ISO/TS 11353:2026

Technical
Specification
ISO/TS 11353
First edition
Nanotechnologies — A test method
2026-01
for detection of nano-object(s)
release from mask media
Nanotechnologies — Une méthode d'essai pour la détection de la
libération de nano-objet(s) à partir de masques
Reference number
© ISO 2026
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Published in Switzerland
ii
Contents Page
Foreword .iv
Introduction .v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Abbreviation terms . 4
5 Classification . 4
6 Test requirements . 5
6.1 Qualification of nano-objects in the mask media .5
6.2 Test rig components .5
7 Test procedure . 7
7.1 Pre-conditioning .7
7.2 Air flow measurement .7
7.3 Sampling and monitoring of released nano-objects .7
7.3.1 Filter-based sampling methods .7
7.3.2 Real-time methods.8
8 Determination of qualitative properties of released nano-objects . 8
8.1 Measurands related to chemical measurement of nano-objects .8
8.1.1 General .8
8.1.2 TEM/SEM-energy dispersive X-ray spectroscopy (EDX) and wavelength-
dispersive X-ray spectroscopy (WDS) .9
8.1.3 Electron energy loss spectroscopy (EELS) .10
8.1.4 X-ray fluorescence spectroscopy (XRF) .10
8.1.5 Auger electron spectroscopy (AES) .10
8.1.6 Secondary ion mass spectroscopy (SIMS) .11
8.1.7 X-ray photoelectron spectroscopy (XPS) .11
8.2 Measurands related to size and shape measurement of nano-objects.11
8.2.1 General .11
8.2.2 Differential mobility analysing system (DMAS) . 12
8.2.3 Condensation particle counter (CPC) . 13
8.2.4 Transmission electron microscopy (TEM) combined with TEM grid samplers . 13
8.2.5 Scanning electron microscopy (SEM) . 13
8.2.6 Atomic force microscopy (AFM) .14
8.2.7 Single particle inductively coupled plasma–mass spectrometry (SP-ICP-MS) . 15
8.2.8 Field flow fractionation (FFF) .16
9 Reporting . 17
9.1 General information.17
9.2 Mandatory characteristics .17
Annex A (informative) Test report format for detection of nano-objects release from mask
media .18
Bibliography . 19

iii
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,
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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 document should be noted. This document was drafted in accordance with the editorial rules of the
ISO/IEC Directives, Part 2 (see www.iso.org/directives).
ISO draws attention to the possibility that the implementation of this document may involve the use of (a)
patent(s). ISO takes no position concerning the evidence, validity or applicability of any claimed patent
rights in respect thereof. As of the date of publication of this document, ISO had not received notice of (a)
patent(s) which may be required to implement this document. However, implementers are cautioned that
this may not represent the latest information, which may be obtained from the patent database available at
www.iso.org/patents. ISO shall not be held responsible for identifying any or all such patent rights.
Any trade name used in this document is information given for the convenience of users and does not
constitute an endorsement.
For an explanation of the voluntary nature of standards, the meaning of ISO specific terms and expressions
related to conformity assessment, as well as information about ISO's adherence to the World Trade
Organization (WTO) principles in the Technical Barriers to Trade (TBT), see www.iso.org/iso/foreword.html.
This document was prepared by Technical Committee ISO/TC 229, Nanotechnologies.
Any feedback or questions on this document should be directed to the user’s national standards body. A
complete listing of these bodies can be found at www.iso.org/members.html.

iv
Introduction
Increasing air pollution and the proliferation of airborne pathogens such as coronavirus are among the
most important threats to the global environment and human health. There are three main routes for
contaminants (aerosols, bio aerosols, gases and vapours) to enter the body, including respiratory system,
dermal and ingestion. Of these routes, the respiratory system is the most important and dominant way
[1]-[3]
of entry. Therefore, protection of the respiratory system is of particular importance, justifying the
use of mask media of a high level of protection. The emergence of the coronavirus pandemic and airborne
particulate matter (PM), pollution has led to remarkably high demand for face masks and, as a result, the
market for protective face masks has significantly increased. In this regard, polymeric fibrous media have
been developed. Fibrous media containing nano-objects, such as either nanofibers or nanoparticles or both,
have shown enhanced performance in trapping ultrafine particles, microbes and viruses, at lower pressure
drops compared to previous types (mask media without nano-objects. Nano-objects can be coated on the
surface of face mask fibres or nanofibres, or can also be embedded within the polymeric fibres or nanofibres
themselves. Two major production methods for face mask fibrous media, includes the melt blowing and
electrospinning processes. Both processes involve the production of fibres or nanofibres that can serve as a
matrix where nano-objects can be embedded or surface-applied. Despite the above-mentioned performance
advantages, face mask media containing nano-objects can potentially lead to unforeseen environmental
and human health hazards due to the possible release of nano-objects during their life cycle. Releases of
component nano-objects from face masks can occur as a result of their design, manufacture, misuse or
improper handling.
Nano-objects can be released into different media (such as air, sweat, effluent water) during product use
[4],[5]
and care. Generally, data on the fraction of nano-objects release from textile materials and products,
especially into the air, is limited. Research shows that the total amount of nanoparticles released from
investigated textiles ranges from less than 1 % to nearly 100 %, depending on the content of nanoparticles
contained within the textiles. In some textiles, the amount of nanoparticle release was lower than the
[6],[7]
detection limit of the implemented measuring equipment. The nature of the fabric is also one of the
other factors affecting the release of nanoparticles. Among the investigated textiles, those with synthetic
[6],[7]
fibres showed the highest release. Furthermore, the release behaviour of particles from a matrix
[8]
depends on how the particles are attached or embedded in it. Currently, no technical standard exists in
the public domain to detect the possible release of component nano-objects from face masks.
This document aims to fill this gap by specifying a test method for detection of nano-objects that can be
released from surgical masks, surgical respirators and barrier face coverings containing nanomaterial(s).
The release is only investigated by applying an air flow to the mask media, but not by contact to other
media, e.g. liquids or skin. In addition, this document also describes the sampling procedure and qualitative
characterization methods for released nano-objects. Moreover, the development of this document will
facilitate communication between user and manufacturer or producer and lead to the enhancement of the
related market.
v
Technical Specification ISO/TS 11353:2026(en)
Nanotechnologies — A test method for detection of nano-
object(s) release from mask media
1 Scope
This document specifies a test method for the detection of nano-objects release, irrespective of its causes,
from surgical masks, surgical respirator masks and barrier face coverings [reusable (regardless of washing
characteristics) and disposable types] containing nano-objects, irrespective of the type of production
technology.
In addition, this document also provides the sampling procedures and qualitative characterization methods
for released nano-objects. This document can be used to show the possible exposure due to release, which
relates to human health and safety.
2 Normative references
The following documents are referred to in the text in such a way that some or all of their content constitutes
requirements of this document. For dated references, only the edition cited applies. For undated references,
the latest edition of the referenced document (including any amendments) applies.
ISO 16890-2, Air filters for general ventilation — Part 2: Measurement of fractional efficiency and air flow
resistance
ISO 26824, Particle characterization of particulate systems — Vocabulary
ISO 27891, Aerosol particle number concentration — Calibration of condensation particle counters
ISO 15167, Petroleum products — Determination of particulate content of middle distillate fuels — Laboratory
filtration method
ISO 16976-1, Respiratory protective devices — Human factors — Part 1: Metabolic rates and respiratory flow
rates
ISO/TS 23302, Nanotechnologies — Requirements and recommendations for the identification of measurands
that characterise nano-objects and materials that contain them
ASTM F2100, Standard Specification for Performance of Materials Used in Medical Face Masks
EN 1822-4, High efficiency air filters (EPA, HEPA and ULPA) - Determining leakage of filter elements (scan
method)
3 Terms and definitions
For the purposes of this document, the terms and definitions given in ISO 16890-2, ISO 16976-1, ISO 26824,
ISO 27891, ASTM F2100, and EN 1822-4, and the following apply.
ISO and IEC maintain terminology databases for use in standardization at the following addresses:
— ISO Online browsing platform: available at https:// www .iso .org/ obp
— IEC Electropedia: available at https:// www .electropedia .org/

3.1
barrier face covering
’
product worn on the face specifically covering at least the wearer s nose and mouth with the primary
purpose to provide source control and a degree of particulate filtration to reduce the amount of inhaled
particulate matter
Note 1 to entry: The barrier face coverings are intended to be reusable or disposable.
Note 2 to entry: Reusable refers to the ability of a product to be used and laundered or cleaned multiple times and
maintain specific performance characteristic.
[SOURCE: ASTM F3502 -21: 2021, 3.1.3]
3.2
downstream
area or region into which fluid flows on leaving the test device
[SOURCE: ISO 29464:2024, 3.1.16, modified — "An air cleaner" changed to "the test device".]
3.3
face velocity
volumetric air flow rate divided by the filter face area
Note 1 to entry: Filter face velocity is expressed in m/s or cm/s.
[SOURCE: ISO 29464:2024, 3.1.20, modified — "Nominal air cleaner" replaced by "filter" and note to entry
replaced.]
3.4
mask media
materials used in the mask for capturing the contaminants
3.5
surgical mask
medical mask
product that covers the wearer's nose and mouth and provides a physical barrier to fluids and particulate
materials.
Note 1 to entry: These products are not classed as PRD.
[SOURCE: ISO/TS 16975-4:2022, 3.21]
3.6
surgical respirator
tight fitting respiratory protective device designed and tested for respiratory protection performance
for conformance to an applicable national standard e.g. rated as N95, FFP2, KN95 etc. as well as having
performance for fluid resistance and other parameters.
[SOURCE: ISO/TS 16975-4:2022, 3.22, modified — "compliance" changed to "conformance".]
3.7
nanomaterial
material with any external dimension in the nanoscale or having internal structure or surface structure in
the nanoscale
Note 1 to entry: The nano form of a material is a nanomaterial.
[SOURCE: ISO 80004-1:2023, 3.1.4, modified – Note 1 to entry deleted.]

3.8
nano-object
discrete piece of material with one, two or three external dimensions in the nanoscale
[SOURCE: ISO 80004-1:2023, 3.1.5]
3.9
nanofibre
nano-object with two external dimensions in the nanoscale and the third dimension significantly larger
Note 1 to entry: The largest external dimension is not necessarily in the nanoscale.
[SOURCE: ISO 80004-1:2023, 3.3.5]
3.10
nanoparticle
nano-object with all external dimensions in the nanoscale
Note 1 to entry: If the dimensions differ significantly (typically by more than 3 times), terms such as nanofibre or nano
plate are preferred to the term nanoparticle.
[SOURCE: ISO 80004-1:2023, 3.3.4]
3.11
particle size
linear dimension of a particle determined by a specified measurement method and under specified
measurement conditions
Note 1 to entry: Different methods of analysis are based on the measurement of different physical properties.
Independent of the particle property actually measured, the particle size is reported as a linear dimension, e.g. as the
equivalent spherical diameter.
[SOURCE: ISO 26824:2022, 1.5, modified — Symbols deleted and Notes 2 and 3 to entry deleted.]
3.12
particle size distribution
distribution of the quantity of particles as a function of particle size
Note 1 to entry: Particle size distribution may be expressed as cumulative distribution or a distribution density
(distribution of the fraction of material in a size class, divided by the width of that class).
Note 2 to entry: The quantity can be, for example, number, mass, or volume based.
Note 3 to entry: In this document, particle size distribution is discussed based on number.
[SOURCE: ISO/TS 80004-6:2021, 4.1.2, modified — Note 3 to entry added.]
3.13
particle shape
external geometric form of a particle
[SOURCE: ISO/TS 80004-6:2021, 4.1.3]
3.14
pressure drop
difference in absolute (static) pressure between two points in a system
Note 1 to entry: Resistance to air flow is measured in Pa.
[SOURCE: ISO 29464:2024, 3.1.43, modified — "An air flow system" changed to "a system" and "(inches of
water)" deleted from note to entry.]

3.15
upstream
region in a process system traversed by a flowing fluid before it enters that part of the test device
4 Abbreviation terms
AES Auger electron spectroscopy
AFM atomic force microscopy
CPC condensation particle counter
DEMC differential electrical mobility classifier
DMAS differential mobility analysing system
EDX dispersive X-ray spectroscopy
EELS electron energy loss spectroscopy
FIB focused ion beam
FFF field flow fractionation
HEPA high efficiency particulate air
ICP-MS inductive coupled plasma mass spectrometry
LB Langmuir-Blodgett
MCE mixed cellulose ester
NOAA nano-objects and their aggregates and agglomerates
PM particulate matter
PSD particle size distribution
SEM scanning electron microscope
SIMS secondary ion mass spectroscopy
SMPS scan mobility particle sizer
SP-ICP-MS single particle inductively coupled plasma–mass spectrometry
TEM transmission electron microscopy
ULPA unltra low particulate air
WDS wavelength-dispersive X-ray spectroscopy
XPS X-ray photoelectron spectroscopy
XRF X-ray fluorescence spectroscopy
5 Classification
Masks specified in this document are classified into three types: surgical masks, surgical respirator masks
and barrier face covering (both reusable and disposable types).

6 Test requirements
6.1 Qualification of nano-objects in the mask media
Manufacturers should report the physicochemical characteristics and composition of mask media, including
nano-objects, chemical and polymeric content, subject to agreement between relevant stakeholders. However,
in accordance with Tables 2 and 3, different techniques shall be used for size and shape characterization
[9]-[11]
such as SEM, AFM or TEM. The content and chemical composition of the nano-objects should also be
analysed using inductively coupled plasma mass spectrometry (ICP-MS] and SEM-EDX in accordance with
ISO/TS 23302 and ISO/TR 18196.
The characteristic measurements shall be reported in the typical report format shown in Annex A.
6.2 Test rig components
The proposed test rig scheme is shown in Figure 1. The concept of proposed test rig is adapted from SEMI
[13]
C-14 (x) for testing particle shedding or release from filters. To avoid any interferences due to the presence
of background particle concentrations, the test rig shall be equipped with a HEPA or ULPA filter located
between the blower and test rig. The temperature of the air at the test rig shall be 23 ± 5 °C and relative
[14]
humidity of 45 ± 10 %. The test rig shall be constructed from commercial components such as stainless
steel, and stainless steel sanitary fittings should be considered to allow easy mounting of the mask media
holder (outer Ø 114 mm, inner Ø 112,8 mm, corresponding to an effective area of 100 cm ) and facilitate
cleaning. Ideally, the equipment should be placed vertically at bench top level and supported.
The intake air for the rig is supplied by an appropriate blower and its flow rate is adjusted using a control
valve. While the control valve is shown schematically, in practice, a ball valve followed by a needle valve
may be used to control the flow. The test rig shall be designed such that the face velocities are 5 ± 0,5 cm/s,
10 cm/s, and 15 cm/s respectively (as shown in Table 1). The face velocity should not exceed 15 cm/s at
standard conditions. These represent the velocity of an adult human breathing for low, moderate and high
[15]-[18]
intensity physical activities.
An on/off valve is included to start or stop the airflow, while a control valve (a combination of a ball valve
and a needle valve) is used for precise flow adjustment.
[14]
The temperature of the air at the test device shall be 23 ± 5 °C and relative humidity of 45 ± 10 %.
The test rig includes sampling filters with porous support for mechanical strength and real-time measurement
instruments (such as a condensation particle counter or DMAS) both upstream and downstream to monitor
particle concentrations. A mass flow meter (measuring range of 10 and 100 l/min) is incorporated to ensure
accurate flow rate measurement. Finally, the exhaust air exits the system after passing through the test
section.
Table 1 — Face velocity values for different intensity physical activities
Type of intensity physical Peak expiratory flow rate Face velocity
activities (l/min)
(cm/s)
Low intensity 30 5
Moderate intensity 60 10
High intensity 85 15
Key
1 blower
2 HEPA or ULPA filter
3 on/off valve
4 control valve
5 sampling filter with the porous support (for mechanical strength of sampling filter)/real time measurements
(condensation particle counter or DMAS) in upstream
6 mask media holder with the diameter of: outer Ø 114 mm and inner Ø 112,8 mm (corresponding to an
effective area of mask media equal to 100 cm )
7 sampling filter with the porous support (for mechanical strength of sampling filter)/real time measurements
(condensation particle counter or DMAS) in downstream
8 mass flow meter measurement (measuring range of 10 and 100 l/min)
9 exhaust air
Figure 1 — Test rig for measuring released nano-objects

Key
A mask holder: outer Ø 114 mm and inner Ø 112,8 mm
B effective area of mask: 100 cm
C porous support pad
Figure 2 — Details about the mask media holder
7 Test procedure
7.1 Pre-conditioning
The specimen shall be pre-conditioned at 30 ± 5 % relative humidity and 21 ± 3 °C for a minimum of 4 h.
After pre-conditioning, the specimens should be tested within 5 min of being taken out of the conditioning
[15]
room.
The temperature measurement device shall be accurate to within ±1 °C. The relative humidity measurement
device shall be accurate to within ±2 %. Both temperature and relative humidity measurement devices shall
[14]
be calibrated annually.
7.2 Air flow measurement
The air flow rate is given for standardised conditions of the mass flow meter. The air flow rate should be
[15]-[18]
measured in accordance with ASTM F3502, ASTM F2100 and FDA guidance document (SM 501). .
Flow measurement shall be made by standardized flow measuring devices in accordance with ISO 15167.
7.3 Sampling and monitoring of released nano-objects
7.3.1 Filter-based sampling methods
The sampling filter is a Ø 37 mm membrane filter with the porous support (for the mechanical strength)
that is inserted into the sampling holder (open faced type). Polycarbonate (PC) filters (size: 25 mm and
pore size 0,2 μm), and Mixed ester (MCE) filters (size: 37 mm and pore size 0,45 μm) are used to collect the
[19]-[22]
released nanofibres and nano-objects respectively. The proposed sampling flow rate is approximately
7 ± 0,7 L/min, depending on the pressure drop due to different mask media, and the appropriate analytical
[20]-[22]
method. The sampling duration depends on the detection limit of the analyser. Samples shall be taken
both upstream (as a blank sample) and downstream of the mask media being tested. In accordance with
ISO/TS 23302, physicochemical characterization including size and particle size distribution (PSD), shape
and chemical properties of the samples shall be monitored in appropriate interval to detect the released
nano-objects. See ISO/TR 18196 for further information.

7.3.2 Real-time methods
In order to assess the likelihood of particle and fibre release from the investigated media, direct reading
methods can be utilized, which involves measuring the quantity (number), size, and size distribution. To
accomplish this, the aforementioned characteristics regarding the upstream and downstream measurement
media shall be determined, disregarding the chemical composition of the media.
NOTE Among the methods specified in Clause 8, only two methods are real time sampling method including
condensation particle counter (CPC) and differential mobility analysing system (DMAS).
8 Determination of qualitative properties of released nano-objects
8.1 Measurands related to chemical measurement of nano-objects
8.1.1 General
As different types of nano-objects including organic and inorganic compounds of different composition are
used for face mask media, a set of characterization techniques are listed here. It is recommended that the
characterization technique for each parameter be selected based on the type and expected composition of
the nano-object under study. A single technique alone often cannot provide sufficient information about all
parameters of interest for a particular nano-object under study, nor is one technique likely to fully capture
relevant information for a single parameter. Therefore, when available, it is recommended that more than
one technique should be used for any parameter investigation.
ISO/TS 23302 and ISO/TR 18196 provide guidance for selecting suitable chemical measurands based on the
claimed nano-objects.
Table 2 specifies requirements for methods, which are further detailed in the subsequent sub-clauses.

Table 2 — Released nano-objects chemical characteristic and measurement methods(s)
Characteristics Measurement Depth resolution of Lateral resolution of Limitation
method(s) the method the method
Composition TEM/SEM-EDX and 0,3 µm to 5 µm 0,5 µm For EDX using SEM,
WDS the specimens shall
be conductive. The
composition is rela-
tive.
Chemical bonding EELS with TEM 10 nm 0,1 nm Thin specimens, typ-
ically < 30 nm. Inten-
sity weak for energy
losses > 300 eV. Can
only be undertaken
with a TEM.
Elemental analysis XRF 5 µm to 20 µm 1 nm to 100 µm Normal quantita-
tive limit: 10 ppm
to 20 ppm (parts
per million). With
synchrotron radia-
tion source, absolute
detection limits:
100 ppb (parts per
billion).
Chemical identifica- AES 2 nm to 20 nm 10 nm Samples analysed
tion under high vacuum;
care shall be used for
non-conducting sam-
ples. Sensitivity (0,3
at. %). Matrix effects
in quantitative AES of
multicomponent sam-
ples to be considered
Elemental, isotopic, or SIMS ~ 1 nm (inorganic) 200 nm Quantification chal-
molecular composi- lenging. Samples ana-
~ 10 nm (organic)
tion of the surface lysed under vacuum.
Surface composition, XPS >1 nm >10 µm Samples normally an-
chemistry of coating, alysed under vacuum.
surface functionali- Sensitivity (0,1 at. %).
zation
8.1.2 TEM/SEM-energy dispersive X-ray spectroscopy (EDX) and wavelength-dispersive X-ray
spectroscopy (WDS)
X-ray spectrometry is a technique that uses an electron beam and the surface of the sample to produce
individual photons. EDX and WDS analysis is a powerful method that is often is attached to SEMs and
TEMs. It works by bombarding a sample with electrons, generating characteristics X-rays that identify what
elements are present, and in what proportion. The X rays are produced from an interaction volume below
the point where the electron beam irradiates the sample. One electron is removed to create a vacancy into
which another can “fall” from an outer orbit. The X-rays result from transitions between inner orbitals,
which are normally full. This is then used to build up a histogram representing the distribution of X-ray
emission energies. To used EDX, calibration with known standards is required at each specific accelerating
[9],[12]
voltage used (typically 10 keV to 20 keV). A suitable sample holder or stub for mounting the samples
should be selected for analysis. Apply a small amount of conductive adhesive or carbon tape on the sample
holder or stub. Carefully place the nanoparticles or nanofibres onto the adhesive or tape, ensuring proper
spacing between individual nanoparticles or nanofibres. Gently press the samples onto the adhesive or tape
to ensure good contact. Apply a thin, conductive coating (e.g., gold or carbon) onto the samples to improve
[23],[24]
surface conductivity and minimize charging effects during the SEM analysis.

8.1.3 Electron energy loss spectroscopy (EELS)
EELS, is an analytical method based on the interaction of a material with a beam of electrons where some of
the electrons undergo inelastic scattering by fast electrons while they undergo inelastic interactions with
the sample, often exhibiting features due to specific inelastic loss processes. EELS analyses the binding
energy state of an element by measuring the energy lost when an incident electron beam excites electrons
in the sample. When coupled with a TEM, it is considered complementary to EDX. Compared to EDX, EELS
provides improved signal to noise ratio, better spatial resolution (down to 1 nm), higher energy resolution
[9],[12],[25]
(<1 eV for EELS) and increased sensitivity to the lower atomic number elements.
This technique is used to determine the chemical information on the structure of solids and the oxidation
state of the elements, including the atomic structure and chemical properties of a specimen. EELS can
measure the type and quantity of atoms present, as well as the chemical state of atoms and the collective
[9],[12],[25]
interactions of atoms with their neighbours.
For analysis, the sample must be securely mounted onto a suitable substrate or holder. Common choices
include grids, thin films, or specialized sample holders designed for EELS analysis. The choice of holder
depends on the nature of the sample and the requirements of the EELS instrument. The substrate and sample
surface must be completely clean in order to remove any contaminants or impurities that can possibly
interfere with the EELS analysis. Common cleaning methods include ultrasonic cleaning, solvent rinsing, or
[26]
plasma cleaning.
8.1.4 X-ray fluorescence spectroscopy (XRF)
XRF is a non-destructive and fast analytical technique used to determine the elemental chemical analysis
of all kinds of materials. X-rays produced by a source irradiate the sample, and the element present in the
sample will emit fluorescent X-ray radiation with discrete energies that are characteristic for these elements.
By measuring the energies and the intensities of the emitted energies, it is possible to determine which
element (qualitative analysis) and how much of each element (quantitative analysis) is present in the sample.
[9],[12],[27],[28]
It can be used for nano-objects and materials that contain them for chemical identification.
For analysis, the samples are typically deposited onto a flat, homogeneous substrate such as a polycarbonate
filter, glass slide, or silicon wafer, chosen for minimal background interference. To achieve uniformity, the
sample may be dispersed in a solvent and then drop-cast, spin-coated, or filtered onto the substrate. Once
prepared, the sample is dried thoroughly to eliminate moisture or solvents that can affect the measurement.
For optimal results, the sample should cover the analysis area uniformly and remain free from contamination.
8.1.5 Auger electron spectroscopy (AES)
AES provides quantitative elemental and chemical state information from the surfaces of solid materials
and works in ultra-high vacuum. This technique uses the Auger effect, which is a non-radiative decay of an
electron impact created core hole, leading to the emission of energetic Auger electrons. Excitation of the
sample with an energetic electron beam results in the generation of a core hole. Relaxation from this excited
state occurs when this core hole is filled by an electron from a higher energy state with the simultaneous
emission of either an X-ray photon or an Auger electron. An electron energy analyser is used to measure the
energy of the emitted Auger electrons. From the kinetic energy and intensity of an Auger peak, the elemental
identity and quantity of a detected element can be determined. In some cases, chemical state information is
[9],[12],[29],[30]
also available from the measured peak position and observed peak shape. Due to the relatively
low energies (<3 keV) of the emitted Auger electrons, its mean free path within the sample is limited to less
[12]
than 10 nm, making AES inherently surface sensitive.
In order to prepare the sample for analysis, the sample must be securely mounted on a suitable substrate,
typically a clean and flat surface. Common choices include metal foils, silicon wafers, or specialized
sample holders designed for AES. The substrate and sample surface must be completely clean to remove
any contaminants or impurities that can possibly affect the AES measurements. AES analysis is typically
performed under high vacuum conditions to avoid interference from air or other gases. Carefully transfer the
prepared sample into the vacuum chamber of the AES instrument using appropriate handling techniques,
[31]
such as a load lock or glovebox.

8.1.6 Secondary ion mass spectroscopy (SIMS)
SIMS is a surface chemical analysis technique used for solid materials. A sample surface is bombarded by
a primary beam of heavy particles, and the secondary ions that are sputtered from the sample surface are
collected using a spectrometer. The secondary ions (the mass/charge ratios) provide information on the
composition, such as the elemental, molecular, and isotopic composition of a material’s surface. SIMS is a
highly sensitive technique for characteristic feature of the surface chemistry (top 1 nm) of specimens, which
[9],[12],[32],[33]
in this case would be ensembles of nano-objects.
In order to prepare the sample for analysis, it shall be mounted on a suitable substrate. Commonly used
substrates include silicon wafers or metal grids. The choice of substrate depends on the nature of the sample
and the requirements of the SIMS instrument. Clean the substrate and the sample surface to remove any
contaminants or residues that can interfere with the SIMS analysis. Common cleaning methods include
[34]
sonication in solvents, plasma cleaning, or use of cleaning agents like piranha solution.
If the nanoparticles or nanofibres are not strongly adhered to the substrate, it can be necessary to apply a
fixative to ensure their immobilization. Various fixatives can be used depending on the sample properties,
such as adhesives or surface coatings. For samples with rough surfaces or protruding features, it can be
necessary to smooth the surface to achieve better SIMS analysis results. Techniques like mechanical
[34]
polishing, ion milling, or FIB milling can be employed for surface preparation.
8.1.7 X-ray photoelectron spectroscopy (XPS)
XPS is the most widely used surface analysis technique because it can be applied to a broad range of materials
and provides valuable quantitative and surface chemistry information. In XPS, a sample is irradiated with
X-rays, which excite a photoelectron from a core level of the atoms, and it is emitted with a kinetic energy
equal to that of the incident photon minus its binding energy. An electron energy analyser is used to measure
the energy of the emitted photoelectrons. From the binding energy and intensity of the photoelectron peak,
[9],[12],[35]
the elemental identity, chemical state, and quantity of a detected element can be determined.
In the majority of XPS applications, sample preparation and mounting are not critical. Typically, the sample
is mechanically attached to the specimen mount, and analysis is begun with the sample in the as-received
condition. Additional sample preparation is discouraged in many cases because any preparation can modify
[35]
the surface composition.
8.2 Measurands related to size and shape measurement of nano-objects
8.2.1 General
The physical characteristics that shall be determined include the shape, and size and PSD of nano-objects.
PSD refers to a set of numerical values that express the relative or, in rare cases, the absolute number of
particles in different size classes or bins ranging from the smallest to the largest particle size.
Shape refers to the external geometric form of a particle. When direct observational techniques such as
microscopy are used, more specific measures can be defined in image analysis software to describe the
shape of an object. Commonly used measures include:
— Feret elongation, which is the ratio between the maximum Feret diameter and minimum Feret diameter,
where Feret diameter is calculated by measuring the distance between two parallel tangential lines in a
specific direction;
— aspect ratio, which is the proportional relationship between the length of a particle and its width;
— convexity, which is the ratio between the projected area of the object and the area of its convex hull.
The appropriate size and shape measurands based on the claimed nanomaterials should be selected in
accordance with ISO/TS 23302 and ISO/TR 18196 guidance.
Table 3 summarizes the list of characteristics and measurement methods that should be carried out to
detect the physical properties of the released nano-objects.

Table 3 — Released nano-objects physical characteristics and measurement method(s)
Characteristics Measurement method(s) Size range Limitation
Number-electrical mobility DMAS/CPC 3 nm to 1 000 nm Measuring takes at least
size distribution one minute; not adapted for
fast phenomena.
Size and size distribution FESEM/SEM/TEM 1 nm to 1 mm Needs sample preparation
onto a substrate. Slow,
individual particle meas-
urement.
SEM/TEM is not a real time
technique. Typical sampling
efficiency has a minimum
(10 %) at 20 nm to 30 nm.
Shape FESEM/SEM/TEM, AFM 1 nm to 1 000 nm Typical sampling efficiency
has a minimum (10 %) at
20 nm to 30 nm.
Requires sample prepa-
ration onto a substrate.
Particle analysis can be
automated using image
analysis software. SEM/
TEM are not real time tech-
niques. In AFM, use z height
of particles as resolution
limited by probe size in x
and y directions.
Number-weighted particle sp-ICP-MS 10 nm to 2 µm Requires proper dilution
size distribution (not directly applicable to
high number concentra-
tion). Requires known den-
sity and shape of particles.
Size FFF 1 nm to ~50 µm Requires method develop-
ment and validation.
Long analysis times for
highly polydisperse samples
(>1 h).
Sample required to be dis-
persed in liquid.
8.2.2 Differential mobility analysing system (DMAS)
DMAS, also known as scanning mobility particle sizer (SMPS), as a real-time technique are composed of a
differential electrical mobility classifier (DEMC),
...