May-2024
• Completion Date: 05-Sep-2023

Standards Content (Sample)

INTERNATIONAL ISO
STANDARD 6923
First edition
2023-09
Paints and varnishes — Determination
of monomeric diisocyanate content in
coating materials and similar products
using high performance liquid
chromatography with ultraviolet
detection (HPLC-UV)
Reference number
© ISO 2023
All rights reserved. Unless otherwise specified, or required in the context of its implementation, no part of this publication may
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ii
Contents Page
Foreword .iv
Introduction .v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Principle . 1
5 Apparatus . 1
6 Reagents . 3
7 Reference standards . 4
8 Sampling . 4
9 Procedure .4
9.1 Sample preparation . 4
9.2 Calibration . 5
9.2.1 Preparation of the standard . 5
9.2.2 Quantification . 5
10 Calculation . 7
11 Expression of results . 8
12 Test report . 8
Annex A (informative) Details of validation. 9
Bibliography .10
iii
Foreword
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This document was prepared by Technical Committee ISO/TC 35, Paints and varnishes, Subcommittee
SC 16, Chemical analysis.
Any feedback or questions on this document should be directed to the user’s national standards body. A
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iv
Introduction
The analytical method described in this document was developed in 2011. The validity of this method
has been continuously tested until it was finalized in 2015 for the low content monomer diisocyanate
under 0,20 % mass fraction. Several internal interlaboratory tests have clearly demonstrated its
reproducibility. Moreover, under the framework of interlaboratory tests organized by the Association
of the European Adhesive and Sealant Industry (FEICA), it has been shown that the described method is
accurate in determining monomer diisocyanate content in various polyurethane (PU) matrices.
v
INTERNATIONAL STANDARD ISO 6923:2023(E)
Paints and varnishes — Determination of monomeric
diisocyanate content in coating materials and similar
products using high performance liquid chromatography
with ultraviolet detection (HPLC-UV)
1 Scope
This document specifies a method for the quantitative determination of monomeric diisocyanate
content in coating materials, adhesives and other liquid or pasty materials.
This method is suitable for the quantification of the following monomeric diisocyanates: methylene
diphenyl diisocyanate (MDI, 2,4’-MDI and 4,4’-MDI), toluene diisocyanate (TDI, 2,6-TDI, 2,4-TDI), (cis/
trans) isophorone diisocyanate (IPDI) and hexamethylene diisocyanate (HDI,1,6-HDI) in various
matrices for concentrations ranging from 0,01 % to 2,0 % mass fraction. For higher concentrations, a
suitable dilution before the derivatization with p-nitrobenzyl-N-propylamine (PNBPA) is performed.
The measurements are carried out using ultra high performance liquid chromatography (UHPLC) with
a multiple wavelength detector.
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 4618, Paints and varnishes — Vocabulary
ISO 15528, Paints, varnishes and raw materials for paints and varnishes — Sampling
3 Terms and definitions
For the purposes of this document, the terms and definitions given in ISO 4618 apply.
ISO and IEC maintain terminology databases for use in standardization at the following addresses:
— ISO Online browsing platform: available at https:// www .iso .org/ obp
— IEC Electropedia: available at https:// www .electropedia .org/
4 Principle
The sample is directly weighed into a 10 ml measuring flask (the mass depends on the isocyanate
content). The flask is filled with dry acetonitrile to the mark. Subsequently, in a vial, an aliquot of the
solution is derivatised with PNBPA in dry acetonitrile (1+1 by volume). After filtration, the clear solution
is injected directly into the HPLC.
5 Apparatus
Use ordinary laboratory apparatus and glassware together with the following.
5.1 HPLC/UV with the parameters given in Table 1.
Table 1 — Parameters
b
System HPLC system with a pressure up to 600 bar and a quaternary gradient pump, including a
thermostat oven
Detector Multiple wavelength detector
Column HPLC column superficial porous particles, C18 100 Å, particle size 2,6 µm, column dimension
TMa
100 x 3 mm, e.g. Kinetex
Column oven (30 ± 1) °C
Mobile phase A 40 mM sodium acetate (pH 4,5)
Mobile phase B fresh deionised water
Mobile phase C acetonitrile
Gradient
Time A % B % C %
(min)
−4,00 55 0 45
0,00 55 0 45
3,25 45 0 55
5,70 35 0 65
5,80 0 35 65
6,00 0 35 65
7,00 0 5 95
10,00 0 5 95
Flow rate 1,40 ml/min
Detection UV 275 nm 2,6-TDI, 2,4-TDI, c/t-IPDI, 1,6-HDI
UV 250 nm 2,4’-MDI; 4,4’-MDI
Injection volume 2,5 µl
a
Kinetex is the trade name of a product supplied by Phenomenex. This information is given for the convenience of users
of this document and does not constitute an endorsement by ISO of the product named. Equivalent products may be used if
they can be shown to lead to the same results.
b 5 2
1 bar = 0,1 MPa = 10 Pa; 1 MPa = 1 N/mm .
5.2 Balance
In the 60 g range, expect readability of 0,01 mg, repeatability of 0,015 mg, and linearity of ±0,08 mg.
5.3 Filter system, filtration glassware
5.4 Filter membranes, nylon, 0,20 µm pore size, 47 mm diameter.
5.5 Pipette, of capacity 200 µl, 1 000 µl and 10 000 µl.
5.6 Measuring flask, of capacity 10 ml.
5.7 Pipette tips, polypropylene, tip-rack, 50 µl to 1 000 µl.
5.8 Derivatisation vials, of capacity 5 ml with PE-lid.
5.9 HPLC vials, of capacity 2 ml.
5.10 Syringe filter, 0,2 µm syringe filter polyamide PA 66.
5.11 One-way syringe, of capacity 1 ml.
6 Reagents
6.1 Acetonitrile, HPLC, >99,9 % UV grade, dried over molecular sieve.
6.2 Deionised water, resistance >18 MΩ.
6.3 4-Nitro-N-propylbenzylamin-hydrochloride (PNBPA-HCl)
6.4 Petrol ether, 50 °C to 70 °C.
6.5 Sodium hydroxide pellets
6.6 Magnesium sulfate
6.7 Sodium acetate, water free, 99 % puriss.
6.8 Molecular sieves, 4 Å.
6.9 Mobile phase C: acetonitrile, gradient grade for liquid chromatography.
6.10 Sulfuric acid, c = 1 mol/l.
Fill a 500 ml measuring flask with 250 ml deionized water and add 27,5 ml concentrated sulfuric acid
(97 %).
Complete the measuring flask with deionized water to the mark.
6.11 Mobile phase A: 40 mM sodium acetate, pH ~4,5.
Weigh 6,63 g of sodium acetate water free (99 %) in a 2 l Erlenmeyer flask.
Add 2 l of deionized water and 13 ml of H SO , c = 1 mol/l.
2 4
6.12 Derivatisation agent (PNBPA)
Weigh about 1,0 g PNBPA-HCl in an erlenmeyer flask and dissolve in 40 ml deionised water.
Add drop wise a solution of 2 N sodium hydroxide (about 30 drops). The solution will become milky.
Extract three times with 20 ml petrol ether (50 °C to 70 °C) in a separating funnel.
Dry the petrol ether phase over magnesium sulfate for 15 min.
Filter the petrol ether phase into a round bottomed flask.
Concentrate the solution in the rotary evaporator at 40 °C until a light-yellow oil is obtained.
Take up the yellow residue with 150 ml dry acetonitrile into a brown bottle filled with a molecular
sieve.
Store the solution in the fridge for no more than two months at a temperature of less than or equal to
4 °C before use.
7 Reference standards
7.1 2,4’-/4,4’-Methylene diphenyl diisocyanates, ratio: 2,4’ (51 %)/ 4,4’ (49 %), purity at least
99,4 % (mass fraction) determined in accordance with this document using a standard 4,4'-MDI of at
least 99,5 % (mas
...