oSIST ISO/FDIS 16702:2026

International
Standard
ISO 16702
Third edition
Workplace air — Determination
2026-07
of total organic isocyanate groups
in air using 1-(2-methoxyphenyl)
piperazine and liquid
chromatography
Air des lieux de travail — Dosage des groupements isocyanates
organiques totaux dans l'air par dérivatisation avec la
1-(2-méthoxyphényl)pipérazine et par chromatographie en phase
liquide
Reference number
© ISO 2026
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Published in Switzerland
ii
Contents Page
Foreword .v
Introduction .vi
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Principle . 2
5 Reagents . 3
6 Apparatus . 3
7 Reagent and calibration solutions . 5
7.1 Reagent solutions .5
7.1.1 Absorbing solution .5
7.1.2 Preparation of solution for impregnating filters (solution A) .5
7.1.3 Stability of reagent solutions .5
7.2 Calibration standards .5
7.2.1 Preparation of monomer derivatives .5
7.2.2 Alternative procedure for the less soluble isocyanate derivatives .5
7.2.3 Preparation of standard solutions of recrystallised isocyanate monomer
derivatives .5
7.2.4 Stability of isocyanate ureas and their solutions .6
7.3 HPLC mobile phase .6
7.3.1 General .6
7.3.2 Preparation of “slow” mobile phase .6
7.3.3 Preparation of “fast” mobile phase .6
7.4 Calibration blend atmosphere .6
8 Sampling . 7
8.1 Calibration of pump .7
8.2 Sampling duration .7
8.3 Preparation of sampling equipment .7
8.3.1 General .7
8.3.2 Preparation of impregnated filters .7
8.3.3 Preparation of sampling devices (filters) .7
8.3.4 Preparation of impingers .7
8.4 Collection of filter samples (vapour phase samples) .7
8.4.1 Set-up of filter samplers .7
8.4.2 Collection of filter samples .8
8.5 Collection of impinger backed by filter samples (isocyanate aerosols) .8
8.5.1 Rationale for impinger backed by filter sampling .8
8.5.2 Recommended sampling rate for impinger backed by filter .8
8.6 Measurements to be made at the end of the sampling period .8
8.7 Sample logging and field desorption of samples .8
8.8 Transportation .9
8.8.1 Transportation of filter samples .9
8.8.2 Transportation of impinger samples .9
8.9 Field blanks.9
9 Analytical methods . 9
9.1 Safety precautions .9
9.2 Cleaning of glassware.9
9.3 Prereaction of impinger samples before HPLC analysis .9
9.4 Prereaction of filter samples before HPLC analysis .9
9.5 HPLC conditions .10
9.5.1 Choice of HPLC conditions .10

iii
9.5.2 Optimising the HPLC analysis .10
9.6 Determination of airborne isocyanate for monomeric isocyanates (UV detection) .11
9.7 Identification of polymeric isocyanates: EC:UV ratio approach .11
9.8 Confirmation of identification for polymeric isocyanates . 12
9.8.1 Analysis of a bulk sample . 12
9.8.2 Confirmation of identity using a diode array detector . 12
9.8.3 Confirmation of identity using other techniques . 12
9.9 Quantification of airborne isocyanate for polymeric isocyanates (EC detection) . 13
9.10 Sampling efficiency. 13
10 Calculations .13
11 Interferences . 14
12 Uncertainty of measurement . 14
12.1 Overview .14
12.1.1 General .14
12.1.2 Summary of approach .14
12.1.3 Summary of calculated uncertainty data .14
12.2 Assessment of performance characteristics of the method — Sampling considerations
(detailed ISO/IEC Guide 98-3:2008 approach) . 15
12.2.1 Collection efficiency relative to particle size distribution . 15
12.2.2 Sampled volume of air . 15
12.2.3 Sampling time . 15
12.2.4 Variations in flow rate during sampling .16
12.2.5 Concentration conversion to other specified temperature and pressure
conditions .16
12.2.6 Combined uncertainty of sample volume .16
12.3 Assessment of performance characteristics of the method — Other considerations
(detailed approach) .17
12.3.1 Mass of compound in sample . .17
12.3.2 Analyte stability .17
12.3.3 Reaction and extraction efficiency .17
12.3.4 Uncorrected analytical mass of compound .18
12.3.5 Calibration standards .18
12.3.6 Lack-of-fit of calibration function .19
12.3.7 Drift in detector response . .19
12.3.8 Precision of the analysis .19
12.3.9 Analytical selectivity . 20
12.3.10 Combined uncertainty in the analytical mass of compound . 20
12.3.11 Combined uncertainty in the sampled mass of compound . 20
12.4 Mass of compound in field sample blank. 20
12.5 Between-laboratory uncertainty contributions .21
12.6 Combined uncertainty .21
12.7 Expanded uncertainty .21
13 Stability .21
14 Test report .21
15 Quality control .22
Annex A (informative) Determination of sampling efficiency .23
Annex B (informative) Data used for uncertainty estimates .24
Annex C (informative) Combined uncertainties for isocyanate formulations .25
Annex D (informative) Sample chromatograms .27
Bibliography .32

iv
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).
ISO draws attention to the possibility that the implementation of this document may involve the use of (a)
patent(s). ISO takes no position concerning the evidence, validity or applicability of any claimed patent
rights in respect thereof. As of the date of publication of this document, ISO had not received notice of (a)
patent(s) which may be required to implement this document. However, implementers are cautioned that
this may not represent the latest information, which may be obtained from the patent database available at
www.iso.org/patents. ISO shall not be held responsible for identifying any or all such patent rights.
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 146, Air quality, Subcommittee SC 2, Workplace
atmospheres.
This third edition cancels and replaces the second edition (ISO 16702:2007), which has been technically
revised.
The main changes are as follows:
— the references have been reviewed and updated, and obsolete references have been removed or replaced
where appropriate;
— the Introduction and the Scope have been revised to conform with current ISO editorial requirements
and to improve clarity on the applicability of the method;
— minor technical changes have been made, including the harmonization of common names of chemical
compounds;
— additional information has been added on the use of impingers for sampling isocyanates (Clause 4);
— a note on the requirement to record the final volume of toluene has been introduced (8.8.2);
— examples of suitable internal standards have been added (9.9).
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.

v
Introduction
Isocyanates are organic compounds containing the isocyanate functional group (-NCO) and are
widely used in industrial applications such as the manufacture of polyurethanes, paints, coatings,
foams, plastics and adhesives. They are highly reactive substances and are well-established respiratory
sensitisers, representing a major cause of chemically induced occupational asthma. Occupational exposure
can occur primarily by inhalation and, potentially, by skin contact.
Occupational exposure limits for isocyanates have been established in several countries and are generally
expressed in terms of total isocyanate, defined as the sum of monomeric and polymeric isocyanates, including
oligomeric and prepolymeric forms. These limits are specified as long-term (8 h time-weighted average) and
short-term (15 min) exposure limits and require analytical methods capable of determining total isocyanate
groups in workplace air.
The sampling and analysis of airborne isocyanates present particular challenges due to the diversity
of chemical structures, molecular masses and physical forms encountered in workplace atmospheres.
Isocyanates can be present as vapours, aerosols or liquids and often occur as mixtures of monomers, oligomers
and polymers. Other airborne substances, such as water vapour, dust, amines and alcohols, can also be
present and can interfere with analytical determination. In addition, reference standards for many polymeric
isocyanates are currently not available, despite their contribution to total isocyanate exposure.
Because of the high reactivity of the isocyanate functional group, workplace air monitoring is commonly
based on derivatisation techniques that convert isocyanates into more stable compounds suitable for
analysis. The method described in this document is based on derivatisation with 1-(2-methoxyphenyl)
piperazine (MP), forming stable urea derivatives that are analysed by liquid chromatography with
[1]
electrochemical and ultraviolet and visible detection. The analytical approach was established using
widely used industrial diisocyanates, such as methylene diphenyl diisocyanate (MDI), hexamethylene
diisocyanate (HDI), and toluene diisocyanate (TDI), together with their associated oligomeric and polymeric
forms. It has subsequently been applied to a broader range of organic isocyanates containing free isocyanate
groups e.g. phenylisocyanate (PI), isophoronediisocyante (IPDI), naphthyldiisocyante (NDI), hydrogenated
methylene diphenyl diisocyanate (H12MDI) and butylisocyanate.
If both isocyanates and amines are present and need to be determined, a standard capable of simultaneous
[2]
determination of both classes of compounds can be more appropriate (see ISO 17734-2 ). This method has
[3]
also been modified for the determination of monoisocyanates produced during thermal degradation, for
[4]
the use of mass spectrometric detection, and for alternative sampling equipment, such as 37 mm filters and
other filter holders; however, these modifications are not covered by this document. When using a modified
version of this method, it is the responsibility of the user to demonstrate the validity of the modifications.
Sampling approaches depend on the physical form of the isocyanates present. Filters are suitable for the
collection of vapour-phase isocyanates, while combined impinger and filter arrangements are used for
aerosol sampling. The method has been applied to commonly occurring mono- and diisocyanates and to
polymeric isocyanates derived from these monomers.

vi
International Standard ISO 16702:2026(en)
Workplace air — Determination of total organic isocyanate
groups in air using 1-(2-methoxyphenyl)piperazine and
liquid chromatography
1 Scope
This document specifies a test method for the sampling and analysis of airborne organic isocyanate (NCO)
compounds in workplace air. The method covers organic compounds containing free isocyanate functional
groups, including monomeric, oligomeric, prepolymeric and polymeric isocyanates, and addresses the
measurement of total isocyanate groups in air samples collected for the assessment of occupational
exposure.
The method is suitable for personal air sampling in the breathing zone for the determination of time-weighted
average concentrations over sampling periods ranging from approximately 10 min to 8 h, although it can be
applied to shorter sampling periods with high isocyanate air levels. It can also be used for background or
fixed-location air sampling; however, due to aerodynamic effects, samplers designed for personal sampling
do not necessarily exhibit the same collection characteristics when used for other purposes. It covers the
measurement of airborne organic isocyanates over a concentration range of approximately 0,1 µg/m to
140 µg/m for a nominal air sample volume of 15 l; under the conditions specified in this document, typical
3 3
qualitative and quantitative detection limits correspond to approximately 0,07 µg/m and 0,3 µg/m ,
respectively, for a 15 l air sample.
This document does not apply to the simultaneous determination of isocyanates and amines, nor to modified
methods employing alternative sampling devices or detection techniques not described in this document.
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 3696, Water for analytical laboratory use — Specification and test methods
ISO 5725-2, Accuracy (trueness and precision) of measurement methods and results — Part 2: Basic method for
the determination of repeatability and reproducibility of a standard measurement method
ISO 13137, Workplace atmospheres — Pumps for personal sampling of chemical and biological agents —
Requirements and test methods
ISO 18158, Workplace air — Terminology
EN 1540, Workplace exposure – Terminology
3 Terms and definitions
For the purposes of this document, the terms and definitions given in ISO 18158, EN 1540 and the following
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/

3.1
bulk isocyanate material
isocyanate (3.3) based product supplied in bulk form and used in a manufacturing or processing operation
3.2
diisocyanate
chemical compound with two isocyanate (3.3) functional groups
3.3
isocyanate
chemical compound with one or more isocyanate (nitrogen carbon oxygen) functional groups
3.4
monomer
chemical compound that joins with other identical compounds to form dimers, trimers, oligomers (3.5) or
polymers
Note 1 to entry: Classes of isocyanate monomers include: monoisocyanates, containing one isocyanate functional
group, e.g. methyl isocyanate; diisocyanates (3.2), e.g. di(4-isocyanatophenyl)methane (MDI); and triisocyanates, e.g.
tri(4-isocyanatophenyl)methane.
3.5
oligomer
compound of low relative molecular mass with multiple isocyanate (3.3) functional groups, formed by the
combination of isocyanate monomers (3.4)
3.6
prepolymer
isocyanato-terminated reaction product of a diisocyanate (3.2) or polyisocyanate with a stochiometric
deficiency of a hydroxyl-terminated polyol
Note 1 to entry: When used in the workplace, these prepolymers then react further to form polyurethanes or similar
compounds
3.7
uncertainty
parameter, associated with the result of a measurement, that characterises the dispersion of the values that
can reasonably be attributed to the measurand
Note 1 to entry: The parameter can be, for example, a standard deviation (or a given multiple of it), or the width of a
confidence interval.
Note 2 to entry: Uncertainty of measurement comprises, in general, many components. Some of these components can
be evaluated from the statistical distribution of the results of series of measurements and can be characterised by
standard deviations. The other components, which can also be characterised by standard deviations, are evaluated
from assumed probability distributions based on experience or other information. This is often referred to as type A
and type B evaluations of uncertainty, respectively.
4 Principle
The selection of the sampling arrangement in this method is determined by the physical state of the
isocyanate being monitored. When sampling isocyanate aerosols, air is drawn through a glass impinger
containing a solution of 1-(2-methoxyphenyl)piperazine (MP), followed by an MP-impregnated backup
filter. In contrast, for isocyanates present in the vapour phase, sampling may be carried out using an MP-
impregnated filter alone.
Impingers provide more efficient collection than filters when isocyanates are present in the aerosol phase.
Nevertheless, very fine particles, particularly those smaller than 1 µm, might not be fully retained by an
[5,6] [7]
impinger, and a so a treated downstream filter is required. Sampling methods based solely on filters
can lead to underestimation of exposure where larger particles (greater than 10 µm) are present or under

[8]
conditions of high aerosol loading, as the capacity of the derivatising reagent can be exceeded. To address
this limitation, filters are extracted on site using a solution of the derivatising reagent.
A known volume of air is passed either through the MP solution in the glass impinger with an MP-treated
filter downstream (for aerosols) or directly through an MP-impregnated filter (for vapours). Any organic
isocyanates collected react with the MP reagent to form stable, non-volatile urea derivatives. The resulting
sample extract is then concentrated and analysed using high-performance liquid chromatography (HPLC)
with ultraviolet and visible (UV) and electrochemical (EC) detection. Peaks attributable to isocyanate
derivatives are identified based on their combined UV and EC responses, supported by diode array detection
(DAD) spectral library matching, mass spectrometric confirmation where available, and comparison with
[9]
derivatised bulk isocyanate material, see 9.8.1.
Where reference standards of MP-derivatised isocyanates are available (e.g. HDI, MDI, and TDI isomers),
quantification is performed using UV detection. In cases where appropriate standards are not available,
such as for isocyanate oligomers, prepolymers or polymers, EC detection is used for quantification, with
calibration based on the corresponding monomer standard. The overall airborne isocyanate concentration
is obtained by summing all peaks attributed to isocyanate.
5 Reagents
5.1 MP reagent [1-(2-methoxyphenyl)piperazine]. This reagent is commercially available with a purity
of >98 % by mass.
5.2 Toluene, of a purity suitable for HPLC.
NOTE Toluene (5.2) is commonly used as the reagent solvent, it must be free from compounds co-eluting with the
substance(s) of interest. Before use for the preparation of MP-impregnated filter (8.3.2) or for preparation of monomer
standards (7.2.1), it is advisable to dry the solvent with anhydrous calcium chloride or magnesium sulfate.
5.3 Acetonitrile, of a purity suitable for HPLC.
5.4 Methanol, of a purity suitable for HPLC.
5.5 Hexane, of a purity suitable for HPLC.
5.6 Dichloromethane, of a purity suitable for HPLC.
5.7 Water, of a purity suitable for HPLC, conforming with ISO 3696 Grade 1.
5.8 Anhydrous sodium acetate, of recognized analytical grade.
5.9 Acetic anhydride, of recognized analytical grade.
5.10 Glacial acetic acid, of recognized analytical grade.
6 Apparatus
Before sampling and analysis, clean (9.2) all glassware, including impingers (6.4). Usual laboratory
apparatus, and in particular the following, shall be used.
6.1 Sampler. The choice of sampler used depends on the form in which the isocyanate is present. For
vapour phase isocyanates, sampling can be carried out using an MP-impregnated filter (8.3.2) only. For
mixtures of airborne particles and vapour, the use of an impinger (6.4) backed by an MP-impregnated filter
is recommended.
6.2 Filter. Filters of diameter 25 mm are suitable for use in the selected sampler. The chosen filter type
should be suitable for collection of stable samples of isocyanate and have a capture efficiency of not less than
0,95, see 9.10 and Annex A. A glass fibre filter impregnated with 1,2-MP (5.1) reagent (8.3.2) is suitable, e.g.
1)
Whatman GF/A or equivalent.
[16]
6.3 Filter holder. Details of suitable sampling heads are given in MDHS14/4. A 25 mm Institute of
1)
Occupational Medicine (IOM) head fitted with a stainless-steel cassette is recommended for filter samples.
For aerosol sampling using the impinger (6.4) and filter (6.2) combination, it has been found to be more
1)
convenient to use the 25 mm Swinnex filter holder.
[10,11]
6.4 Midget impinger. Several designs of bubblers and impingers are available. A midget impinger
consists of a graduated receiver and a tapered inlet tube.
NOTE “Non-spill” impingers are commercially available.
6.5 Sampling pump, which shall fulfil the requirements of ISO 13137 or equivalent. Specific safety
regulations can apply.
6.6 Tubing, plastic, rubber or other suitable material, approximately 900 mm long, of appropriate diameter
to ensure a leak-proof fit to both pump (6.5) and sample tube or tube holder, if used. Fluoroelastomer or
similar tubing has been found to have fewer problems due to extraction of contaminants associated with
it. It is not recommended to use any tubing upstream of the first collection element [filter (6.2) or impinger
(6.4)] as sample losses can occur.
6.7 Flowmeter, portable, capable of measuring the appropriate flow rate to within ±1 %, and calibrated
[12]
against a primary standard. Flowmeters incorporated in sampling pumps (6.5) are not suitable for
accurate measurement of the flow rate. However, they can be useful for monitoring the performance of
samplers, provided they have adequate sensitivity.
6.8 Filtration equipment. A solvent resistant filter unit of < 0,5 µm pore size for filtration of LC solvents.
Syringeless filters or < 0,5 µm syringe filters for filtration of the desorbed samples prior to LC analysis.
6.9 Ancillary equipment.
6.9.1 Belts or harnesses, to which the sampling pump (6.5) can be conveniently fixed, unless the pump is
sufficiently small to fit into a worker’s pocket.
6.9.2 Flat-tipped tweezers for handling the filters.
6.9.3 Protective holder for impinger (6.4).
6.9.4 Charcoal trap to protect the sampling pump (6.5) from toluene vapour (if plastic pumps are being
used).
6.10 Liquid chromatograph. An HPLC (6.10) linked to UV and EC detectors is required. The EC detector
should be used in the oxidation mode. A DAD is also advisable for confirmation of identification. Temperature
fluctuations must be avoided to obtain the sensitivity required in this method. This can be achieved by fitting
the HPLC column and EC detector with a thermostat. EC performance can be improved by recirculating the
mobile phase in a closed loop and by use of a guard cell (set to approximately 50 mV above analytical cell
potential) before the injector. A pulse dampener will also decrease the LC system noise (pulse ripple) and so
increase signal to noise ratio.
1) GF/A, IOM and Swinnex are examples of suitable products available commercially. This information is given for
the convenience of users of this document and does not constitute an endorsement by ISO of this product. Equivalent
products may be used if they can be shown to lead to the same results.

6.11 HPLC autosampler. These are commercially available.
7 Reagent and calibration solutions
7.1 Reagent solutions
7.1.1 Absorbing solution
Accurately weigh approximately 50 mg of MP (5.1) and transfer to a dry 100 ml volumetric flask. Dissolve
and make up to the mark with reagent solvent (5.2) and mix thoroughly. Dilute 10 ml of this stock solution to
100 ml with reagent solvent in a second volumetric flask to give a 260 µM absorbing solution.
7.1.2 Preparation of solution for impregnating filters (solution A)
Accurately weigh out approximately 0,25 g of MP (5.1) and transfer to a 25 ml volumetric flask. Make up to
the mark with anhydrous reagent solvent (5.2) and shake to mix.
7.1.3 Stability of reagent solutions
Prepare fresh solutions weekly.
7.2 Calibration standards
7.2.1 Preparation of monomer derivatives
Add 0,1 g of the appropriate isocyanate (approximately 1 mmol for the common diisocyanates such as HDI,
TDI and MDI) to 0,6 g (approximately 3 mmol) of MP (5.1) dissolved in dry toluene (5.2) (10 ml) and leave
2)
to stand for 1 h. A white crystalline urea is precipitated. Collect this on a filter paper (e.g. Whatman No 1 )
and wash several times with dry toluene to remove excess reagent. Recrystallise the urea derivatives from
toluene, by warming to approximately 60 °C and slowly adding methanol (5.4) to dissolve the urea. Allow
to cool and then filter the resulting crystals, washing with cold, dry toluene. Dry the solid in air. The urea
derivatives of the monoisocyanates and most diisocyanates (3.2) are only slightly soluble in toluene but
readily soluble in acetonitrile (5.3) or methanol.
7.2.2 Alternative procedure for the less soluble isocyanate derivatives
MDI and H12MDI are rather insoluble in toluene and the alternative method of preparation given below can be
more suitable for these compounds. Slowly add a solution of the appropriate isocyanate (0,25 g, approximately
2 mmol NCO for MDI and H12MDI) in dichloromethane (5.6) (25 ml) to a solution of 1-(2-methoxyphenyl)
piperazine (1 g, approximately 5 mmol) in dichloromethane (50 ml). A white suspension will form. Add this
dropwise to a beaker of hexane (5.5) (500 ml) while stirring. Filter the resultant precipitate and redissolve
it in a minimum volume of dichloromethane. Add hexane to reprecipitate the solid, filter this and wash with
hexane. Dry the urea derivative in air.
NOTE This second method can also be used for isocyanate oligomers, polymers and prepolymers.
7.2.3 Preparation of standard solutions of recrystallised isocyanate monomer derivatives
Weigh out a known mass of the urea derivative, place in a 100 ml volumetric flask and make up to the
mark with acetonitrile (5.3) or methanol (5.4). Take aliquots of this solution and dilute volumetrically in
acetonitrile or HPLC mobile phase to create a series of standard solutions over the NCO concentration range
0,01 µg/ml to 1,0 µg/ml.
2) Whatman No 1 is an example of a suitable product available commercially. This information is given for the convenience
of users of this document and does not constitute an endorsement by ISO of this product. Equivalent products may be
used if they can be shown to lead to the same results.

Prepare further standard solutions if the concentration range of the samples exceeds that of the standards.
The concentration of isocyanate in the standard, ρ , in micrograms per millilitre, is given by Formula (1):
NCO
 Mn
UNCO
  (1)
NCO
M
U
where
ρ is the concentration, in micrograms per millilitre, of the urea derivative in the standard;
U
M is the relative molecular mass of NCO;
NCO
n is the number of isocyanate groups per molecule;
M is the relative molecular mass of the urea derivative.
U
7.2.4 Stability of isocyanate ureas and their solutions
Stock solutions of isocyanate monomer derivatives have been found to be stable for approximately 6 months
[12]
if kept in a freezer. A mixture of 2,4-TDI and 2,6-TDI on filters (6.2) and in toluene solution has been found
[13].
to be stable for up to 90 days (73 %, filter, and 81 %, toluene solution, recoveries, respectively) MDI on
filters has been found to be stable for at least 6 months [HSE Workplace Analysis Scheme for Proficiency
[1] ® 3)
(WASP) data]. An isocyanate prepolymer [Desmodur N 3390] ] spiked onto MP (5.1) filters was found to
[14]
be stable for 27 days (average recovery 91 ± 11 %, spiked at three levels, 0,1, 1 and 2 µg/filter) .
7.3 HPLC mobile phase
7.3.1 General
The exact composition of the mobile phase used depends on the isocyanate formulation being determined.
The more acetonitrile in the mobile phase, the faster the peaks will elute. A low elution strength mobile phase,
or “slow” mobile phase, can be used for monomeric diisocyanates and monoisocyanate MP derivatives. For
the polymeric isocyanate MP derivatives, a mobile phase with increased elution strength, or “fast” mobile
phase, is more suitable. Care shall be taken to elute all the polymeric MP derivatives and not to lose any
monomeric species under the acetylated MP reagent peak at the start of the chromatogram.
7.3.2 Preparation of “slow” mobile phase
A “slow” mobile phase, sui
...