ISO 17734-1:2006

INTERNATIONAL ISO
STANDARD 17734-1
First edition
2006-03-01
Determination of organonitrogen
compounds in air using liquid
chromatography and mass
spectrometry —
Part 1:
Isocyanates using dibutylamine
derivatives
Détermination des composés organiques azotés dans l'air par
chromatographie liquide et spectrométrie de masse —
Partie 1: Isocyanates par les dérivés de la dibutylamine

Reference number
©
ISO 2006
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ii © ISO 2006 – All rights reserved

Contents Page
Foreword. iv
Introduction . v
1 Scope . 1
2 Normative references . 1
3 Principle. 1
4 Reagents and materials . 3
5 Preparation of standard solutions . 3
5.1 Reference compounds . 3
5.2 Di-n-butylamine (DBA) derivatives of isocyanates . 4
5.3 DBA derivatives of bulk isocyanates. 5
5.4 DBA derivatives of isocyanates in thermal decomposition products of polyurethane
(PUR) or urea-based resins . 6
5.5 Stability . 6
6 Apparatus . 6
7 Air sampling . 9
7.1 Pre-sampling laboratory preparation. 9
7.2 Pre-sampling field preparations. 9
7.3 Collection of air samples . 9
7.4 Blanks . 10
7.5 Raw material. 11
7.6 Shipment of samples. 11
8 Laboratory sample preparation. 11
8.1 Sample sequence. 11
8.2 Work-up procedure. 11
9 Instrumental settings. 12
9.1 HPLC program (LC-MS). 12
9.2 HPLC program (LC-chemiluminescent nitrogen detector) (LC-CLND) . 12
9.3 Mass spectrometer . 12
10 Data handling . 12
10.1 Identification. 12
10.2 Calibration curves. 13
10.3 Quantification. 13
11 Interferences . 13
12 Determination of performance characteristics. 13
12.1 Introduction . 13
12.2 Relevant uncertainty contributions and criteria. 14
12.3 Assessment of performance characteristics, following the detailed approach in
Reference [18] . 14
Annex A (informative) Performance characteristics. 22
Annex B (informative) Examples . 24
Bibliography . 28

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.
International Standards are drafted in accordance with the rules given in the ISO/IEC Directives, Part 2.
The main task of technical committees is to prepare International Standards. Draft International Standards
adopted by the technical committees are circulated to the member bodies for voting. Publication as an
International Standard requires approval by at least 75 % of the member bodies casting a vote.
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.
ISO 17734-1 was prepared by Technical Committee ISO/TC 146, Air Quality, Subcommittee SC 2, Workplace
Atmospheres.
ISO 17734 consists of the following parts, under the general title Determination of organonitrogen compounds
in air using liquid chromatography and mass spectrometry:
⎯ Part 1: Isocyanates using dibutylamine derivatives
⎯ Part 2: Amines and aminoisocyanates using dibutylamine and ethyl chloroformate derivatives
iv © ISO 2006 – All rights reserved

Introduction
Isocyanates have been used in industry for about 50 years. They are commercially important chemicals
mainly used for the production of polyurethane (PUR). In spite of controls to limit exposures, there are adverse
health effects such as asthma, contact dermatitis and hypersensitivity pneumonitis as a consequence of
exposure to isocyanates in some industrial sectors.
The analytical method for the determination of isocyanates in workplace air must be sensitive due to the high
irritation and sensitization properties of isocyanates. Extremely low occupational exposure limits (OELs) exist
in many countries, and concentrations well below the OEL (< 1/100) often must be determined. Isocyanates
are very reactive and therefore cannot be analysed directly. Derivatization during sampling is required in order
to prevent interfering reactions. Hundreds of different isocyanates are used in industry, and many more are
formed during thermal degradation of PUR. Therefore the analytical method must be highly selective.
The determination of isocyanates in the work environment using di-n-butylamine (DBA) as a reagent and
liquid chromatography-mass spectrometric detection (LC-MS) has been demonstrated to be a robust method.
The development of the method was initiated when difficulties using the “older” methods during sampling of
[1], [2], [3]
isocyanates in complex atmospheres were encountered (e.g. thermal decomposition of PUR) . The
reaction rate between DBA and isocyanates was found to be fast, and high concentrations can be used to
[4], [5]
secure instantaneous reactions and eliminate problems with interfering compounds . Using impinger
flasks containing a reagent solution and a filter in series efficiently collects and derivatizes isocyanates in both
[6]
the gas and the particle phase . LC-MS/MS of the isocyanate-DBA derivatives enables highly selective and
–6 [7]
precise determinations down to levels below 10 of the OEL .
Solvent-free sampling can also be performed by using a tube coated with a DBA-impregnated glass fibre filter
followed by an impregnated filter. An impregnation solution containing DBA together with an acid is used, and
[8]
the formed ion pair reduces volatility. DBA remains on the filter even after 8 h of sampling .
Monomeric isocyanates that are formed during thermal decomposition of polymers [typically PUR and
phenol/formaldehyde/urea (PFU)-resins], such as isocyanic acid and methyl isocyanate, can also be
[6], [7], [8], [9], [10]
determined . Volatile isocyanate DBA derivatives can be determined using gas
[9]
chromatography (GC)-MS . Using the DBA-method and derivatization with ethyl chloroformate makes
simultaneous determinations of amine, aminoisocyanates and isocyanates possible, as described in the
companion method ISO 17734-2.
For quantification, reference compounds are necessary but are only available for a few monomeric
isocyanates. Most of the isocyanates that are used in industry for the production of PUR can only be obtained
in technical grade mixtures. Many isocyanates that are formed during thermal degradation are not available
and are not easily synthesized. In this method, a nitrogen sensitive detector has been used for quantifying
isocyanates in reference solutions. This technique has been demonstrated to be a useful tool, together with
[10], [11], [12]
MS characterization, in greatly facilitating the production of reference solutions .
For quantifying isocyanates in complex mixtures, MS detection is necessary and provides a unique possibility
of identifying unknown compounds. This method has enabled assessment of new areas for which exposure to
isocyanates previously was not known and has identified new kinds of isocyanates in the work
[6], [7], [8], [9], [10], [11], [12]
environment .
INTERNATIONAL STANDARD ISO 17734-1:2006(E)

Determination of organonitrogen compounds in air using liquid
chromatography and mass spectrometry —
Part 1:
Isocyanates using dibutylamine derivatives
1 Scope
This part of ISO 17734 gives general guidance for the sampling and analysis of airborne isocyanates in
workplace air. When amines and aminoisocyanates are suspected to be emitted (e.g. from thermal
degradation of PUR), it is recommended that in addition to isocyanates the amines and aminoisocyanates in
air are determined, using DBA and ethyl chloroformate as reagents (ISO 17734-2).
The method is suitable for the determination of a wide range of different isocyanates in both the gas and
particle phases. Typical monofunctional isocyanates that can be determined are isocyanic acid (ICA), methyl
isocyanate (MIC), ethyl isocyanate (EIC), propyl isocyanate (PIC), butyl isocyanate (BIC), and phenyl
isocyanate (PhI). Typical monomeric diisocyanates include 1,6-hexamethylene- (HDI), 2,4- and 2,6-toluene-
(TDI), 4,4’-diphenylmethane- (MDI), 1,5-naphthyl- (NDI), isophorone- (IPDI), and 4,4’-dicyclohexylmethane
diisocyanate (HMDI). Multifunctional isocyanates that can be determined are typically oligomers in polymeric
MDI, biuret-, isocyanurate-, and allophanate-adducts and prepolymeric forms of isocyanates.
The instrumental detection limit for aliphatic isocyanates is about 50 fmol and for aromatic isocyanates, it is

–3 –3
2 fmol. For a 15-l air sample, this corresponds to 0,6 ng⋅m for HDI and 0,02 ng⋅m for TDI.
–3 –3
The useful range, for a 5-l air sample, of the method is approximately 0,001 µg⋅m to 200 mg⋅m for TDI.
2 Normative references
The following referenced documents are indispensable for the application 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 16200-1:2001, Workplace air quality — Sampling and analysis of volatile organic compounds by solvent
desorption/gas chromatography — Part 1: Pumped sampling method
ISO 5725-2:1994, 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 (including
Technical Corrigendum 1:2002)
3 Principle
Samples are collected by drawing a known volume of air through a midget impinger flask followed by a filter.
–1
The impinger contains 10 ml of 0,01 mol l of DBA in toluene and the filter is a glass fibre filter with no binder.
Solvent-free sampling can also be performed by drawing air through a tube coated with a DBA-impregnated
glass fibre filter followed by an impregnated filter. An impregnation solution containing DBA together with
acetic acid is used, the ion pair so formed reducing the volatility and enabling long-time sampling.
After sampling, deuterium-labelled DBA-isocyanate derivatives (used as internal standard) are added to the
sample solutions. The excess reagent and solvent are evaporated, and the samples are dissolved in
acetonitrile. The samples are analysed using reversed-phase LC and electrospray (ESP)-MS detection,
monitoring positive ions. Quantification is made by monitoring selected ions. See Figure 1.
Quantification and qualitative determinations can be performed using different LC-MS or LC-MS/MS
techniques. LC-CLND (chemiluminescent nitrogen detection) or for aromatic isocyanates LC-UV (ultraviolet
detection) can be used for the determination of higher concentrations of isocyanates.
Reference materials can be characterized using LC-MS/CLND. For characterization of volatile compounds,
GC-thermionic specific detector (TSD) can also be used.

Figure 1 — Principle of the described method
2 © ISO 2006 – All rights reserved

4 Reagents and materials
4.1 DBA reagent.
Analytical grade di-n-butylamine is commercially available.
4.2 Solvents.
The reagent solvent, typically toluene, and other solvents, acetonitrile, isooctane and methanol, should be of
liquid chromatographic quality.
4.3 Formic acid, concentrated formic acid, analytical grade.
4.4 Acetic acid, concentrated acetic acid, analytical grade.
4.5 Reagent solution.
In a 1-l volumetric flask, dilute 1,69 ml of DBA in toluene, and make up to the mark. The solution is stable and
no special care during storage is necessary.
4.6 Reagent solution for solvent-free sampler.
–1
4.6.1 Solution 1: 0,74 mol l DBA.
Mix 80 ml methanol and 12,5 ml DBA in a 100 ml volumetric flask. Then while stirring, slowly add 4,16 ml of
acetic acid to the flask. Finally, add methanol to the flask, and make up to the mark.
–1
4.6.2 Solution 2: 1,5 mol l DBA.
Mix 60 ml methanol and 25 ml DBA in a 100 ml volumetric flask. Then while stirring, slowly add 8,32 ml of
acetic acid to the flask. Finally, add methanol to the flask, and make up to the mark.
4.7 HPLC mobile phases.
4.7.1 LC-MS.
The weak mobile phase (mobile phase A) consists of water/acetonitrile (95/5 volume fraction) and 0,05 %
formic acid. The strong mobile phase (mobile phase B) consists of water/acetonitrile (5/95 volume fraction)
and 0,05 % formic acid. The mobile phases are degassed prior to use.
4.7.2 LC-CLND.
The weak mobile phase (mobile phase C) consists of water/methanol (95/5 volume fraction) and 0,05 %
formic acid. The strong mobile phase (mobile phase D) consists of water/methanol (5/95 volume fraction) and
0,05 % formic acid. The mobile phases are degassed prior to use.
5 Preparation of standard solutions
5.1 Reference compounds
Reference compounds are necessary for LC-MS determination of isocyanate derivatives. For the
commercially available isocyanates, the DBA derivatives are easily prepared by direct derivatization with DBA.
DBA derivatives for the isocyanates not commercially available can be made from the bulk material or from
the thermal decomposition of PUR or urea-based resins used at the work place. Alternatively, standard
solutions can be purchased.
5.2 Di-n-butylamine (DBA) derivatives of isocyanates
5.2.1 Preparation of isocyanate-DBA derivatives of commercially available isocyanates
Many frequently used isocyanates are commercially available from companies supplying laboratory chemicals
such as HDI, 2,4-and 2,6-TDI, 4,4’-MDI, 4,4’-HMDI, 1,5-NDI, IPDI, PHI, MIC, EIC, PIC and BIC. The purity of
the isocyanates varies, and some contain isomers.
Calibration standards are made by spiking accurately weighed amounts or volumes (ca 0,1 mmol) of

–1
isocyanates in 100 ml of isooctane. A 1-ml volume is added to 100 ml of toluene containing 0,01 mol⋅l of
–1
DBA (ca 0,01 µmol⋅ml of the DBA derivative).
Synthesis of derivatives:
⎯ Dilute 6 mmol of isocyanate in 2 ml of isooctane, and dissolve 60 mmol of DBA in 20 ml of isooctane.
⎯ Add the isocyanate solution to the DBA solution dropwise under continuous stirring.
⎯ Evaporate the reaction mixture to dryness in a rotating evaporator, and dry the residue under vacuum to
remove excess DBA.
It is also possible to prepare the isocyanate-DBA derivatives by collecting thermal degradation products of
corresponding carbamate esters in an impinger flask containing DBA solution (as in 5.2.3.3).
5.2.2 Preparation of ICA and MIC-DBA
When urea is thermally degraded, isocyanic acid (ICA) is formed.
Heat an amount of urea (20 mg) to about 300 °C in a glass tube. Collect the degradation products in an
–1
impinger flask containing DBA in toluene (0,5 mol⋅l ). Wash the toluene solution containing the ICA-DBA
derivatives with water, whereupon the organic phase is evaporated in a vacuum centrifuge and the residue is
dissolved in methanol. Characterize the solution as described in 5.2.4.
The same procedure can be applied for preparation of MIC-DBA derivatives, by collecting thermal degradation
products of 1,3-dimethyl urea.
5.2.3 Preparation of deuterium-labelled isocyanate-DBA derivatives
5.2.3.1 Internal standards
For accurate LC-MS quantifications, it is important to use proper internal standards, not only to compensate
for variations during the work-up procedure, but also to compensate for fluctuation in the MS instrument
response. Ideally, each analyte should have its own deuterium-labelled analogue. For isocyanate-DBA
determinations, it is possible to use DBA derivatives of deuterium-labelled isocyanates or d - and d -DBA
9 18
derivatives of the isocyanates as internal standards.
The quality of the quantification is influenced by the number of deuterium substitutions in the internal standard
(less deuterium in the molecule resulting in higher precision). Having the deuterium on the isocyanate, and not
on the DBA, has advantages when performing structural identification using MS and MS/MS. It is then
possible to distinguish between labelled and non-labelled fragments that originate from the isocyanate itself.
Therefore, the ideal internal standards are the DBA derivatives of the deuterium-labelled isocyanates.
However, they are labour intensive to prepare, and they are only available for a few isocyanates.
The deuterium-labelled d - and d -DBA derivatives are easy to prepare, and any technical isocyanate or
9 18
thermal degradation product can be derivatized and used as internal standard.
4 © ISO 2006 – All rights reserved

5.2.3.2 DBA derivatives of deuterium-labelled isocyanates
Dissolve a 10 mmol aliquot of the deuterium-labelled corresponding amine in 20 ml of toluene. Thereafter, add
–1
150 µl pyridine and 40 ml of 5 mol⋅l NaOH. Then add 1,5 ml of ethyl chloroformate dropwise under
continuous stirring. After 10 min, the toluene phase is separated, and the solvent is evaporated.
Place the residue containing the formed amine carbamate ester (10 µl) in a glass tube. Heat the tube to about
–1
300 °C. By connecting the tube to an impinger flask, containing 0,5 mol⋅l DBA in toluene, the formed
deuterium-labelled isocyanate is collected as a DBA derivative. Evaporate the solvent, and dissolve the
residue in methanol to an appropriate concentration. Characterize the solution as described in 5.2.4.
5.2.3.3 d -DBA and d -DBA derivatives of the isocyanates.
9 18
Prepare the deuterium-labelled d - and d -DBA derivatives by dissolving accurately weighed amounts of
9 18
–1
the isocyanates in 10 ml of 0,1 mol⋅l d -DBA or d -DBA in toluene.
9 18
Prepare the deuterium-labelled derivatives of ICA and MIC by placing an amount (20 mg) of urea (for ICA)
and 1,3-dimethyl urea (for MIC) in a glass tube. Heat the tube to about 300 °C and collect the formed ICA and

–1
MIC in impinger flasks containing 0,1 mol⋅l d -DBA or d -DBA in toluene. Evaporate the solutions
9 18
containing the isocyanate d -DBA or d -DBA derivatives to dryness, and dissolve the residues in methanol.
9 18
Characaterize the solution as described in 5.2.4.
5.2.4 Characterization
The solutions are diluted in methanol to appropriate concentrations and characterized on the LC-MS and
quantified on the LC-CLND. This technique is nitrogen specific and any nitrogen-containing compound can be
[13], [14], [15]
used as external standard, e.g. caffeine. The technique is used in several applications .
Quantification of volatile isocyanate-DBA derivatives can also be made by using GC-TSD.
5.3 DBA derivatives of bulk isocyanates
5.3.1 Preparation
Technical isocyanates used in industry are typically available in mixtures such as oligomers in polymeric MDI,
biuret-, isocyanurate-, alophanate-adducts and prepolymeric forms of isocyanates. These isocyanates are
typically multifunctional.
If product data sheets are available and correct, standard solutions for the technical grade isocyanates can be
prepared in the same way as described in 5.2.1 by adding a known amount of bulk isocyanate to a toluene
solution of DBA. If data regarding the composition and concentrations of different isocyanates are of poor
quality or missing, the bulk material must to be characterized.
The procedure for technical grade isocyanate is as follows.
–1
⎯ Add an aliquot of 10 mg of the isocyanate product to a 10 ml vial containing 0,5 mol DBA⋅l .
⎯ Sonicate the solution and evaporate it to dryness and then dissolve it in methanol.
⎯ Further dilute the solution with methanol to appropriate concentrations.
⎯ Characterize the solution as described in 5.3.2.
5.3.2 Characterization
If the isocyanates that are present in the bulk are known or reference compounds are available, calibration
standards can be prepared as in 5.2.1.
If the isocyanates that are present in the bulk are unknown, qualitative data are obtained with full scan
chromatograms for DBA derivatized bulk material. Obtained structural data together with the LC-CLND data
make it possible to calculate the concentrations of the different components in the solution. The characterized
bulk sample solution is used as a calibration standard for LC-MS.
When prepolymeric forms or complex isocyanates are to be determined, it may be difficult to quantify each
individual isocyanate using LC-MS. However, one or more components can be used as index compounds.
[16]
The total isocyanate group (NCO) concentration of the bulk is obtained by titration with DBA and standard
solutions can be prepared (dilution). The concentration of isocyanates in the air sample is estimated by
comparison of peak areas. This may be performed with the assumption that the composition of the bulk
material reflects the composition of the airborne isocyanates. The obtained result gives the concentration of
total isocyanate content in the air. However, detection limits are increased by the factor of the ratio of total
isocyanate concentration and the assumed concentration of the index isocyanate. Still, in most cases, levels
below 1/10 of the threshold limit value (TLV) are possible to determine.
5.4 DBA derivatives of isocyanates in thermal decomposition products of polyurethane
(PUR) or urea-based resins
5.4.1 Preparation
During the thermal decomposition of e.g. PUR or urea-based resins, isocyanates are formed that are not
commercially available. PUR or urea-based material can be thermally decomposed at appropriate
temperatures. Emitted degradation products are collected in impinger flasks (filters in series) containing
–1
0,5 mol DBA⋅l . The solutions are evaporated to dryness and the residues are dissolved in methanol.
5.4.2 Characterization
Qualitative data are obtained with LC-MS. Obtained structural data together with the LC-CLND data make it
possible to calculate the concentrations of different components in the solution. The characterized diluted
sample solution is used as a calibration standard for LC-MS.
5.5 Stability
Solutions of isocyanate-DBA derivatives (MDI, 2,4- and 2,6-TDI, HDI, IPDI, PhI, BIC, PIC, EIC, MIC and ICA)
have been found stable in toluene, acetonitrile and methanol for six months when stored at 8 °C. NDI-DBA
has limited stability and must be freshly prepared and quantified before using as a calibration standard.
6 Apparatus
6.1 Sampler.
Sample the air with an impinger flask followed by a filter.
6.1.1 Filter.
Use a 13-mm glass fibre filter (binder free) with a pore size of 0,3 µm.
6.1.2 Filter holder.
Use a 13-mm polypropylene filter holder with luer-lock connections.
6.1.3 Midget impingers.
A midget impinger consists of a tapered inlet tube. Match the two parts so that the distance between the inlet
and the receiver bottom is 1 mm to 2 mm. A luer-lock fitting is attached to the outlet of the impinger.
6 © ISO 2006 – All rights reserved

6.1.4 Solvent-free sampler.
Cut out two kinds of glass fibre filters from a filter sheet of type MG 160 with a pore size of 0,3 µm:
⎯ one rectangular filter, 2,5 cm × 6 cm; and
⎯ one round filter with a diameter of 13 mm.
Impregnate the filters with by adding
–1
⎯ 1 ml of solution 2 (1,5 mol⋅l DBA) to the rectangular filter, and
–1
⎯ 0,1 ml of solution 1 (0,74 mol⋅l DBA) to the round filter.
Allow the solvent to evaporate from the filters at room temperature for 1 h.
Place the rectangular filter inside a polypropylene tube (L = 7 cm, ID = 0,8 cm), so that it covers the inner walls
of the tube, and the round filter in a 13-mm polypropylene filter holder. Connect the filter holder in series after
the tube (Figure 2). Plug both ends of the sampler with polypropylene plugs and store the sampler in
refrigerator prior to air sampling.
Dimensions in millimetres
a –1
Quantity = 0,21 l min .
NOTE Glass-fibre filter was impregnated with DBA and acetic acid 0,3 µm pore size.
Figure 2 — Solvent-free sampler
6.1.5 Sampling pump.
–1 –1
The sampling pump needs to have a calibrated flow of 1 l⋅min for impinger-filter sampling and 0,2 l⋅min for
solvent free sampling.
6.1.6 Tubing.
Use rubber tubing of suitable length and of appropriate diameter to ensure a leak-proof fit to both the pump
and the sampler outlet.
6.1.7 Vapour trap.
Use a vapour trap (with an internal diameter of 17 mm and a length of 140 mm) filled with charcoal (with a
medium particle size < 3 mm) between the impinger-filter and the sampling pump.
6.2 Flow meter.
Use a portable flow meter capable of measuring the appropriate flow rate with an acceptable accuracy.
6.3 Liquid chromatographic system.
In this method, a micro-LC system is used, in order to improve the sensitivity, to minimize the maintenance on
the MS and to minimize the consumption of the mobile phase. The micro-LC system is described in the
following paragraphs. If desired, this system can be replaced by a conventional LC-system.
6.3.1 Autosampler.
6.3.1.1 LC-MS.
On-column focusing is performed by partially filled loops (typically 10 µl total volume) of 2 µl loop injections
between 4+4 µl of 50/20/30 water/methanol/acetonitrile. Any commercially available autosampler capable of
making partially filled loop injections and making sample injections of acceptable accuracy and precision can
be used.
6.3.1.2 LC-CLND.
On-column focusing is performed by partially filled loops (typically 10 µl total volume) of 2 µl loop injections
between 4+4 µl of 50/50 methanol/water. Any commercially available autosampler capable of making partially
filled loop injections and making sample injections of acceptable accuracy and precision can be used.
6.3.2 Pumping system (LC-MS and LC-CLND).
–1
An HPLC-pump capable of gradient elution with a flow rate of 100 µl min is required.
6.3.3 Analytical column (LC-MS and LC-CLND).
An HPLC-column capable of separating the different isocyanate derivatives is required.
® 1)
EXAMPLE An example of a suitable column is a PepMap C (50 × 1,0 mm with 3 µm particles).
6.3.4 Tubing.
Use short (< 40 cm) tubing with a small internal diameter (typically ID < 0,1 mm).
6.3.5 Detectors.
6.3.5.1 LC-MS.
Any modern MS equipped with a robust and stable electrospray interface will have the necessary performance.
MS detection is performed with atmospheric pressure ionization, monitoring positive ions. For quantification,
selected ions are monitored. Full spectra are obtained using continuum scans (typically 50 amu to 1 500 amu)
for identification of unknown isocyanates. If desired, a UV-detector can be used in series, prior to the MS. The
UV-detector needs to be equipped with a micro flow cell (typically 300 nl) to minimize peak band broadening.
6.3.5.2 LC-CLND.
Use a detector which is specific for bound nitrogen.
®
1) PepMap is an example of a suitable product available commercially. This information is given for the convenience of
users of this part of ISO 17734 and does not constitute an endorsement by ISO of this product.
8 © ISO 2006 – All rights reserved

7 Air sampling
7.1 Pre-sampling laboratory preparation
7.1.1 Cleaning of sampling equipment
Impingers should be taken apart and soaked in alkaline cleaning solution for a minimum of 2 h. The upper part
must be rinsed with an alkaline cleaning solution, pure water and finally deionized water. If the nozzle is
clogged, place it in an ultrasonic bath, and then continue with the cleaning procedure. The lower part should
be cleaned in a laboratory dishwasher. Both parts should be dried in an oven.
The filter cassettes and the gaskets should be immersed in ethanol in a glass beaker, sonicated for at least
15 min, rinsed with deionized water and dried in an oven.
7.1.2 Preparation of reagent solution and extraction solution tubes
–1
Prepare test tubes containing 10 ml of 0,01 mol⋅l DBA as the reagent solution for the impingers. If the gas
phase and the particulate phase are to be collected separately, prepare test tubes containing 10 ml of
–1
0,01 mol l DBA as extraction solution tubes for the filters.
7.2 Pre-sampling field preparations
Assemble the sampling system with the filter cassette containing the glass fibre filter coupled to the outlet of
the impinger. Transfer the reagent solution to the impinger.
Calibrate the pumps with the impinger-filter sampling system in line, using a portable flow meter. Fill the
impinger with the appropriate amount of reagent solution during calibration. The sampling rate should be
–1
1 l⋅min .
7.3 Collection of air samples
7.3.1 Sampling
In order to relate measurement results to occupational exposure limit values, take samples in the worker's
breathing zone. In order to illustrate risks of being exposed, take stationary samples at every place at the
worksite where isocyanates can be emitted into the air. It is also important to include operations that are not
frequently performed, for example repair and maintenance. Differences in materials and batch-to-batch
variations are factors that also should be taken into account when sampling. Collect a sufficient number of
samples in order to make a representative exposure assessment.
7.3.2 Impinger-filter sampling
Position the sampling system, either attached to the worker with the inlet in the breathing zone for personal
samples, or stationary for area samples. Connect the pump to the sampling system, and place a charcoal
vapour trap in line between the pump and the sampling system in order to protect the pump from the solvent
vapour. Make sure that the equipment does not disturb the work operation, and that the impinger can be held
in a vertical position during the whole sampling period.
When ready to begin sampling, switch on the pump. Record the time of sampling. At the end of the sampling
period, measure the flow and turn off the pump. Transfer the impinger solution to a test tube, and immerse the
glass fibre filter into either the sampling solution or an extraction solution tube using tweezers. If the filter is
transferred to an extraction solution, it is possible to determine the amount of isocyanates in the particulate
phase that passes through the impinger (i.e. particles approx. 0,01 µm to –1,5 µm), separately from the gas
phase and large particles (>1,5 µm) sampled in the impinger. For an illustration of the sampling procedure,
see Figure 2. Calculate the volume drawn through the sampler from the sampling time and the average
sampling flow. The total sampling time is limited (about 30 min), unless the reagent solution is refilled during
sampling.
a
The impinger solution is transferred to the impinger flask.
b
The airflow is measured and the sampling pump is calibrated to 1 l/min.
c
Air sampling.
d
The airflow is measured.
e
The impinger solution is transferred to a test tube. The filter is either transferred to the impinger solution tube or to an
extraction solution tube.
Figure 3 — Illustration of the sampling procedure
7.3.3 Solvent-free sampling
Take off the plugs in both ends just prior to the air sampling. Connect an air sampling pump to the filter-holder
outlet with a charcoal vapour trap between the sampler and the pump. Perform air sampling with an air flow of
–1
0,2 l min before and after sampling. After sampling, disconnect the sampler from the pump, and plug both
ends with polypropylene plugs. Keep the samplers cold during transport back to the laboratory.
7.4 Blanks
From every series of samples, there should be an appropriate number of field blanks collected. Field blanks
are samples that have been handled exactly like the other samples out in the field, except that no air has been
drawn through.
10 © ISO 2006 – All rights reserved

7.5 Raw material
From each work-site, it is desirable to collect samples of the raw material suspected of emitting isocyanates
during the work operation. If the material is a bulk isocyanate product, it could be useful for qualitative
identification of isocyanate species in the air samples. These products are also applicable for preparation of
reference solutions for quantification of unknown isocyanates (see 5.2 and 5.3).
Collecting and subsequent laboratory testing of materials that are known or are suspected of emitting
isocyanates is useful for assessing the exposure. The testing may consist of extraction, heating or other
processing of the material, as similar to the original work operation as possible.
7.6 Shipment of samples
The test tubes containing the DBA-toluene samples should be shipped in individual plastic cases and
preferably kept in an upright position. The sampling solution tubes should be placed well apart from any raw
material collected.
8 Laboratory sample preparation
8.1 Sample sequence
In each sample sequence (typically 50 samples), a number of samples consist of field blanks, two chemical
blanks, two internal standard blanks and an appropriate number of calibration standards. Internal standard
blanks are reagent solutions from the same batch as the reagent solution used for air sampling spiked with
internal standard in the work-up procedure. Chemical blanks are pure toluene with no addition of internal
standard in the work-up procedure.
8.2 Work-up procedure
8.2.1 General
–1
For preparation of calibration standards, aliquots of 10 ml toluene solutions, containing 0,01 mol l DBA, are
spiked with the isocyanate-DBA derivatives to concentrations appropriate for the calibration curve.
Upon receiving air samples from the field, add internal standards (deuterium-labelled isocyanate derivatives)
to the air samples, to the standard solutions, to the field blanks and to the internal standard blanks. Place the
samples in an ultrasonic bath for 15 min. If the solutions contain filters, place the samples in a centrifuge for
10 min (3 000 r/min). Remove the sample solutions from the filters with a pipette into new test tubes.
Evaporate the solvent from the samples and the standards. Dissolve the residues in 0,5 ml acetonitrile and
place them in an ultrasonic bath for 15 min.
8.2.2 Solvent-free sampling
Connect the samplers to a work-up station, where vacuum suction can be applied. Fill the samplers with 3 ml
–1
of 1 mmol l H SO (aq), wait approx. 2 min and then let the extraction solution be sucked down through the
2 4
sampler. When the samplers are dry, repeat this procedure once with 3 ml of methanol and twice with 3 ml of
toluene. Collect all the four-step extraction solutions in the same test tube.
Prepare calibration standards in test tubes containing the same extraction solutions as the extracted air
samples. Add internal standards to the air samples, to the standard solutions, to the field blanks and to the
internal standard blanks. Shake the extraction solutions for 10 min, centrifuge for 10 min, and transfer the
toluene phases to new test tubes. Remove the solvent and the excess reagent from the samples by
evaporation. Dissolve the residues in 0,5 ml acetonitrile and place them in an ultrasonic bath for 15 min.
9 Instrumental settings
9.1 HPLC program (LC-MS)
For simultaneous determination of the DBA derivatives of mono-isocyanates and diisocyanates, the following
mobile phase composition can be used:
–1
⎯ Flow rate: 100 µl min ;
⎯ 0 – 15 min: Linear gradient from 50 % mobile phase B to 90 % mobile phase B;
⎯ 15 – 20 min: Re-equilibrate at 50 % mobile phase B.
If a single or a few derivatives are to be determined, isocratic elution or gradient elution with appropriate
mobile phase composition can be performed.
If high molecular weight DBA derivatives (e.g. prepolymers, isocyanate adducts) are to be determined
together with DBA monomers, it is necessary to continue with the gradient up to 100 % B and maintain at
100 % B for isocratic elution.
9.2 HPLC program (LC-chemiluminescent nitrogen detector) (LC-CLND)
–1
⎯ Flow rate: 100 µl min ;
⎯ 0 – 15 min: Linear gradient from 40 % mobile phase D to 100 % mobile phase D;
⎯ 15 – 30 min: 100 % mobile phase D;
⎯ 30 – 35 min: Re-equilibrate at 40 % mobile phase D.
Depending on the properties of the analytes in the sample, stronger, weaker or isocratic elution can be used.
9.3 Mass spectrometer
Settings of the MS depend greatly on which type of instrument that is used. Optimization is normally
performed by the introduction of flow at 100 µl/min of mobile phase containing low and high mass aromatic
and aliphatic isocyanate derivatives. Optimal settings vary for the analytes and the ions to be monitored.
Practical settings are not the optimum for all of the compounds to be studied.
+
For quantification, selected ions are monitored, e.g. the molecular ion [MH] , but other typical ions can be
+ + + +
used: [(DBA)H] (m/z = 130), [(DBA)CO] (m/z = 156), [MH-129] and [MNa] (see B.4).
For LC-MS/MS quantifications, multiple reaction monitoring is performed by monitoring the daughter ion
+ + + +
[(DBA)H] , [(DBA)CO] or [MH-129] from the protonated molecular ion [MH] .
For identification of unknown isocyanates, full spectra are obtained using continuous scans (typically 50 amu
to 1 500 amu).
10 Data handling
10.1 Identification
For
...