ISO/TR 20489:2018

Nanotechnologies — Sample preparation for the characterization of metal and metal-oxide nano-objects in water samples

This document provides an overview of approaches of sample preparation (i.e. pre-treatment and size-fractionation) for analytical measurements applied to surface and drinking water, potentially containing relevant amounts and types of metal and metal oxide nano-objects, including collection from source and storage of samples, pre-concentration of analytes, and their fractionation.

Nanotechnologies — Préparation des échantillons pour la caractérisation de nano-objets métalliques et d'oxydes métalliques dans les échantillons d'eau

General Information

• Status: Published
• Publication Date: 11-Dec-2018
• ICS: 07.120 - Nanotechnologies
• Technical Committee: ISO/TC 229 - Nanotechnologies
• Drafting Committee: ISO/TC 229 - Nanotechnologies
• Current Stage: 6060 - International Standard published
• Due Date: 27-Mar-2019
• Completion Date: 12-Dec-2018

Standards Content (Sample)

TECHNICAL ISO/TR
REPORT 20489
First edition
2018-12
Nanotechnologies — Sample
preparation for the characterization
of metal and metal-oxide nano-objects
in water samples
Nanotechnologies — Préparation des échantillons pour la
caractérisation de nano-objets métalliques et d'oxydes métalliques
dans les échantillons d'eau
Reference number
ISO/TR 20489:2018(E)
©
ISO 2018

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ISO/TR 20489:2018(E)

COPYRIGHT PROTECTED DOCUMENT
© ISO 2018
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ii © ISO 2018 – All rights reserved

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ISO/TR 20489:2018(E)

Contents Page
Foreword .iv
Introduction .v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Symbols and abbreviated terms . 2
5 Types of metal and metal oxide-based manufactured nano-objects .2
6 Types of water matrices of interest . 2
7 Sample collection and storage. 3
7.1 General . 3
7.2 Containers for sample collection and storage . 3
8 Sample pre-treatment . 3
8.1 Introduction . 3
8.2 Sedimentation and centrifugation . 4
8.2.1 Sedimentation . 4
8.2.2 Centrifugation . 4
8.2.3 Stepwise sedimentation and centrifugation . 4
8.2.4 Factors affecting centrifugation and sedimentation . 4
8.2.5 Advantages and limitations of centrifugation. 5
8.3 Filtration . 5
9 Size fractionation techniques . 5
9.1 Introduction . 5
9.2 Field-flow fractionation (FFF) . 6
9.2.1 Introduction . 6
9.2.2 Advantages and limitations . 6
9.3 Ultrafiltration . 7
9.4 Size exclusion chromatography . 7
Annex A (informative) Relevant nano-object characterization techniques .8
Bibliography . 9
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ISO/TR 20489:2018(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 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.
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ISO/TR 20489:2018(E)

Introduction
With the increasing use of manufactured nano-objects in commercial products and applications, such
as consumer and healthcare products, solar panels, batteries, surface coatings, and water treatment, it
is likely that these nano-objects will eventually be released to the environment, especially in aquatic
environments. There are, however, limited technical data available on the occurrence/transport/fate
of manufactured nano-objects after they are released to the aquatic environment. Together with the
current global shortage of water supply and an increasing demand for water recycling, concerns for the
potential health impacts of manufactured nano-objects in water will increase.
Related to nano-objects in aqueous matrices, knowledge of environmental parameters like natural
organic matter content, pH, ionic strength (IS) etc., is important since these may influence particle
size, fate, stability and chemical composition. An aqueous sample can be a complex mixture of particles
of different nature, size, reactivity, composition, agglomeration state and shape. Hence the initial
preparation of the samples, such as pre-treatment and size fractionation, are critical steps for any
subsequent analysis of the nano-objects. A consolidated table listing common fractionation techniques
[1] [2]
is given by Simonet, et al. and Hassellov, et al. .
Although several methods for the detection and characterization of manufactured nano-objects in
aqueous matrices are described in ISO/TR 18196:2016, the methods are at various stages of development
into technical specifications or standards. Most importantly, there is no accepted standard as yet on
pre-analysis treatment (i.e. collection, storage and size fractionation) of manufactured nano-objects
in water. This document can contribute to the development of a future international standard for the
analysis and characterization of metal and metal-oxide nanoparticles in aqueous matrices. This will
allow interlaboratory comparison of results and contribute to future studies of commercial products
containing manufactured nano-objects, thus, finally, support the growth of nanotechnology related
industries.
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TECHNICAL REPORT ISO/TR 20489:2018(E)
Nanotechnologies — Sample preparation for the
characterization of metal and metal-oxide nano-objects in
water samples
1 Scope
This document provides an overview of approaches of sample preparation (i.e. pre-treatment and
size-fractionation) for analytical measurements applied to surface and drinking water, potentially
containing relevant amounts and types of metal and metal oxide nano-objects, including collection
from source and storage of samples, pre-concentration of analytes, and their fractionation.
2 Normative references
There are no normative references in this document.
3 Terms and definitions
For the purposes of this document, the following terms and definitions 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/
3.1
manufactured nanomaterial
nanomaterial intentionally produced to have selected properties or composition
[SOURCE: ISO/TS 80004-1:2015, 2.9]
3.2
measurand
quantity intended to be measured
[SOURCE: ISO/IEC Guide 99:2007, 2.3, modified — The notes to entry have been deleted.]
3.3
nano-object
discrete piece of material with one, two or three external dimensions in the nanoscale
Note 1 to entry: The second and third external dimensions are orthogonal to the first dimension and to each other.
[SOURCE: ISO/TS 80004-2: 2015, 2.2]
3.4
nanostructured material
material having internal nanostructure or surface nanostructure
Note 1 to entry: If external dimensions are in the nanoscale, the term nano-object (3.2) is recommended.
[SOURCE: ISO/TS 80004-1:2015, 2.7, modified — Note 1 to entry has been replaced.]
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ISO/TR 20489:2018(E)

3.5
surface water
water which flows over, or rests on, the surface of a land mass
[SOURCE: ISO 13164-1:2013, 3.1.20]
3.6
drinking water
water either in its original state or after treatment, intended for drinking, cooking, food preparation, or
other domestic purposes, regardless of its origin
Note 1 to entry: Also known as potable water.
[SOURCE: ISO 5667-5:2006, 2.2, modified]
4 Symbols and abbreviated terms
HDPE high density polyethylene
FFF field-flow fractionation
Flow FFF flow field-flow fractionation
UF ultrafiltration
SEC size exclusion chromatography
GPC gel permeation chromatography
SDS sodium dodecyl sulfate
DLS dynamic light scattering
UV-vis ultraviolet–visible spectroscopy
RC regenerated cellulose
PES polyethersulfone
5 Types of metal and metal oxide-based manufactured nano-objects
1)
Based on the relevance of existing commercial products , the following metal and metal oxide-based
nano-objects were considered in the development of this document:
— Titanium dioxide (TiO ): One of the most commonly used nanomaterial ingredients in many common
2
consumer products (e.g. sunscreens, antifungal paints) and medical products;
— Zinc oxide (ZnO): Also widely used in sunscreens and medical products;
— Silver (Ag): Commonly used as an antibacterial agent in consumer textiles and medical products;
— Gold (Au): Widely used in biomedical applications, including bioassays, drug delivery and
hyperthermal therapy.
6 Types of water matrices of interest
Two types of water matrices were considered in this document, surface water and drinking water.
Surface water is the primary water source receiving waste streams, and thus it is prone to receive
1) Industry-wide applications: http: //www .understandingnano .com/nanoparticles .html.
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ISO/TR 20489:2018(E)

manufactured nano-objects used in various commerical products. Drinking water in urban cities
is produced by water treatment plants to remove all particulates which can include nano-objects.
However, Kaegi and coworkers have found trace quantities of nano-objects in water samples after
[13]
treatment . Thus, with increasing use of manufactered nano-objects in commercial products, it is
likely that monitoring of nano-objects in drinking water will become important in the future.
7 Sample collection and storage
7.1 General
To minimize changes in the state of water samples from the point of sample collection to analysis,
precaution should be taken during collection, transport and storage. Currently there is no standard in
collection, transport and storage of surface water samples containing nano-objects, but the following
ISO publications on water quality – Sampling, should be used as a starting point for the development of
nano-object specific procedures:
— ISO 5667-1 on guidance on the design of sampling programmes and sampling techniques;
— ISO 5667-3 on preservation and handling of water samples as well as the use of sample containers;
— ISO 5667-4 on guidance on sampling from lakes;
— ISO 5667-5 on guidance on sampling of drinking water from treatment works and piped distribution
systems;
— ISO 5667-6 on guidance on sampling of rivers and streams.
Since nano-objects in surface water may undergo continuous physicochemical changes, it is useful to
carry out the analysis of the samples with minimal delay.
7.2 Containers for sample collection and storage
Besides taking guidance from ISO 5667-3, common types of containers used in collection and storage
[8][9][10]
of freshwater samples for nano-object analysis include high density polyethylene (HDPE) and
[11]
borosilicate glass . The containers, especially HDPE, are typically pre-washed with dilute acid before
use. For physicochemical analysis of nano-objects, the collected samples are typically stored at ambient
or sub-ambient temperatures but without freezing. Very often, water samples require stabilization and
addition of anti-microbial agents to allow storage.
8 Sample pre-treatment
8.1 Introduction
Raw water samples collected from an industrial or environmental source often require pre-treatment
to (i) remove large particulates and/or (ii) concentrate the nano-objects of interest. Together with
dilution techniques (not discussed here), these are the main pre-treatment methods before the sample
can be used for further size fractionation and/or analysis.
WARNING — Since nano-objects can adsorb onto large particulates, the following pre-treatment
methods may potentially remove nano-objects to some extent.
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8.2 Sedimentation and centrifugation
8.2.1 Sedimentation
In sample pre-treatment, sedimentation can be used to reduce large particulates from the raw water
samples, leaving the nano-objects in the water suspension so that the subsequent sample treatment /
analysis can function effectively.
Gravitational sedimentation is a process to allow large and/or dense particles to settle out of the
water column due to earth gravity. It is a simple process and suitable for processing from small to
large quantities of samples (e.g. 1 ml to 20 l). The process usually takes a few hours to complete and
[12]
particles > 5 μm in diameter can readily be removed from the water sample . The advantage of
gravitational sedimentation is simplicity without the need for use of expensive instrumentation. It may
be used as an initial treatment step, to remove the largest (massive) materials quickly and conveniently,
not intended to remove sub-micrometre particles.
8.2.2 Centrifugation
Besides sedimentation, centrifugation is another way to remove large particulates from the raw water
samples. In addition, centrifugation is capable of concentrating nano-objects in the case where the
number of nano-objects in the water sample is too low for the downstream analysis.
Centrifugation is a process that uses the centrifugal force to differentially separate constituents in
heterogeneous mixtures according to their effective mass (density and size), as the denser or larger
constituents of the mixture migrate away from the axis of the centrifuge more rapidly and form a
sediment. The sedimentation rate is specified by the angular velocity usually expressed as revolutions
per minute (RPM), or acceleration expressed as gravitational force (g-force). The conversion factor
between RPM and g depends on the radius of the centrifuge rotor. A particle’s settling velocity in
centrifugation is a function of size and shape of the particles, centrifugal acceleration, the volume
fraction of solids present, the density difference between the particle and the liquid medium, and the
viscosity of the liquid. The sedimentation rate is zero when the density of the particle and liquid are the
same (i.e. no density contrast exists).
8.2.3 Stepwise sedimentation and centrifugation
Kaegi and coworkers developed this technique for water samples containing different sizes of nano-
[13]
objects . First, the water sample (surface or drinking water) was allowed to stand for 2 h to remove
large particles. The top layer (top 2 cm, equivalent to 1 l or 15 % v/v) of the water sample was then
extracted and centrifuged at 330 g for 30 min to sediment micrometre particles. The top layer (top 2 cm
or 15 % v/v) of the centrifuged sample was extracted and subjected to a second centrifugation at 2 700 g
for 1 h to sediment particles >200 nm in diameter. The supernatant after the second centrifugation
should be highly enhanced in nano-objects, which can be further concentrated via higher speed
centrifugation.
8.2.4 Factors affecting centrifugation and sedimentation
8.2.4.1 Sedimentation rate
Metal-based nano-objects separated by centrifugation can be obtained either in a supernatant or as a
sediment. Collecting nano-objects as sediment is more often practiced since it may separate the nano-
objects of interest from the dissolved constituents in the water sample. In general, the smaller nano-
objects require larger acceleration (larger g-force) or faster rotation and longer centrifugation time.
For example, centrifugation at 7 000 g to 10 000 g for 20 min to 30 min has been employed successfully
for sedimentation of gold nano-objects 15 to 20 nm in diameter, while 15 000 g to 18 000 g for 30 min
[14][15]
has been employed for gold nano-objects 5 to 10 nm in diameter . Collecting nano-objects in the
supernata
...