SIST ISO 19087:2019
Workplace air - Analysis of respirable crystalline silica by Fourier-Transform Infrared spectroscopy
Workplace air - Analysis of respirable crystalline silica by Fourier-Transform Infrared spectroscopy
This document is a standard for the analysis by Fourier-Transform Infrared (FTIR) of respirable
crystalline silica (RCS) in samples of air collected on collection substrates (i.e. filters or foams). Three
analytical approaches are described for whom the dust from the sample collection substrate is
a) analysed directly on sampled filter,
b) recovered, treated and deposited onto another filter for analysis, or
c) recovered, treated and pressed into a potassium bromide (KBr) pellet for analysis.
This document provides information on the instrumental parameters, the sensitivity of different
sampling apparatus, the use of different filters and sample treatment to remove interference. In this
document the expression RCS includes the most common polymorphs quartz and cristobalite.
This document excludes the less common polymorphs of crystalline silica, such as tridymite.
Under certain circumstances (i.e. low filter dust loads, low silica content), the analytical approach
described in this method cannot fulfil the expanded uncertainty requirements of ISO 20581. Guidance
for calculation of uncertainty for measurements of RCS is given in ISO 24095.
Air des lieux de travail - Mesure de la fraction alvéolaire de la silice cristalline par spectrométrie infrarouge
Zrak na delovnem mestu - Analiza respirabilnega kristaliničnega kremena z infrardečo spektroskopijo s Fourierjevo transformacijo (FTIR)
Ta dokument je standard za analizo z infrardečo spektroskopijo s Fourierjevo transformacijo (FTIR) respirabilnega kristalnega kremena (RCS) v vzorcih zraka, zbranih na zbirnih podlagah (filtrih ali penah). Opisani so trije analitični pristopi, pri katerih se prah z vzorčne zbirne podlage
a) analizira neposredno s filtra z vzorcem,
b) zbere, obdela in odloži na drugem filtru za analizo,
c) zbere, obdela in vtisne v pelet iz kalijevega bromida (KBr) za analizo.
Ta dokument podaja informacije o instrumentalnih parametrih, občutljivosti različnih naprav za vzorčenje, uporabi različnih filtrov in vzorčni obdelavi za odstranjevanje motenj. V tem dokumentu izraz RCS vključuje najpogostejši polimorfni kremen in kristobalit. Ta dokument ne zajema manj pogostih oblik kristalnega kremena, kot je tridimit.
Pod določenimi pogoji (majhne količine prahu filtra, majhna vsebnost kremena) analitični pristop, opisan v tej metodi, ne more izpolnjevati razširjenih zahtev negotovosti standarda ISO 20581. Vodilo za izračun negotovosti meritev RCS je podano v standardu ISO 24095.
General Information
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Standards Content (Sample)
INTERNATIONAL ISO
STANDARD 19087
First edition
2018-07
Workplace air — Analysis of
respirable crystalline silica by Fourier-
Transform Infrared spectroscopy
Air des lieux de travail — Mesure de la fraction alvéolaire de la silice
cristalline par spectrométrie infrarouge
Reference number
ISO 19087:2018(E)
©
ISO 2018
---------------------- Page: 1 ----------------------
ISO 19087:2018(E)
COPYRIGHT PROTECTED DOCUMENT
© ISO 2018
All rights reserved. Unless otherwise specified, or required in the context of its implementation, no part of this publication may
be reproduced or utilized otherwise in any form or by any means, electronic or mechanical, including photocopying, or posting
on the internet or an intranet, without prior written permission. Permission can be requested from either ISO at the address
below or ISO’s member body in the country of the requester.
ISO copyright office
CP 401 • Ch. de Blandonnet 8
CH-1214 Vernier, Geneva
Phone: +41 22 749 01 11
Fax: +41 22 749 09 47
Email: copyright@iso.org
Website: www.iso.org
Published in Switzerland
ii © ISO 2018 – All rights reserved
---------------------- Page: 2 ----------------------
ISO 19087:2018(E)
Contents Page
Foreword .v
Introduction .vi
1 Scope . 1
2 Normative reference . 1
3 Terms and definitions . 1
4 Principle . 2
5 Apparatus, equipment and reagents . 3
6 Sampling . 7
6.1 Sample collection . 7
6.2 Transport . 8
7 Preparation . 9
7.1 Preparation of calibration samples . 9
7.1.1 Preparation of direct-on-filter calibration samples . . 9
7.1.2 Preparation of redeposition calibration samples .10
7.1.3 Preparation of KBr pellet calibration samples .10
7.2 Preparation of the collection substrate for indirect analysis .11
7.2.1 PVC, MCE and polycarbonate filters .11
7.2.2 Cellulose nitrate filters .12
7.2.3 Polyurethane foams . .12
7.3 Redeposition onto analysis filter .13
7.3.1 Crucibles from the furnace .13
7.3.2 Bottles or beakers from a plasma asher .13
7.4 Preparation of KBr pellets .14
8 Analytical procedure .14
8.1 Gravimetric analysis for respirable dust .14
8.2 Fourier-Transform Infrared analysis .15
8.2.1 Background correction .15
8.2.2 Measurement .15
8.3 Calibration .15
9 Evaluation of Fourier-Transform Infrared spectra .17
9.1 General aspects .17
9.2 RCS quantification using peak height .17
9.3 RCS quantification using peak integral .18
[12][14]
9.3.1 Determination of the absorption in the range of the analytical bands .18
[20]
9.3.2 Subtraction of a reference spectrum .18
9.3.3 Other evaluation methods .20
9.4 Interferences .20
10 Calculation of results .20
10.1 Concentration of RCS .20
11 Performance characteristics .21
11.1 Limit of detection .21
11.2 Limits of quantification .21
11.3 Uncertainty .21
11.4 Differences between samplers .21
12 Test report .22
Annex A (normative) Sample treatment strategies for the removal of interferences .23
Annex B (informative) Differences between samplers (cyclones and other types) .24
Annex C (informative) .26
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ISO 19087:2018(E)
Annex D (normative) Examples of dust collection substrates and analysis filters .28
Bibliography .29
iv © ISO 2018 – All rights reserved
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ISO 19087:2018(E)
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).
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. Details of
any patent rights identified during the development of the document will be in the Introduction and/or
on the ISO list of patent declarations received (see www .iso .org/patents).
Any trade name used in this document is information given for the convenience of users and does not
constitute an endorsement.
For an explanation on 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 the following
URL: www .iso .org/iso/foreword .html.
This document was prepared by Technical Committee ISO/TC 146, Air quality, Subcommittee SC 2,
Workplace air.
© ISO 2018 – All rights reserved v
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ISO 19087:2018(E)
Introduction
Respirable crystalline silica (RCS) is a hazard to the health of workers in many industries through
exposure by inhalation. Industrial hygienists and other public health professionals need to determine
the effectiveness of measures taken to control workers’ exposure. The collection of samples of air
during a work activity and then measuring the amount of respirable crystalline silica are often done to
assess an individual’s exposure, their respiratory protection, or the effectiveness of controls. Fourier-
Transform Infrared (FTIR) analysis of crystalline silica in a sample of respirable dust collected on a
collection substrate is employed in many countries to measure and estimate exposure to RCS. FTIR is
able to measure quartz and cristobalite.
This document specifies the analysis procedures for the measurement of RCS through three methods:
a) Direct-on-filter method: a method of analysing RCS directly on the air sample filter. A specific
requirement of this method is that the sampler used for the workplace measurements is the same
as that used for the preparation of calibration samples.
b) Indirect method by redeposition: a method whereby the dust is recovered from the collection
substrate and deposited onto a filter for analysis.
c) Indirect method by potassium bromide (KBr) pellet: a method whereby the dust is recovered from
the collection substrate and pressed into a potassium bromide (KBr) pellet for analysis.
Many different types of sampling apparatus are used to collect respirable dust, according to the
occupational hygiene convention. This document is designed to accommodate the variety of samplers
and collection substrates available to analysts. This document is used in conjunction with ISO 24095
which promotes best practice for these analyses.
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INTERNATIONAL STANDARD ISO 19087:2018(E)
Workplace air — Analysis of respirable crystalline silica by
Fourier-Transform Infrared spectroscopy
1 Scope
This document is a standard for the analysis by Fourier-Transform Infrared (FTIR) of respirable
crystalline silica (RCS) in samples of air collected on collection substrates (i.e. filters or foams). Three
analytical approaches are described for whom the dust from the sample collection substrate is
a) analysed directly on sampled filter,
b) recovered, treated and deposited onto another filter for analysis, or
c) recovered, treated and pressed into a potassium bromide (KBr) pellet for analysis.
This document provides information on the instrumental parameters, the sensitivity of different
sampling apparatus, the use of different filters and sample treatment to remove interference. In this
document the expression RCS includes the most common polymorphs quartz and cristobalite.
This document excludes the less common polymorphs of crystalline silica, such as tridymite.
Under certain circumstances (i.e. low filter dust loads, low silica content), the analytical approach
described in this method cannot fulfil the expanded uncertainty requirements of ISO 20581. Guidance
for calculation of uncertainty for measurements of RCS is given in ISO 24095.
2 Normative reference
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 7708, Air quality — Particle size fraction definitions for health-related sampling
ISO 13137, Workplace atmospheres — Pumps for personal sampling of chemical and biological agents —
Requirements and test methods
EN 13205, Workplace exposure — Assessment ofsampler performance for measurement of airborne
particle concentrations
ISO 15767, Workplace atmospheres — Controlling and characterizing uncertainty in weighing collected
aerosols
ISO 18158, Workplace air — Terminology
ISO 24095, Workplace air — Guidance for the measurement of respirable crystalline silica
3 Terms and definitions
For the purposes of this document, the terms and definitions given in ISO 18158 and the following apply.
ISO and IEC maintain terminological databases for use in standardization at the following addresses:
— ISO Online browsing platform: available at https: //www .iso .org/obp
— IEC Electropedia: available at http: //www .electropedia .org/
© ISO 2018 – All rights reserved 1
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ISO 19087:2018(E)
3.1 General definitions
3.1.1
respirable crystalline silica
RCS
inhaled particles of crystalline silica that penetrate into the unciliated airways according to the
respirable convention described in ISO 7708
3.2 Sampling definitions
3.2.1
analysis filter
suitable filter used to carry out the RCS analysis
Note 1 to entry: For direct-on-filter FTIR analysis the collection substrate is the analysis filter.
Note 2 to entry: For the indirect analysis the dust is removed from the collection substrate and redeposited onto
an analysis filter.
3.2.2
collection substrate
medium on which airborne chemical and/or biological agents are collected for subsequent analysis
Note 1 to entry: For the purpose of this document, filters, polyurethane foams and sampling cassettes are
examples of collection substrates for airborne particles.
4 Principle
This document provides three Fourier-Transform Infrared (FTIR) analytical approaches for the analysis
of RCS in respirable dust collected on a sample collection substrate.
a) Direct-on-filter method:
The respirable dust on the collection substrate (usually a 25 mm diameter filter) is measured
without transferring the dust to an analysis filter. The mass of RCS is determined from the FTIR
response, calibrated against filters loaded with known amounts of RCS reference material.
b) Indirect method (redeposition):
The dust from the sample collection substrate (i.e. a 37 mm diameter filter or a polyurethane
foam) is recovered, treated and deposited on another analysis filter (usually 25 mm diameter or
smaller) for analysis by the instrument. The instrument is calibrated by preparing test samples
from aliquots of a suspension of a reference material. The mass of RCS is determined from the FTIR
response, calibrated against analysis filters loaded with known amounts of RCS reference material.
c) Indirect method (KBr pellet):
The dust from the sample collection substrate (i.e. a 37 mm diameter filter or a polyurethane foam)
is recovered, treated and pressed into a KBr pellet for analysis by the instrument. The instrument
is calibrated by preparing KBr pellets with known amounts of a reference material. The mass of
RCS is determined from the FTIR response, calibrated against pellets loaded with known amounts
of RCS reference material.
Since the volume of air sampled is known, the concentration of RCS in the air is readily calculated.
Because the different aerosol samplers for respirable dust deposit the sample over the surface of the
filter in different ways, the FTIR instruments used for the direct-on-filter analysis approach shall be
calibrated for the aerosol sampler used to collect the samples.
The suitability of FTIR to determine the RCS concentration in a workplace sample depends on the
composition of the dust and potential interferences. If the FTIR method to subtract a reference
spectrum from the sample spectrum (refer to 9.3.2) does not lead to a satisfactory baseline profile, then
2 © ISO 2018 – All rights reserved
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ISO 19087:2018(E)
the FTIR method is not suitable for the matrix and quantitative FTIR analysis cannot be carried out. As
an alternative XRD analytical method should be used. Qualitative X-ray diffraction (XRD) analysis can
be carried out prior to FTIR analysis to obtain information about the sample.
5 Apparatus, equipment and reagents
5.1 Sampling equipment
5.1.1 Samplers.
5.1.1.1 The particle size-selection performance of the samplers used shall match the criteria for
respirable dust as specified in ISO 7708 according to the test protocol in EN 13205-2.
5.1.1.2 Samplers using a filter or foam pad are suitable for this method.
NOTE Annex B provides information on the performance of different personal respirable samplers that are
currently in use.
NOTE Foam pads and silver membrane filters are not suitable for direct-on-filter method.
5.1.1.3 Cassettes holding filters shall be made of conductive material.
5.1.1.4 Each sampler should be labelled with a unique number, in order to identify samplers that start
to underperform after long-term use.
5.1.1.5 Samplers (sampling train) shall comply with the requirements for calibration in ISO 13137.
NOTE In some countries there can be exceptions due to national regulations.
5.1.2 Collection substrates and analysis filters.
5.1.2.1 Filters as collection substrates shall be of a diameter suitable for use in the selected sampler
and have a capture efficiency for respirable particles as specified in ISO 24095.
5.1.2.2 It is important for the analyst to know the composition of the collection substrate used to
collect the sample since it has a direct bearing on the analytical approach used. The collection substrates
generally used for the sampling of RCS, and their characteristics, are listed in Annex D.
NOTE Additional information about choice of filter material for quartz measurement in coal mine dust can
be found in Reference [24].
5.1.2.3 Filter materials listed in Annex D generally do not contain compounds that interfere with the
measurement of quartz and cristobalite. Impurities can be introduced during the filter manufacturing
process and background absorbance can increase depending on filter material. Therefore, batches of
filters should be regularly tested to detect potential interferences and background levels.
5.1.2.4 Variable background has an effect on the readability of absorbance spectra, increasing the
limit of detection for RCS. PVC and polypropylene used as analysis filters exhibit the least variability and
lowest background levels and thus are useful in situations where low limits of detection are required.
5.1.2.5 Weighing, if required, should be performed following ISO 15767 (see 8.1). Filters shall not be
[18]
weighed in cassettes as large weight variations have been reported . Reference shall be made to the
instructions of the collection substrate manufacturer.
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ISO 19087:2018(E)
5.1.2.7 An important property for an analysis filter is that it is transparent to infrared and provides a
relatively low background variation near the absorbance for crystalline silica.
5.1.3 Sampling pumps.
Sampling pumps shall comply with the requirements of ISO 13137.
5.1.4 Flow meters.
Flow meters shall comply with the requirements of ISO 13137.
5.1.5 Other equipment required.
Other equipment required for sampling includes the following:
a) belts or harnesses to which the sampling pumps can conveniently be fixed;
b) flexible tubing, to connect the sampler to the sampling pump;
c) a means to transport the samples from the workplace to the laboratory, which minimises the
possibility of accidental transfers of collected dust to or from the collection substrate (filter or
foam). Transportation will usually require caps or covers for the samplers, filter cassettes or other
substrates, as detailed in the manufacturer’s instructions for use of the instruments;
d) a thermometer (readable to 1 °C) and a barometer (readable to 0,1 kPa), to measure atmospheric
temperature and pressure for flow rate correction, when the temperature and pressure at the time
of use differ from the conditions under which the flow meter was calibrated (ISO 24095).
5.2 Equipment for calibration
5.2.1 Dust cloud generator (needed for direct-on-filter analysis).
A device to generate atmospheres of reference material and contain them is needed when following
the direct-on-filter analytical approach. An example of such a device is given in Figure 1. This device is
constructed from borosilicate glass with a lid made from acrylic glass. An aerosol of dust is generated
into the upper cylindrical chamber by applying a short burst of pressurized air to a dust contained in a
bowl at the bottom. Sampling equipment shall be prepared following 6.1.1 to 6.1.6 and 6.1.9. Samplers
are fitted at the top of the device. To avoid agglomerations and charge interactions between the dust
and the filter inside the aerosol sampler it is recommended that the device be earthed (grounded).
NOTE An Aerosol generation device can also be useful for preparing samples for indirect FTIR methods.
4 © ISO 2018 – All rights reserved
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ISO 19087:2018(E)
Dimensions in centimetre
Key
1 acrylic glass lid
2 holes for cyclone samplers
3 B29/32 cone and socket joint
4 bowl for sample
5 orifice diameter 1 mm
6 compressed air at approximately 50 psi
Figure 1 — Example of an aerosol generation apparatus
5.2.2 Laboratory equipment to prepare suspensions.
For the preparation of calibration samples, suspensions with a defined content of quartz dust can be
used. Volumetric flasks of 100 mL and 250 mL, a bath thermostat with a built-in cooling coil, working
temperature range shall include 20 °C, microlitre pipettes of variable volumes, with a range of between
50 µL and 1 000 µL, an Erlenmeyer flask and a magnetic stirrer.
5.3 Equipment for the determination of dust concentration
5.3.1 Balance.
Weighing should be performed according to ISO 15767. For the preparation of low masses of calibration
samples, a microbalance capable of weighing ±1 µg (or better) is required. An electrostatic eliminator
is needed when weighing collection substrates. For the weighing of foams from the CIP 10-R sampler
for example a balance with an analytical sensitivity of 10 µg with an operational range of 0 g to 20 g is
required.
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ISO 19087:2018(E)
5.4 Equipment for sample preparation
5.4.1 Redeposition laboratory equipment.
Platinum or glazed ceramic crucibles, beakers, tongs, calibrated pipettes, ultrasonic bath, magnetic
stirrer, apparatus to filter a sample onto a 25-mm diameter filter, a pump to generate vacuum, and a
fume cupboard to contain dusts, vapours and gases.
5.4.2 KBr pellet laboratory equipment.
Platinum or glazed ceramic crucibles, tongs, a pump to generate vacuum, a boron carbide mortar and
pestle, a 50-mm agate or metal microspatula, a laboratory press for preparing KBr pellets, a KBr pellet
evacuable die (typically 13 mm), a pump to generate vacuum, a desiccator with silica gel desiccant, a
hair brush with anti-static effects (e.g. badger or camel hair) and glassine paper.
5.4.3 Equipment to recover dust from the collection substrate.
A furnace capable of operating at a minimum of 600 °C or a low temperature plasma asher to remove
the filter membrane. Tetrahydrofuran (THF) can be used for the dissolution of PVC filters instead of a
plasma asher or furnace.
NOTE To remove interfering substances temperatures of up to 1 000 °C may be required. To prevent
reactions occurring between silica and calcium carbonate at high temperatures, the latter may be removed by
washing with hydrochloric acid (5.6.2.3).
5.5 Equipment for analysis
5.5.1 Spectrometer.
−1 −1 −1
A FTIR spectrometer with a wavelength range from at least 4 000 cm to 400 cm and 4 cm
resolution or better. A suitable sample holder (e.g. a rotatable polarizer mount) is required so that the
sample can be rotated in its own plane. This will enable the effect of non-uniform sample deposition
to be reduced by taking absorbance measurements at several orientations. If the infrared beam in the
instrument has a circular cross-section, rotation is not required.
5.6 Reagents
5.6.1 Direct-on-filter reagents.
Reagents are not normally required for the direct-on-filter analysis method.
5.6.2 Redeposition reagents.
5.6.2.1 Suspension.
Deionised water.
2-Propanol.
Ethanol.
5.6.2.2 Filter dissolution.
Tetrahydrofuran (THF).
1,3-Butanediol, if using cellulose nitrate air sample filters.
6 © ISO 2018 – All rights reserved
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ISO 19087:2018(E)
5.6.2.3 Removal of interferences.
Hydrochloric acid, 0,1 N to 1 N.
5.6.3 KBr pellet reagents.
Potassium bromide (KBr), infrared quality (stored in a desiccator)
1,3-Butanediol
Hydrochloric acid, 0,1 N to 1 N
Sodium hydroxide (2 N)
5.6.4 Reference materials.
It is important to use a reference material in which the purity and crystalline content is well
characterized. The material used for calibration shall conform to the recommendations in ISO 24095.
NOTE The United States National Institute of Science and Technology (NIST) have developed Standard
Reference Materials (SRM) for respirable quartz (1878 series) and for respirable cristobalite (1879 series).
NOTE A comparison of the crystallinity of calibration
...
SLOVENSKI STANDARD
SIST ISO 19087:2019
01-september-2019
Zrak na delovnem mestu - Analiza respirabilnega kristaliničnega kremena z
infrardečo spektroskopijo s Fourierjevo transformacijo (FTIR)
Workplace air - Analysis of respirable crystalline silica by Fourier-Transform Infrared
spectroscopy
Air des lieux de travail - Mesure de la fraction alvéolaire de la silice cristalline par
spectrométrie infrarouge
Ta slovenski standard je istoveten z: ISO 19087:2018
ICS:
13.040.30 Kakovost zraka na delovnem Workplace atmospheres
mestu
SIST ISO 19087:2019 en
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.
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SIST ISO 19087:2019
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SIST ISO 19087:2019
INTERNATIONAL ISO
STANDARD 19087
First edition
2018-07
Workplace air — Analysis of
respirable crystalline silica by Fourier-
Transform Infrared spectroscopy
Air des lieux de travail — Mesure de la fraction alvéolaire de la silice
cristalline par spectrométrie infrarouge
Reference number
ISO 19087:2018(E)
©
ISO 2018
---------------------- Page: 3 ----------------------
SIST ISO 19087:2019
ISO 19087:2018(E)
COPYRIGHT PROTECTED DOCUMENT
© ISO 2018
All rights reserved. Unless otherwise specified, or required in the context of its implementation, no part of this publication may
be reproduced or utilized otherwise in any form or by any means, electronic or mechanical, including photocopying, or posting
on the internet or an intranet, without prior written permission. Permission can be requested from either ISO at the address
below or ISO’s member body in the country of the requester.
ISO copyright office
CP 401 • Ch. de Blandonnet 8
CH-1214 Vernier, Geneva
Phone: +41 22 749 01 11
Fax: +41 22 749 09 47
Email: copyright@iso.org
Website: www.iso.org
Published in Switzerland
ii © ISO 2018 – All rights reserved
---------------------- Page: 4 ----------------------
SIST ISO 19087:2019
ISO 19087:2018(E)
Contents Page
Foreword .v
Introduction .vi
1 Scope . 1
2 Normative reference . 1
3 Terms and definitions . 1
4 Principle . 2
5 Apparatus, equipment and reagents . 3
6 Sampling . 7
6.1 Sample collection . 7
6.2 Transport . 8
7 Preparation . 9
7.1 Preparation of calibration samples . 9
7.1.1 Preparation of direct-on-filter calibration samples . . 9
7.1.2 Preparation of redeposition calibration samples .10
7.1.3 Preparation of KBr pellet calibration samples .10
7.2 Preparation of the collection substrate for indirect analysis .11
7.2.1 PVC, MCE and polycarbonate filters .11
7.2.2 Cellulose nitrate filters .12
7.2.3 Polyurethane foams . .12
7.3 Redeposition onto analysis filter .13
7.3.1 Crucibles from the furnace .13
7.3.2 Bottles or beakers from a plasma asher .13
7.4 Preparation of KBr pellets .14
8 Analytical procedure .14
8.1 Gravimetric analysis for respirable dust .14
8.2 Fourier-Transform Infrared analysis .15
8.2.1 Background correction .15
8.2.2 Measurement .15
8.3 Calibration .15
9 Evaluation of Fourier-Transform Infrared spectra .17
9.1 General aspects .17
9.2 RCS quantification using peak height .17
9.3 RCS quantification using peak integral .18
[12][14]
9.3.1 Determination of the absorption in the range of the analytical bands .18
[20]
9.3.2 Subtraction of a reference spectrum .18
9.3.3 Other evaluation methods .20
9.4 Interferences .20
10 Calculation of results .20
10.1 Concentration of RCS .20
11 Performance characteristics .21
11.1 Limit of detection .21
11.2 Limits of quantification .21
11.3 Uncertainty .21
11.4 Differences between samplers .21
12 Test report .22
Annex A (normative) Sample treatment strategies for the removal of interferences .23
Annex B (informative) Differences between samplers (cyclones and other types) .24
Annex C (informative) .26
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SIST ISO 19087:2019
ISO 19087:2018(E)
Annex D (normative) Examples of dust collection substrates and analysis filters .28
Bibliography .29
iv © ISO 2018 – All rights reserved
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SIST ISO 19087:2019
ISO 19087:2018(E)
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).
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. Details of
any patent rights identified during the development of the document will be in the Introduction and/or
on the ISO list of patent declarations received (see www .iso .org/patents).
Any trade name used in this document is information given for the convenience of users and does not
constitute an endorsement.
For an explanation on 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 the following
URL: www .iso .org/iso/foreword .html.
This document was prepared by Technical Committee ISO/TC 146, Air quality, Subcommittee SC 2,
Workplace air.
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Introduction
Respirable crystalline silica (RCS) is a hazard to the health of workers in many industries through
exposure by inhalation. Industrial hygienists and other public health professionals need to determine
the effectiveness of measures taken to control workers’ exposure. The collection of samples of air
during a work activity and then measuring the amount of respirable crystalline silica are often done to
assess an individual’s exposure, their respiratory protection, or the effectiveness of controls. Fourier-
Transform Infrared (FTIR) analysis of crystalline silica in a sample of respirable dust collected on a
collection substrate is employed in many countries to measure and estimate exposure to RCS. FTIR is
able to measure quartz and cristobalite.
This document specifies the analysis procedures for the measurement of RCS through three methods:
a) Direct-on-filter method: a method of analysing RCS directly on the air sample filter. A specific
requirement of this method is that the sampler used for the workplace measurements is the same
as that used for the preparation of calibration samples.
b) Indirect method by redeposition: a method whereby the dust is recovered from the collection
substrate and deposited onto a filter for analysis.
c) Indirect method by potassium bromide (KBr) pellet: a method whereby the dust is recovered from
the collection substrate and pressed into a potassium bromide (KBr) pellet for analysis.
Many different types of sampling apparatus are used to collect respirable dust, according to the
occupational hygiene convention. This document is designed to accommodate the variety of samplers
and collection substrates available to analysts. This document is used in conjunction with ISO 24095
which promotes best practice for these analyses.
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INTERNATIONAL STANDARD ISO 19087:2018(E)
Workplace air — Analysis of respirable crystalline silica by
Fourier-Transform Infrared spectroscopy
1 Scope
This document is a standard for the analysis by Fourier-Transform Infrared (FTIR) of respirable
crystalline silica (RCS) in samples of air collected on collection substrates (i.e. filters or foams). Three
analytical approaches are described for whom the dust from the sample collection substrate is
a) analysed directly on sampled filter,
b) recovered, treated and deposited onto another filter for analysis, or
c) recovered, treated and pressed into a potassium bromide (KBr) pellet for analysis.
This document provides information on the instrumental parameters, the sensitivity of different
sampling apparatus, the use of different filters and sample treatment to remove interference. In this
document the expression RCS includes the most common polymorphs quartz and cristobalite.
This document excludes the less common polymorphs of crystalline silica, such as tridymite.
Under certain circumstances (i.e. low filter dust loads, low silica content), the analytical approach
described in this method cannot fulfil the expanded uncertainty requirements of ISO 20581. Guidance
for calculation of uncertainty for measurements of RCS is given in ISO 24095.
2 Normative reference
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 7708, Air quality — Particle size fraction definitions for health-related sampling
ISO 13137, Workplace atmospheres — Pumps for personal sampling of chemical and biological agents —
Requirements and test methods
EN 13205, Workplace exposure — Assessment ofsampler performance for measurement of airborne
particle concentrations
ISO 15767, Workplace atmospheres — Controlling and characterizing uncertainty in weighing collected
aerosols
ISO 18158, Workplace air — Terminology
ISO 24095, Workplace air — Guidance for the measurement of respirable crystalline silica
3 Terms and definitions
For the purposes of this document, the terms and definitions given in ISO 18158 and the following apply.
ISO and IEC maintain terminological databases for use in standardization at the following addresses:
— ISO Online browsing platform: available at https: //www .iso .org/obp
— IEC Electropedia: available at http: //www .electropedia .org/
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3.1 General definitions
3.1.1
respirable crystalline silica
RCS
inhaled particles of crystalline silica that penetrate into the unciliated airways according to the
respirable convention described in ISO 7708
3.2 Sampling definitions
3.2.1
analysis filter
suitable filter used to carry out the RCS analysis
Note 1 to entry: For direct-on-filter FTIR analysis the collection substrate is the analysis filter.
Note 2 to entry: For the indirect analysis the dust is removed from the collection substrate and redeposited onto
an analysis filter.
3.2.2
collection substrate
medium on which airborne chemical and/or biological agents are collected for subsequent analysis
Note 1 to entry: For the purpose of this document, filters, polyurethane foams and sampling cassettes are
examples of collection substrates for airborne particles.
4 Principle
This document provides three Fourier-Transform Infrared (FTIR) analytical approaches for the analysis
of RCS in respirable dust collected on a sample collection substrate.
a) Direct-on-filter method:
The respirable dust on the collection substrate (usually a 25 mm diameter filter) is measured
without transferring the dust to an analysis filter. The mass of RCS is determined from the FTIR
response, calibrated against filters loaded with known amounts of RCS reference material.
b) Indirect method (redeposition):
The dust from the sample collection substrate (i.e. a 37 mm diameter filter or a polyurethane
foam) is recovered, treated and deposited on another analysis filter (usually 25 mm diameter or
smaller) for analysis by the instrument. The instrument is calibrated by preparing test samples
from aliquots of a suspension of a reference material. The mass of RCS is determined from the FTIR
response, calibrated against analysis filters loaded with known amounts of RCS reference material.
c) Indirect method (KBr pellet):
The dust from the sample collection substrate (i.e. a 37 mm diameter filter or a polyurethane foam)
is recovered, treated and pressed into a KBr pellet for analysis by the instrument. The instrument
is calibrated by preparing KBr pellets with known amounts of a reference material. The mass of
RCS is determined from the FTIR response, calibrated against pellets loaded with known amounts
of RCS reference material.
Since the volume of air sampled is known, the concentration of RCS in the air is readily calculated.
Because the different aerosol samplers for respirable dust deposit the sample over the surface of the
filter in different ways, the FTIR instruments used for the direct-on-filter analysis approach shall be
calibrated for the aerosol sampler used to collect the samples.
The suitability of FTIR to determine the RCS concentration in a workplace sample depends on the
composition of the dust and potential interferences. If the FTIR method to subtract a reference
spectrum from the sample spectrum (refer to 9.3.2) does not lead to a satisfactory baseline profile, then
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the FTIR method is not suitable for the matrix and quantitative FTIR analysis cannot be carried out. As
an alternative XRD analytical method should be used. Qualitative X-ray diffraction (XRD) analysis can
be carried out prior to FTIR analysis to obtain information about the sample.
5 Apparatus, equipment and reagents
5.1 Sampling equipment
5.1.1 Samplers.
5.1.1.1 The particle size-selection performance of the samplers used shall match the criteria for
respirable dust as specified in ISO 7708 according to the test protocol in EN 13205-2.
5.1.1.2 Samplers using a filter or foam pad are suitable for this method.
NOTE Annex B provides information on the performance of different personal respirable samplers that are
currently in use.
NOTE Foam pads and silver membrane filters are not suitable for direct-on-filter method.
5.1.1.3 Cassettes holding filters shall be made of conductive material.
5.1.1.4 Each sampler should be labelled with a unique number, in order to identify samplers that start
to underperform after long-term use.
5.1.1.5 Samplers (sampling train) shall comply with the requirements for calibration in ISO 13137.
NOTE In some countries there can be exceptions due to national regulations.
5.1.2 Collection substrates and analysis filters.
5.1.2.1 Filters as collection substrates shall be of a diameter suitable for use in the selected sampler
and have a capture efficiency for respirable particles as specified in ISO 24095.
5.1.2.2 It is important for the analyst to know the composition of the collection substrate used to
collect the sample since it has a direct bearing on the analytical approach used. The collection substrates
generally used for the sampling of RCS, and their characteristics, are listed in Annex D.
NOTE Additional information about choice of filter material for quartz measurement in coal mine dust can
be found in Reference [24].
5.1.2.3 Filter materials listed in Annex D generally do not contain compounds that interfere with the
measurement of quartz and cristobalite. Impurities can be introduced during the filter manufacturing
process and background absorbance can increase depending on filter material. Therefore, batches of
filters should be regularly tested to detect potential interferences and background levels.
5.1.2.4 Variable background has an effect on the readability of absorbance spectra, increasing the
limit of detection for RCS. PVC and polypropylene used as analysis filters exhibit the least variability and
lowest background levels and thus are useful in situations where low limits of detection are required.
5.1.2.5 Weighing, if required, should be performed following ISO 15767 (see 8.1). Filters shall not be
[18]
weighed in cassettes as large weight variations have been reported . Reference shall be made to the
instructions of the collection substrate manufacturer.
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5.1.2.7 An important property for an analysis filter is that it is transparent to infrared and provides a
relatively low background variation near the absorbance for crystalline silica.
5.1.3 Sampling pumps.
Sampling pumps shall comply with the requirements of ISO 13137.
5.1.4 Flow meters.
Flow meters shall comply with the requirements of ISO 13137.
5.1.5 Other equipment required.
Other equipment required for sampling includes the following:
a) belts or harnesses to which the sampling pumps can conveniently be fixed;
b) flexible tubing, to connect the sampler to the sampling pump;
c) a means to transport the samples from the workplace to the laboratory, which minimises the
possibility of accidental transfers of collected dust to or from the collection substrate (filter or
foam). Transportation will usually require caps or covers for the samplers, filter cassettes or other
substrates, as detailed in the manufacturer’s instructions for use of the instruments;
d) a thermometer (readable to 1 °C) and a barometer (readable to 0,1 kPa), to measure atmospheric
temperature and pressure for flow rate correction, when the temperature and pressure at the time
of use differ from the conditions under which the flow meter was calibrated (ISO 24095).
5.2 Equipment for calibration
5.2.1 Dust cloud generator (needed for direct-on-filter analysis).
A device to generate atmospheres of reference material and contain them is needed when following
the direct-on-filter analytical approach. An example of such a device is given in Figure 1. This device is
constructed from borosilicate glass with a lid made from acrylic glass. An aerosol of dust is generated
into the upper cylindrical chamber by applying a short burst of pressurized air to a dust contained in a
bowl at the bottom. Sampling equipment shall be prepared following 6.1.1 to 6.1.6 and 6.1.9. Samplers
are fitted at the top of the device. To avoid agglomerations and charge interactions between the dust
and the filter inside the aerosol sampler it is recommended that the device be earthed (grounded).
NOTE An Aerosol generation device can also be useful for preparing samples for indirect FTIR methods.
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Dimensions in centimetre
Key
1 acrylic glass lid
2 holes for cyclone samplers
3 B29/32 cone and socket joint
4 bowl for sample
5 orifice diameter 1 mm
6 compressed air at approximately 50 psi
Figure 1 — Example of an aerosol generation apparatus
5.2.2 Laboratory equipment to prepare suspensions.
For the preparation of calibration samples, suspensions with a defined content of quartz dust can be
used. Volumetric flasks of 100 mL and 250 mL, a bath thermostat with a built-in cooling coil, working
temperature range shall include 20 °C, microlitre pipettes of variable volumes, with a range of between
50 µL and 1 000 µL, an Erlenmeyer flask and a magnetic stirrer.
5.3 Equipment for the determination of dust concentration
5.3.1 Balance.
Weighing should be performed according to ISO 15767. For the preparation of low masses of calibration
samples, a microbalance capable of weighing ±1 µg (or better) is required. An electrostatic eliminator
is needed when weighing collection substrates. For the weighing of foams from the CIP 10-R sampler
for example a balance with an analytical sensitivity of 10 µg with an operational range of 0 g to 20 g is
required.
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5.4 Equipment for sample preparation
5.4.1 Redeposition laboratory equipment.
Platinum or glazed ceramic crucibles, beakers, tongs, calibrated pipettes, ultrasonic bath, magnetic
stirrer, apparatus to filter a sample onto a 25-mm diameter filter, a pump to generate vacuum, and a
fume cupboard to contain dusts, vapours and gases.
5.4.2 KBr pellet laboratory equipment.
Platinum or glazed ceramic crucibles, tongs, a pump to generate vacuum, a boron carbide mortar and
pestle, a 50-mm agate or metal microspatula, a laboratory press for preparing KBr pellets, a KBr pellet
evacuable die (typically 13 mm), a pump to generate vacuum, a desiccator with silica gel desiccant, a
hair brush with anti-static effects (e.g. badger or camel hair) and glassine paper.
5.4.3 Equipment to recover dust from the collection substrate.
A furnace capable of operating at a minimum of 600 °C or a low temperature plasma asher to remove
the filter membrane. Tetrahydrofuran (THF) can be used for the dissolution of PVC filters instead of a
plasma asher or furnace.
NOTE To remove interfering substances temperatures of up to 1 000 °C may be required. To prevent
reactions occurring between silica and calcium carbonate at high temperatures, the latter may be removed by
washing with hydrochloric acid (5.6.2.3).
5.5 Equipment for analysis
5.5.1 Spectrometer.
−1 −1 −1
A FTIR spectrometer with a wavelength range from at least 4 000 cm to 400 cm and 4 cm
resolution or better. A suitable sample holder (e.g. a rotatable polarizer mount) is required so that the
sample can be rotated in its own plane. This will enable the effect of non-uniform sample deposition
to be reduced by taking absorbance measurements at several orientations. If the infrared beam in the
instrument has a circular cross-section, rotation is not required.
5.6 Reagents
5.6.1 Direct-on-filter reagents.
Reagents are not normally required for t
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