ASTM D6561-20

Standard Test Method for Determination of Aerosol Monomeric and Oligomeric Hexamethylene Diisocyanate (HDl) in Air with (Methoxy-2–phenyl-1) Piperazine (MOPIP) in the Workplace

SIGNIFICANCE AND USE
5.1 HDI is mostly used in the preparation of paints. The use of isocyanates and their industrial needs have been in constant growth.  
5.2 Diisocyanates and polyisocyanates are irritants to skin, eyes, and mucous membranes. They are recognized to cause respiratory allergic sensitization, asthmatic bronchitis, and acute respiratory intoxication (3-6).  
5.3 The American Conference of Governmental Industrial Hygienists (ACGIH) has adopted a threshold limit value–time weighted average (TLV-TWA) of 0.005 ppm (V) or 0.034 mg/m3 for monomeric HDI (7). The Occupational Safety & Health Administration of the U.S. Department of Labor (OSHA) has not listed a permissible exposure limit (PEL) for HDI (8).  
5.4 In any case, there are not separate exposure standards for vapor and aerosol. Therefore, in comparing the results for isocyanate against a standard, results from the two fractions should be combined to give a single total value.  
5.5 Due to its low LOD and low required volume (15 L), this test method is well suited for monitoring of respiratory and other problems related to diisocyanates and polyisocyanates. Its short sampling times are compatible with the duration of many industrial processes, and its low detection limit with the concentrations often found in the working area.
SCOPE
1.1 This test method covers the determination of aerosol hexamethylene diisocyanate (HDI) in air samples collected from workplace and ambient atmospheres. The method described in this test method collects separate fractions. One fraction will be dominated by vapor, and the other fraction will be dominated by aerosol. The results obtained from the analysis of the separate fractions do not necessarily represent the true partition of the measured HDI physical phases, and should only be considered a representation of the general trend in the physical phase partition within samples. The analyses of the two fractions are different, and are provided in separate, linked, standards to avoid confusion. This test method is principally used to determine short term exposure (15 min) of HDI in workplace environments for personal monitoring or in ambient air. The analysis of the vapor fraction is performed separately, as described in Test Method D6562.  
1.2 Differential air sampling is performed with a segregating device. The aerosol fraction is collected on a polytetrafluoroethylene (PTFE) filter.  
1.3 The analysis of the aerosol fraction is performed by using a high performance liquid chromatograph (HPLC) equipped with an ultraviolet (UV) detector. An ultra high performance liquid chromatograph (UPLC) can also be used, provided that its performance is equivalent to what is stated in this standard. The range of application of the test method has been validated from 0.052 to 1.04 μg of monomeric HDI/mL, which corresponds, based on a 15 L air sample, to concentrations from 0.004 to 0.070 mg/m3 of HDI. Those concentrations correspond to a range of aerosol phase concentrations from 0.5 ppb (V) to 10 ppb (V) and cover the established threshold limit valve (TLV) value of 5 ppb (V).  
1.4 The quantification limit for the monomeric HDI is 0.041 μg per mL, which corresponds to 0.003 mg/m3 for a 15 L sampled air volume. This value is equivalent to ten times the standard deviation obtained from ten measurements carried out on a standard solution in contact with the PTFE filter whose concentration of 0.1 μg/mL is close to the expected detection limit.  
1.5 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.  
1.6 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety, health, and environmental practices and determine the applicability of regulatory limitations prior to use. See Section 9 for additional hazards.  
1.7 This intern...

General Information

• Status: Published
• Publication Date: 29-Feb-2020
• ICS: 13.040.30 - Workplace atmospheres
• Technical Committee: D22 - Air Quality
• Drafting Committee: D22.04 - Workplace Air Quality

Relations

• Replaces: ASTM D6561-06(2016) - Standard Test Method for Determination of Aerosol Monomeric and Oligomeric Hexamethylene Diisocyanate (HDl) in Air with (Methoxy-2–phenyl-1) Piperazine (MOPIP) in the Workplace
• Effective Date: 01-Mar-2020
• Refers: ASTM D1356-20a - Standard Terminology Relating to Sampling and Analysis of Atmospheres
• Effective Date: 01-Sep-2020
• Refers: ASTM D1356-20 - Standard Terminology Relating to Sampling and Analysis of Atmospheres
• Effective Date: 15-Mar-2020
• Refers: ASTM D6562-20 - Standard Test Method for Determination of Gaseous Hexamethylene Diisocyanate (HDI) in Air with 9-(N-methylaminomethyl) Anthracene Method (MAMA) in the Workplace
• Effective Date: 01-Mar-2020
• Refers: ASTM D1357-95(2019) - Standard Practice for Planning the Sampling of the Ambient Atmosphere
• Effective Date: 01-Aug-2019
• Refers: ASTM D4840-99(2018)e1 - Standard Guide for Sample Chain-of-Custody Procedures
• Effective Date: 15-Aug-2018
• Refers: ASTM D1356-15a - Standard Terminology Relating to Sampling and Analysis of Atmospheres
• Effective Date: 15-Oct-2015
• Refers: ASTM D1356-15 - Standard Terminology Relating to Sampling and Analysis of Atmospheres
• Effective Date: 01-Jul-2015
• Refers: ASTM D1356-14b - Standard Terminology Relating to Sampling and Analysis of Atmospheres
• Effective Date: 01-Dec-2014
• Refers: ASTM D1356-14a - Standard Terminology Relating to Sampling and Analysis of Atmospheres
• Effective Date: 01-May-2014
• Refers: ASTM D1356-14 - Standard Terminology Relating to Sampling and Analysis of Atmospheres
• Effective Date: 15-Jan-2014
• Refers: ASTM D6562-12 - Standard Test Method for Determination of Gaseous Hexamethylene Diisocyanate (HDI) in Air with 9-(N-methylaminomethyl) Anthracene Method (MAMA) in the Workplace
• Effective Date: 01-Apr-2012
• Refers: ASTM D5337-11 - Standard Practice for Flow Rate for Calibration of Personal Sampling Pumps
• Effective Date: 15-Nov-2011
• Refers: ASTM D1357-95(2011) - Standard Practice for Planning the Sampling of the Ambient Atmosphere
• Effective Date: 01-Oct-2011
• Refers: ASTM D6562-06(2011) - Standard Test Method for Determination of Gaseous Hexamethylene Diisocyanate (HDI) in Air with 9-(N-methylaminomethyl) Anthracene Method (MAMA) in the Workplace
• Effective Date: 01-Oct-2011

Overview

ASTM D6561-20 is the Standard Test Method for Determination of Aerosol Monomeric and Oligomeric Hexamethylene Diisocyanate (HDI) in Air with (Methoxy-2–phenyl-1) Piperazine (MOPIP) in the Workplace. Published by ASTM International, this standard is designed to measure levels of aerosol-phase HDI-which is widely used in the manufacture of paints-within workplace and ambient atmospheres.

Given the increasing industrial use of isocyanates, safeguarding worker health against HDI exposure is critical. ASTM D6561-20 outlines a reliable procedure for short-term exposure monitoring (15 minutes) of both monomeric and oligomeric HDI, using differential air sampling, PTFE filters, and high-performance liquid chromatography (HPLC) with UV detection. This method enables sensitive detection of HDI at concentrations relevant to occupational exposure limits, supporting both industrial hygiene and regulatory compliance.

Key Topics

• Purpose: To determine the concentration of aerosol HDI in workplace air samples, aiding in the evaluation and management of occupational exposure.
• Sampling Method: Utilizes a segregating device to collect separate aerosol and vapor fractions; aerosol is collected on a PTFE filter.
• Analysis: The PTFE filter is treated with (methoxy-2–phenyl-1) piperazine (MOPIP) and analyzed by HPLC with UV detection, allowing quantification of both monomeric and oligomeric HDI.
• Exposure Limits: The American Conference of Governmental Industrial Hygienists (ACGIH) sets a Threshold Limit Value (TLV) for monomeric HDI at 0.005 ppm (0.034 mg/m³); OSHA does not list a specific PEL for HDI.
• Sensitivity: The method is validated across concentrations from 0.004 to 0.070 mg/m³, covering critical occupational safety thresholds.
• Sample Volume and Stability: Requires only a 15 L air sample, with demonstrated stability for up to 14 days at room temperature or 42 days refrigerated.

Applications

• Occupational Air Monitoring: Used primarily for personal monitoring in industrial settings where HDI-based materials (such as paints and coatings) are handled or applied.
• Exposure Assessment: Supports compliance with exposure limits and helps identify necessary engineering or administrative controls to reduce HDI inhalation risks.
• Industrial Hygiene Programs: The method’s short sampling interval and low detection limit make it especially suitable for environments with rapid changes in HDI concentrations or short-duration tasks.
• Workplace Safety: Provides critical data for respiratory and health protection, addressing the risk of allergic sensitization, bronchitis, and acute respiratory effects from diisocyanate exposure.
• Ambient Air Quality Studies: Offers robust performance for both workplace and nearby ambient environments where emissions may present risks.

Related Standards

The following ASTM and consensus standards support or are referenced in conjunction with ASTM D6561-20:

• ASTM D6562: Test Method for Determination of Gaseous HDI in Air (for the vapor fraction)
• ASTM D1193: Specification for Reagent Water
• ASTM D1356: Terminology Relating to Sampling and Analysis of Atmospheres
• ASTM D4840: Guide for Sample Chain-of-Custody Procedures
• ASTM D5337: Practice for Flow Rate Adjustment of Personal Sampling Pumps

Other related guidance includes air contaminant sampling approaches and specific industrial hygiene protocols. Adopting ASTM D6561-20 helps organizations achieve accurate, traceable, and defensible data on HDI aerosol concentrations, which is crucial for worker safety programs and regulatory reporting.

Keywords: ASTM D6561-20, HDI monitoring, workplace air quality, isocyanate aerosol, industrial hygiene, personal exposure, air sampling, high-performance liquid chromatography, occupational safety, (methoxy-2–phenyl-1) piperazine, MOPIP.

Standards Content (Sample)

This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the
Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
Designation: D6561 − 20
Standard Test Method for
Determination of Aerosol Monomeric and Oligomeric
Hexamethylene Diisocyanate (HDl) in Air with (Methoxy-
2–phenyl-1) Piperazine (MOPIP) in the Workplace
This standard is issued under the fixed designation D6561; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision.Anumber in parentheses indicates the year of last reapproval.A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
1. Scope sampled air volume. This value is equivalent to ten times the
standarddeviationobtainedfromtenmeasurementscarriedout
1.1 This test method covers the determination of aerosol
on a standard solution in contact with the PTFE filter whose
hexamethylene diisocyanate (HDI) in air samples collected
concentration of 0.1 µg/mL is close to the expected detection
from workplace and ambient atmospheres. The method de-
limit.
scribed in this test method collects separate fractions. One
fractionwillbedominatedbyvapor,andtheotherfractionwill 1.5 The values stated in SI units are to be regarded as
be dominated by aerosol. The results obtained from the standard. No other units of measurement are included in this
analysis of the separate fractions do not necessarily represent standard.
the true partition of the measured HDI physical phases, and
1.6 This standard does not purport to address all of the
shouldonlybeconsideredarepresentationofthegeneraltrend
safety concerns, if any, associated with its use. It is the
in the physical phase partition within samples.The analyses of
responsibility of the user of this standard to establish appro-
the two fractions are different, and are provided in separate,
priate safety, health, and environmental practices and deter-
linked, standards to avoid confusion. This test method is
mine the applicability of regulatory limitations prior to use.
principally used to determine short term exposure (15 min) of
See Section 9 for additional hazards.
HDI in workplace environments for personal monitoring or in
1.7 This international standard was developed in accor-
ambient air. The analysis of the vapor fraction is performed
dance with internationally recognized principles on standard-
separately, as described in Test Method D6562.
ization established in the Decision on Principles for the
Development of International Standards, Guides and Recom-
1.2 Differential air sampling is performed with a segregat-
mendations issued by the World Trade Organization Technical
ing device.The aerosol fraction is collected on a polytetrafluo-
Barriers to Trade (TBT) Committee.
roethylene (PTFE) filter.
1.3 The analysis of the aerosol fraction is performed by
2. Referenced Documents
using a high performance liquid chromatograph (HPLC)
2.1 ASTM Standards:
equipped with an ultraviolet (UV) detector. An ultra high
D1193Specification for Reagent Water
performance liquid chromatograph (UPLC) can also be used,
D1356Terminology Relating to Sampling and Analysis of
provided that its performance is equivalent to what is stated in
Atmospheres
this standard. The range of application of the test method has
D1357Practice for Planning the Sampling of the Ambient
been validated from 0.052 to 1.04 µg of monomeric HDI/mL,
Atmosphere
which corresponds, based on a 15 L air sample, to concentra-
D4840Guide for Sample Chain-of-Custody Procedures
tionsfrom0.004to0.070mg/m ofHDI.Thoseconcentrations
D5337Practice for Flow RateAdjustment of Personal Sam-
correspondtoarangeofaerosolphaseconcentrationsfrom0.5
pling Pumps
ppb(V)to10ppb(V)andcovertheestablishedthresholdlimit
D6562Test Method for Determination of Gaseous Hexam-
valve (TLV) value of 5 ppb (V).
ethylene Diisocyanate (HDI) in Air with 9-(N-
1.4 ThequantificationlimitforthemonomericHDIis0.041
3 methylaminomethyl)Anthracene Method (MAMA) in the
µg per mL, which corresponds to 0.003 mg/m fora15L
Workplace
This test method is under the jurisdiction of ASTM Committee D22 on Air
Quality and is the direct responsibility of Subcommittee D22.04 on WorkplaceAir
Quality. For referenced ASTM standards, visit the ASTM website, www.astm.org, or
Current edition approved March 1, 2020. Published May 2020. Originally contact ASTM Customer Service at [e-mail]. For Annual Book of ASTM
approved in 2000. Last previous edition approved in 2016 as D6561–06 (2016). Standards volume information, refer to the standard’s Document Summary page on
DOI: 10.1520/D6561-20. the ASTM website.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
D6561 − 20
isocyanate against a standard, results from the two fractions
should be combined to give a single total value.
5.5 Due to its low LOD and low required volume (15 L),
thistestmethodiswellsuitedformonitoringofrespiratoryand
FIG. 1 MOPIP Solution
other problems related to diisocyanates and polyisocyanates.
Its short sampling times are compatible with the duration of
many industrial processes, and its low detection limit with the
3. Terminology
concentrations often found in the working area.
3.1 Definitions:
3.1.1 For definitions of terms used in this test method, refer
6. Interferences
to Terminology D1356.
6.1 Any substance, including strong oxidizing agents, that
can be deposited on the PTFE filter and react with MOPIP
4. Summary of Test Method
reagent can affect the analysis efficiency.
4.1 Vapor and aerosol fractions are sampled simultaneously
6.2 Any compound that has the same retention time as the
by using a segregating sampling device. The aerosols are
HDI-MOPIP derivative and contributes to UV response is an
collected on PTFE filter while the gaseous fraction is being
interference. Chromatographic conditions can sometimes be
adsorbed on a second filter made of glass fiber, impregnated
changed to eliminate an interference.
with a 9-(N-methylaminomethyl) anthracene (MAMA).
7. Apparatus
4.2 The analysis of the monomer in the gaseous fraction is
performed separately in accordance with the procedure de-
7.1 Sampling Equipment:
scribed in Test Method D6562.
7.1.1 Personal Sampling Pump, equipped with a flow-
monitoring device (rotameter, critical orifice) or a constant-
4.3 Immediately after sampling, the PTFE filter is trans-
flow device capable of drawing 1.0 L/min of air through the
ferred into a jar containing a (methoxy-2 phenyl-1) piperazine
sampling device for a period of at least 4 h.
(MOPIP) solution in toluene (1, 2). See Fig. 1.
7.1.2 Double Filter Sampling Device, 37 mm in diameter,
4.3.1 The solution is then evaporated to dryness and
three-piece personal monitor, plastic holder loaded with a
redissolved, using an acetic anhydride solution (see 8.11).
PTFE filter close to the mouth, followed by a glass fiber filter
Monomeric and oligomeric HDI are separated by using a
(GFF) impregnated with MAMA and a plastic back-up pad.
reversed phase HPLC column, and detection is made by using
The GFF is impregnated with an amount of MAMA in the
an HPLC equipped with UV detection. An ultra high perfor-
range from 0.07 to 0.25 mg.
mance liquid chromatograph (UPLC) can also be used, pro-
7.1.3 Flow Measuring Device, used in accordance with
videdthatitsperformanceisequivalenttowhatisstatedinthis
Practice D5337.
standard.
7.2 Analytical Equipment:
4.4 Concentration of monomeric and oligomeric diisocya-
7.2.1 Liquid Chromatograph, HPLC, equipped with a UV
nates contained in a sample is calculated by using an external
detector(242nmwavelength),connectedinserieswithadiode
standard of the monomeric HDI.
detector, and equipped with an automatic or manual sampling
portinjection.Anultrahighperformanceliquidchromatograph
5. Significance and Use
(UPLC) can also be used provided that the other equipment
5.1 HDI is mostly used in the preparation of paints.The use
mentioned below are adapted and offer at least the same
of isocyanates and their industrial needs have been in constant
performance stated in this standard.
growth.
7.2.2 Liquid Chromatographic Column, an HPLC stainless
5.2 Diisocyanates and polyisocyanates are irritants to skin,
steel column, capable of separating the urea derivatives. This
eyes, and mucous membranes. They are recognized to cause
test method recommends a 150 by 3.2 mm internal diameter
respiratory allergic sensitization, asthmatic bronchitis, and
stainlesssteelcolumnpackedwith3µmC-18,oranequivalent
acute respiratory intoxication (3-6).
column.
7.2.3 Electronic Integrator, or any other effective method
5.3 The American Conference of Governmental Industrial
for determining peak areas.
Hygienists (ACGIH) has adopted a threshold limit value–time
7.2.4 Analytical Balance, with a precision of 60.0001 g.
weighted average (TLV-TWA) of 0.005 ppm (V) or 0.034
7.2.5 Microsyringes and Pipets—Microsyringes are used in
mg/m for monomeric HDI (7). The Occupational Safety &
thepreparationofureaderivativesandstandards.Anautomatic
Health Administration of the U.S. Department of Labor
pipet, or any equivalent equipment, is required for sample
(OSHA) has not listed a permissible exposure limit (PEL) for
preparation.
HDI (8).
7.2.6 pH Meter, or any equivalent device capable of assay-
5.4 In any case, there are not separate exposure standards
ing a pH range between 2.5 and 7.
for vapor and aerosol. Therefore, in comparing the results for
7.2.7 Culture Tubes, 16 mm × 100 mm, disposable, in
borosilicate glass for evaporation of derivatized samples.
7.2.8 Glass Jars, 30 mL, and lids, capable of receiving 37
Theboldfacenumbersinparenthesesrefertothelistofreferencesattheendof
this standard. mm filters, used for derivatization of samples.
D6561 − 20
7.2.9 Vacuum Filtration System, filter 47 mm, with 0.22 µm 9. Hazards
pore size polyamide filters, or any equivalent method.
9.1 Warning—Diisocyanates are potentially hazardous
7.2.10 Syringe Operated Filter Unit, syringes with 4 mm,
chemicals and are extremely reactive. Refer to material safety
polyvinylidene fluoride 0.22-µm pore size filter unit, or any
data sheets for reagents.
equivalent device.
9.2 Warning—Avoid exposure to diisocyanate and sol-
7.2.11 Injection Vials, 1.5 mL vials with PTFE-coated
vents. Sample and standard preparations should be done in an
septums.
efficient operating hood. For remedial statement, see Ref (9).
7.2.12 Bottle—Amber colored bottle with cap and PTFE-
coated septum for conservation of stock and diluted standard
9.3 Warning—Wear safety glasses at all times and other
solutions of HDI. laboratory protective equipment if necessary.
7.2.13 Vacuum Evaporator, capable of heating to 55°C, or
9.4 Warning—Avoid skin contact with isocyanates and all
any equivalent device.
solvents.
7.2.14 Vortex Movement Mixer, or any equivalent device.
10. Sampling
8. Reagents and Materials
10.1 Refer to Practice D1357 for general information on
8.1 Purity of Reagents—Reagent grade chemicals shall be
sampling.
usedinalltests.Allreagentsshallconformtothespecifications
10.2 This test method recommends sampling in accordance
of the Committee on Analytical Reagents of the American
4 with the method described in Refs (9-11).
Chemical Society where such specifications are available.
10.3 Adjust the personal sampling pumps (see 7.1.1)tothe
Other grades may be used, provided it is first ascertained that
the reagent is of sufficiently high purity to permit its use recommended flow rate with an assembled cassette (see 7.1.2)
between the pump and the flow-measuring device in accor-
without lessening the accuracy of the determination.
dance to Practice D5337. After the sampling, perform a post
8.2 Purity of Water—Unlessotherwiseindicated,watershall
sampling flow rate verification. If the post sampling flow rate
be reagent water as defined by Type 2 of Specification D1193,
varies more than 65 % from the recommended flow rate,
HPLC grade.
invalidate the sample.
8.3 Acetic Acid, glacial (CH COOH), HPLC grade.
10.4 Equip the worker, whose exposure is to be evaluated,
8.4 Acetic Anhydride (CH CO) O), certified by American
3 2
with a filter holder connected to a belt-supported sampling
Chemical Society (ACS).
pump.Placethefilterholderpointingdownward,ifpossible,at
anoptimumangleof45°fromhorizontalinthebreathingzone
8.5 Acetonitrile, HPLC grade.
of the worker. Draw air through the sampling device, and
8.6 Buffer—In a 1-L volumetric flask, dissolve 1 g sodium
collect 15 L at a rate of approximately 1.0 L/mi
...

This document is not an ASTM standard and is intended only to provide the user of an ASTM standard an indication of what changes have been made to the previous version. Because
it may not be technically possible to adequately depict all changes accurately, ASTM recommends that users consult prior editions as appropriate. In all cases only the current version
of the standard as published by ASTM is to be considered the official document.
Designation: D6561 − 06 (Reapproved 2016) D6561 − 20
Standard Test Method for
Determination of Aerosol Monomeric and Oligomeric
Hexamethylene Diisocyanate (HDl) in Air with (Methoxy-
2–phenyl-1) Piperazine (MOPIP) in the Workplace
This standard is issued under the fixed designation D6561; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
1. Scope
1.1 This test method covers the determination of aerosol hexamethylene diisocyanate (HDI) in air samples collected from
workplace and ambient atmospheres. The method described in this test method collects separate fractions. One fraction will be
dominated by vapor, and the other fraction will be dominated by aerosol. It is not known at the present time whether this represents
a perfect separation of vapor and aerosol, and in any case, there are not separate exposure standards for vapor and aerosol.
Therefore, in comparing the results for isocyanate against a standard, results from the two fractions should be combined to give
a single total value. The reason for splitting the sample into two fractions is to increase analytic sensitivity for the vapor fraction
and also to give the hygienist or ventilation engineer some information concerning the likely state of the isocyanate species. The
results obtained from the analysis of the separate fractions do not necessarily represent the true partition of the measured HDI
physical phases, and should only be considered a representation of the general trend in the physical phase partition within samples.
The analyses of the two fractions are different, and are provided in separate, linked, standards to avoid confusion. This test method
is principally used to determine short term exposure (15 min) of HDI in workplace environments for personal monitoring or in
ambient air. The analysis of the vapor fraction is performed separately, as described in Test Method D6562.
1.2 Differential air sampling is performed with a segregating device. The aerosol fraction is collected on a polytetrafluoroeth-
ylene (PTFE) filter.
1.3 Immediately after sampling, the PTFE filter is transferred into a jar containing a (methoxy-2 phenyl-1) piperazine (MOPIP)
solution in toluene.
1.3 The analysis of the aerosol fraction is performed by using a high performance liquid chromatograph (HPLC) equipped with
an ultraviolet (UV) detector. An ultra high performance liquid chromatograph (UPLC) can also be used, provided that its
performance is equivalent to what is stated in this standard. The range of application of the test method has been validated from
0.052 to 1.04 μg of monomeric HDI/mL, which corresponds, based on a 15 L air sample, to concentrations from 0.004 to 0.070
mg/m of HDI. Those concentrations correspond to a range of aerosol phase concentrations from 0.5 ppb (V) to 10 ppb (V) and
cover the established threshold limit valve (TLV) value of 5 ppb (V).
1.4 The quantification limit for the monomeric HDI is 0.041 μg per mL, which corresponds to 0.003 mg/m for a 15 L sampled
air volume. This value is equivalent to ten times the standard deviation obtained from ten measurements carried out on a standard
solution in contact with the PTFE filter whose concentration of 0.1 μg/mL is close to the expected detection limit.
1.5 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.
1.6 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility
of the user of this standard to establish appropriate safety safety, health, and healthenvironmental practices and determine the
applicability of regulatory limitations prior to use. See Section 9 for additional hazards.
1.7 This international standard was developed in accordance with internationally recognized principles on standardization
established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued
by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
This test method is under the jurisdiction of ASTM Committee D22 on Air Quality and is the direct responsibility of Subcommittee D22.04 on Workplace Air Quality.
Current edition approved Nov. 1, 2016March 1, 2020. Published November 2016May 2020. Originally approved in 2000. Last previous edition approved in 20112016 as
D6561 – 06 (2011).(2016). DOI: 10.1520/D6561-06R16.10.1520/D6561-20.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
D6561 − 20
FIG. 1 MOPIP Solution
2. Referenced Documents
2.1 ASTM Standards:
D1193 Specification for Reagent Water
D1356 Terminology Relating to Sampling and Analysis of Atmospheres
D1357 Practice for Planning the Sampling of the Ambient Atmosphere
D4840 Guide for Sample Chain-of-Custody Procedures
D5337 Practice for Flow Rate Adjustment of Personal Sampling Pumps
D6562 Test Method for Determination of Gaseous Hexamethylene Diisocyanate (HDI) in Air with 9-(N-methylaminomethyl)
Anthracene Method (MAMA) in the Workplace
2.2 Other Standard:
Sampling Guide for Air Contaminants in the Workplace
3. Terminology
3.1 Definitions:
3.1.1 For definitions of terms used in this test method, refer to Terminology D1356.
4. Summary of Test Method
4.1 Vapor and aerosol fractions are sampled simultaneously by using a segregating sampling device. The aerosols are collected
on PTFE filter while the gaseous fraction is being adsorbed on a second filter made of glass fiber, impregnated with a
9-(N-methylaminomethyl) anthracene (MAMA).
4.2 The analysis of the monomer in the gaseous fraction is performed separately in accordance with the procedure described
in Test Method D6562.
4.3 Diisocyanates present as aerosols are collected on Immediately after sampling, the PTFE filter and derivatized in a MOPIP
solution is transferred into a jar containing a (methoxy-2 phenyl-1) piperazine (MOPIP) solution in toluene (1, 2). See Fig. 1.
4.3.1 The solution is then evaporated to dryness and redissolved, using thean acetic anhydride solution (see 8.11). Monomeric
and oligomeric HDI are separated by using a reversed phase HPLC column, and detection is made by using an HPLC equipped
with UV detection. An ultra high performance liquid chromatograph (UPLC) can also be used, provided that its performance is
equivalent to what is stated in this standard.
4.4 Concentration of monomeric and oligomeric diisocyanates contained in a sample is calculated by using an external standard
of the monomeric HDI.
5. Significance and Use
5.1 HDI is mostly used in the preparation of paints. For the last ten years, the The use of isocyanates and their industrial needs
have been in constant growth.
5.2 Diisocyanates and polyisocyanates are irritants to skin, eyes, and mucous membranes. They are recognized to cause
respiratory allergic sensitization, asthmatic bronchitis, and acute respiratory intoxication (3-6).
5.3 The American Conference of Governmental Industrial Hygienists (ACGIH) has adopted a threshold limit value - time
value–time weighted average (TLV – TWA) (TLV-TWA) of 0.005 ppm (V) or 0.034 mg/m for monomeric HDI (7). The
Occupational Safety & Health Administration of the U.S. Department of Labor (OSHA) has not listed a permissible exposure limit
(PEL) for HDI (8).
5.4 In any case, there are not separate exposure standards for vapor and aerosol. Therefore, in comparing the results for
isocyanate against a standard, results from the two fractions should be combined to give a single total value.
5.5 Due to its low LOD and low required volume (15 L), this test method is well suited for monitoring of respiratory and other
problems related to diisocyanates and polyisocyanates. Its short sampling times are compatible with the duration of many industrial
processes, and its low detection limit with the concentrations often found in the working area.
For referenced ASTM standards, visit the ASTM website, www.astm.org, or contact ASTM Customer Service at [e-mail]. For Annual Book of ASTM Standards
volume information, refer to the standard’s Document Summary page on the ASTM website.
The boldface numbers in parentheses refer to the list of references at the end of this standard.
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6. Interferences
6.1 Any substance, including strong oxidizing agents, that can be deposited on the PTFE filter and react with MOPIP reagent
can affect the analysis efficiency.
6.2 Any compound that has the same retention time as the HDI-MOPIP derivative and contributes to UV response is an
interference. Chromatographic conditions can sometimes be changed to eliminate an interference.
7. Apparatus
7.1 Sampling Equipment:
7.1.1 Personal Sampling Pump, equipped with a flow-monitoring device (rotameter, critical orifice) or a constant-flow device
capable of drawing 1.0 L/min of air through the sampling device for a period of at least 4 h.
7.1.2 Double Filter Sampling Device, 37 mm in diameter, three-piece personal monitor, plastic holder loaded with a PTFE filter
close to the mouth, followed by a glass fiber filter (GFF) impregnated with MAMA and a plastic back-up pad. The GFF is
impregnated with an amount of MAMA in the range from 0.07 to 0.25 mg.
7.1.3 Flow Measuring Device, used in accordance with Practice D5337.
7.2 Analytical Equipment:
7.2.1 Liquid Chromatograph, HPLC, equipped with a UV detector (242 nm wavelength), connected in series with a diode
detector, and equipped with an automatic or manual sampling port injection. An ultra high performance liquid chromatograph
(UPLC) can also be used provided that the other equipment mentioned below are adapted and offer at least the same performance
stated in this standard.
7.2.2 Liquid Chromatographic Column, an HPLC stainless steel column, capable of separating the urea derivatives. This test
method recommends a 150 by 3.2-mm 3.2 mm internal diameter stainless steel column packed with 3 μm C-18, or an equivalent
column.
7.2.3 Electronic Integrator, or any other effective method for determining peak areas.
7.2.4 Analytical Balance, with a precision of 60.0001 g.
7.2.5 Microsyringes and Pipets—Microsyringes are used in the preparation of urea derivatives and standards. An automatic
pipet, or any equivalent equipment, is required for sample preparation.
7.2.6 pH Meter, or any equivalent device capable of assaying a pH range between 2.5 and 7.
7.2.7 Culture Tubes, 16 by mm × 100 mm, disposable, in borosilicate glass for evaporation of derivatized samples.
7.2.8 Glass Jars, 30 mL, and lids, capable of receiving 37-mm 37 mm filters, used for derivatization of samples.
7.2.9 Vacuum Filtration System, filter 47 mm, with 0.22-μm 0.22 μm pore size polyamide filters, or any equivalent method.
7.2.10 Syringe Operated Filter Unit, syringes with 4 mm, polyvinylidene fluoride 0.22-μm pore size filter unit, or any equivalent
device.
7.2.11 Injection Vials, 1.5-mL 1.5 mL vials with PTFE-coated septums.
7.2.12 Bottle, Bottle—amberAmber colored bottle with cap and PTFE-coated septum for conservation of stock and diluted
standard solutions of HDI.
7.2.13 Vacuum Evaporator, capable of heating to 55°C, or any equivalent device.
7.2.14 Vortex Movement Mixer, or any equivalent device.
8. Reagents and Materials
8.1 Purity of Reagents—Reagent grade chemicals shall be used in all tests. All reagents shall conform to the specifications of
the Committee on Analytical Reagents of the American Chemical Society where such specifications are available. Other grades
may be used, provided it is first ascertained that the reagent is of sufficiently high purity to permit its use without lessening the
accuracy of the determination.
8.2 Purity of Water—Unless otherwise indicated, water shall be reagent water as defined by Type 2 of Specification D1193,
HPLC grade.
8.3 Acetic Acid, glacial (CH COOH), HPLC grade.
8.4 Acetic Anhydride (CH CO) O), certified by American Chemical Society (ACS).
3 2
8.5 Acetonitrile, HPLC grade.
8.6 Buffer—In a 1-L volumetric flask, dissolve 12.51 g sodium acetate (NaC H O ) (see 8.12) in water and dilute to volume.
2 3 2
Add glacial acetic acid (CH COOH) (see 8.11) to acidify to pH = 6.0. Under vacuum, filter the buffer with a 0.22-μm pore size
filter.
Reagent Chemicals, American Chemical Society Specifications,ACS Reagent Chemicals, Specifications and Procedures for Reagents and Standard-Grade Reference
Materials, American Chemical Society, Washington, D.C.DC. For suggestions on the testing of reagents not listed by the American Chemical Society, see Analar Standards
for Laboratory Chemicals, BDH Ltd., Poole, Dorset, U.K., and the United States Pharmacopeia and National Formulary, U.S. Pharmacopeial Convention, Inc. (USPC),
Rockville, MD.
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8.7 Derivatization Solution—Weigh 50 mg of MOPIP (see 8.9), and dilute to 500 mL in a volumetric flask with toluene (see
8.13). This solution is equivalent to 0.1 mg MOPIP/mL.
8.8 Hexamethylene Diisocyanate (HDI), (F.W. 168), 98 % purity.
8.9 (Methoxy-2-phenyl-1) Piperazine (MOPIP), (F.W. 192.2). 98 % purity.
8.10 Mobile Phase, a solvent mixture of 60 % (v/v) acetonitrile (see 8.5) and 40 % (v/v) buffer (see 8.6).
8.11 Redissolution Solution—Dilute 500 μL of acetic anhydride ( (CH((CH CO) O) (see 8.4) to 100 mL with acetonitrile (see
3 2
8.5).
8.12 Sodium Acetate (NaC H O ),). certified ACS.
2 3 2
8.13 Toluene, HPLC grade.
9. Hazards
9.1 Warning—Diisocyanates are potentially hazardous chemicals and are extremely reactive. Refer to material safety data
sheets for reagents.
9.2 Warning—Avoid exposure to diisocyanate and solvents. Sample and standard preparations should be done in an efficient
operating hood. For remedial statement, see
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