SIST EN ISO 2613-1:2023
(Main)Analysis of natural gas - Silicon content of biomethane - Part 1: Determination of total silicon by atomic emission spectroscopy (AES) (ISO 2613-1:2023)
Analysis of natural gas - Silicon content of biomethane - Part 1: Determination of total silicon by atomic emission spectroscopy (AES) (ISO 2613-1:2023)
This document is applicable to the measurement of the total silicon content in gaseous matrices such as biomethane and biogas. Silicon is present in a gas phase contained predominantly in siloxane compounds, trimethylsilane and trimethylsilanol. The analytical form of the silicon measured in liquid phase after conducted sampling and derivatization procedure is soluble hexafluorosilicate anion stable in slightly acidified media. Total silicon is expressed as a mass of silicon in the volume of the analysed gas.
This document is applicable to stated gaseous matrices with silicon concentrations up to 5 mg/m3, and it is prevalently intended for the biomethane matrices with Si mass concentration of 0,1 mg/m3 to 0,5 mg/m3.
With adaptation to ensure appropriate absorption efficiency, it can be used for higher concentrations. The detection limit of the method is estimated as 0,05 mg/m3 based on a gas sample volume of 0,020 m3. All compounds present in the gas phase are volatile at the absorption and derivatization temperature and gaseous organosilicon species are trapped in absorbance media and derivatized into analytical silicon that is measured by this method. The concentration of the silicon is measured in diluted derivatization media using atomic emission spectrometry upon atomisation/ionisation in microwave or inductively coupled plasma.
Unless specified otherwise, all volumes and concentrations refer to standard reference conditions (temperature, 273 K, and pressure, 101,325 kPa).
NOTE When using appropriate dilution factors, the method can also be applied for silicon concentrations above 5 mg/m3.
Analyse von Erdgas - Siliziumgehalt von Biomethan - Teil 1: Bestimmung des Gesamtsiliziumgehalts durch AES (ISO 2613-1:2023)
Dieses Dokument ist für die Messung des Gesamt Siliziumgehalts in gasförmigen Matrices wie Biomethan und Biogas anwendbar. Silizium liegt in einer Gasphase vor, die vorwiegend in Siloxanverbindungen, Trimethylsilan und Trimethylsilanol enthalten ist. Die analytische Form des in der Flüssigphase gemessenen Siliziums nach Durchführung des Probenahme und Derivatisierungsverfahrens sind lösliche Hexafluorsilicat Anionen, die in leicht angesäuerten Medien stabil sind. Der Gesamt Siliziumgehalt wird als Masse des im analysierten Gasvolumen vorhandenen Siliziums angegeben.
Dieses Dokument ist für festgelegte gasförmige Matrices mit Siliziumkonzentrationen bis 5 mg/m3 anwendbar, und ist vorwiegend für die Biomethan Matrices mit einer Si-Massenkonzentration von 0,1 mg/m3 bis 0,5 mg/m3 Si vorgesehen.
Mit einer Anpassung zur Sicherstellung eines angemessenen Absorptionsgrades kann es auch für höhere Konzentrationen angewendet werden. Die Nachweisgrenze des Verfahrens wird auf 0,05 mg/m3 abgeschätzt, basierend auf einem Gasprobenvolumen von 0,020 m3. Alle Verbindungen, die in der Gasphase vorliegen, sind bei der Absorptions und Derivatisierungstemperatur flüchtig, und gasförmige Siloxane werden in Absorptionsmedien eingefangen und in eine analytische Form von Silizium derivatisiert, welche mit diesem Verfahren gemessen wird. Die Siliziumkonzentration wird in verdünnten Derivatisierungsmitteln mittels Atomemissionsspektrometrie mit Atomisierung/Ionisation in Mikrowellen oder induktiv gekoppeltem Plasma gemessen.
Sofern nicht angegeben, beziehen sich alle Volumina und Konzentrationen auf Normbedingungen (Temperatur, 273 K, und Druck, 101,325 kPa).
ANMERKUNG Bei Anwendung geeigneter Verdünnungsfaktoren kann das Verfahren auch für Siliziumkonzentrationen über 5 mg/m3 angewendet werden.
Analyse du gaz naturel - Teneur en silicium du biométhane - Partie 1: Détermination de la teneur totale en silicium par spectrométrie d’émission atomique (SEA) (ISO 2613-1:2023)
Le présent document s'applique à la mesure de la teneur en silicium total dans des matrices gazeuses telles que le biométhane et le biogaz. Le silicium est présent sous forme gazeuse, et contenu principalement dans des composés de siloxane, le triméthylsilane et le triméthylsilanol. La forme analytique du silicium mesurée dans la phase liquide après échantillonnage et dérivatisation, est un anion hexafluorosilicate soluble stable dans les milieux légèrement acidifiés. Le silicium total est exprimé sous la forme d'une masse de silicium dans le volume du gaz analysé.
Le présent document s'applique aux matrices gazeuses énoncées, avec des concentrations de silicium allant jusqu'à 5 mg/m3, et concerne principalement les matrices de biométhane avec une teneur en silicium comprise entre 0,1 mg/m3 et 0,5 mg/m3.
Avec une adaptation assurant une efficacité d'absorption appropriée, il peut être utilisé pour des concentrations plus élevées. La limite de détection de cette méthode est estimée à 0,05 mg/m3 pour un volume d'échantillon de gaz de 0,020 m3. Tous les composés présents dans la phase gazeuse sont volatils à la température d'absorption et de dérivatisation, et les composés organosiliciés gazeux sont piégés dans le milieu d'absorption puis dérivés sous forme de silicium analytique qui est mesuré selon la présente méthode. La concentration de silicium est mesurée dans le milieu de dérivatisation dilué, par spectrométrie d'émission atomique, après atomisation/ionisation dans un plasma micro-ondes ou à couplage inductif.
Sauf indication contraire, tous les volumes et concentrations sont établis pour des conditions normales (température, 273 K et pression, 101,325 kPa).
NOTE Avec des facteurs de dilution appropriés, la méthode peut également être appliquée à des concentrations de silicium supérieures à 5 mg/m3.
Analiza zemeljskega plina - Vsebnost silicija v biometanu - 1. del: Določevanje celotnega silicija z atomsko emisijsko spektroskopijo (AES) (ISO 2613-1:2023)
Ta dokument se uporablja za določevanje celotnega silicija v plinastih matricah, kot so biometan, bioplin in deponijski plin. Silicij je prisoten v plinski fazi predvsem siloksanovih spojin, trimetilsilana in trimetilsilanola. Analitična oblika silicija, izmerjena v tekoči fazi po izvedenem vzorčenju in postopku derivatizacije, je topni heksafluorosilikatni anion, stabilen v rahlo kislem mediju. Celotni silicij je izražen kot masa silicija v prostornini analiziranega plina.
Ta dokument se uporablja za vse navedene plinaste matrice s koncentracijami silicija do 5 mg/m3 in je pretežno namenjen za matrice biometana z vsebnostjo 0,1 do 0,5 mg/m3. Uporabiti ga je mogoče za višje koncentracije, vendar je v tem primeru priporočljivo preveriti absorpcijsko učinkovitost enot za ustvarjanje mehurčkov/zbiralnikov plinov, preden je mogoče potrditi veljavnost rezultatov. Meja zaznavnosti pri tej metodi je ocenjena na 0,05 mg/m3 na podlagi prostornine vzorca 0,020 m3. Ta metoda se uporablja za merjenje vseh zmesi, prisotnih v plinasti fazi, ki so hlapne pri temperaturi absorpcije in derivatizacije, ter plinastih siloksanov, ujetih v absorpcijskem mediju in derivatiziranih v vrsto analitičnega silicija. Koncentracija silicija se izmeri v razredčenem mediju za derivatizacijo z atomskim emisijskim spektrometrom po atomizaciji/ionizaciji v mikrovalovni plazmi ali induktivno sklopljeni plazmi.
General Information
Standards Content (Sample)
SLOVENSKI STANDARD
01-julij-2023
Analiza zemeljskega plina - Vsebnost silicija v biometanu - 1. del: Določevanje
celotnega silicija z atomsko emisijsko spektroskopijo (AES) (ISO 2613-1:2023)
Analysis of natural gas - Silicon content of biomethane - Part 1: Determination of total
silicon by atomic emission spectroscopy (AES) (ISO 2613-1:2023)
Analyse von Erdgas - Siliziumgehalt von Biomethan - Teil 1: Bestimmung des
Gesamtsiliziumgehalts durch AES (ISO 2613-1:2023)
Analyse du gaz naturel - Teneur en silicium du biométhane - Partie 1: Détermination de
la teneur totale en silicium par spectrométrie d’émission atomique (SEA) (ISO 2613-
1:2023)
Ta slovenski standard je istoveten z: EN ISO 2613-1:2023
ICS:
75.060 Zemeljski plin Natural gas
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.
EN ISO 2613-1
EUROPEAN STANDARD
NORME EUROPÉENNE
May 2023
EUROPÄISCHE NORM
ICS 75.060
English Version
Analysis of natural gas - Silicon content of biomethane -
Part 1: Determination of total silicon by atomic emission
spectroscopy (AES) (ISO 2613-1:2023)
Analyse du gaz naturel - Teneur en silicium du Analyse von Erdgas - Siliziumgehalt von Biomethan -
biométhane - Partie 1: Détermination de la teneur Teil 1: Bestimmung des Gesamtsiliziumgehalts durch
totale en silicium par spectrométrie d'émission AES (ISO 2613-1:2023)
atomique (SEA) (ISO 2613-1:2023)
This European Standard was approved by CEN on 3 May 2023.
CEN members are bound to comply with the CEN/CENELEC Internal Regulations which stipulate the conditions for giving this
European Standard the status of a national standard without any alteration. Up-to-date lists and bibliographical references
concerning such national standards may be obtained on application to the CEN-CENELEC Management Centre or to any CEN
member.
This European Standard exists in three official versions (English, French, German). A version in any other language made by
translation under the responsibility of a CEN member into its own language and notified to the CEN-CENELEC Management
Centre has the same status as the official versions.
CEN members are the national standards bodies of Austria, Belgium, Bulgaria, Croatia, Cyprus, Czech Republic, Denmark, Estonia,
Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway,
Poland, Portugal, Republic of North Macedonia, Romania, Serbia, Slovakia, Slovenia, Spain, Sweden, Switzerland, Türkiye and
United Kingdom.
EUROPEAN COMMITTEE FOR STANDARDIZATION
COMITÉ EUROPÉEN DE NORMALISATION
EUROPÄISCHES KOMITEE FÜR NORMUNG
CEN-CENELEC Management Centre: Rue de la Science 23, B-1040 Brussels
© 2023 CEN All rights of exploitation in any form and by any means reserved Ref. No. EN ISO 2613-1:2023 E
worldwide for CEN national Members.
Contents Page
European foreword . 3
European foreword
This document (EN ISO 2613-1:2023) has been prepared by Technical Committee ISO/TC 193 "Natural
gas" in collaboration with Technical Committee CEN/TC 408 “Natural gas and biomethane for use in
transport and biomethane for injection in the natural gas grid” the secretariat of which is held by
AFNOR.
This European Standard shall be given the status of a national standard, either by publication of an
identical text or by endorsement, at the latest by November 2023, and conflicting national standards
shall be withdrawn at the latest by November 2023.
Attention is drawn to the possibility that some of the elements of this document may be the subject of
patent rights. CEN shall not be held responsible for identifying any or all such patent rights.
This document has been prepared under a Standardization Request given to CEN by the European
Commission and the European Free Trade Association.
Any feedback and questions on this document should be directed to the users’ national standards
body/national committee. A complete listing of these bodies can be found on the CEN website.
According to the CEN-CENELEC Internal Regulations, the national standards organizations of the
following countries are bound to implement this European Standard: Austria, Belgium, Bulgaria,
Croatia, Cyprus, Czech Republic, Denmark, Estonia, Finland, France, Germany, Greece, Hungary, Iceland,
Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Republic of
North Macedonia, Romania, Serbia, Slovakia, Slovenia, Spain, Sweden, Switzerland, Türkiye and the
United Kingdom.
Endorsement notice
The text of ISO 2613-1:2023 has been approved by CEN as EN ISO 2613-1:2023 without any
modification.
INTERNATIONAL ISO
STANDARD 2613-1
First edition
2023-05
Analysis of natural gas — Silicon
content of biomethane —
Part 1:
Determination of total silicon by
atomic emission spectroscopy (AES)
Analyse du gaz naturel — Teneur en silicium du biométhane —
Partie 1: Détermination de la teneur totale en silicium par
spectrométrie d’émission atomique (SEA)
Reference number
ISO 2613-1:2023(E)
ISO 2613-1:2023(E)
© ISO 2023
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
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Phone: +41 22 749 01 11
Email: copyright@iso.org
Website: www.iso.org
Published in Switzerland
ii
ISO 2613-1:2023(E)
Contents Page
Foreword .iv
Introduction .v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Principle . 2
5 Reagents and labware . 2
6 Apparatus . 6
6.1 Sampling and derivatization equipment. . 6
6.2 MWP/ICP-AES instrument. . . 7
6.3 Analytical balance, capable of weighing to the nearest 0,01 mg. . 7
7 Sampling . 7
8 Derivatization . 9
9 Analytical procedure . 9
9.1 Set-up of the equipment . 9
9.2 Calibration line . 10
9.3 Analysis of unknown and QC samples . 10
10 Calculation .10
11 Expression of results .11
12 Precision of the method .11
13 Measurement uncertainty .11
14 Test report .12
Bibliography .13
iii
ISO 2613-1:2023(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 193, Natural gas, Subcommittee SC 1,
Analysis of natural gas, in collaboration with the European Committee for Standardization (CEN)
Technical Committee CEN/TC 408, Biomethane for use in transport and injection in natural gas pipelines,
in accordance with the Agreement on technical cooperation between ISO and CEN (Vienna Agreement).
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
ISO 2613-1:2023(E)
Introduction
This document describes a method for the measurement of the total concentration of silicon in
biomethane, biogas and similar gaseous matrices when used in the natural gas grids and when using it
as a transport fuel. The method is based on using a liquid impinger to accumulate the silicon from a gas
sample, followed by instrumental analysis.
Due to the extensive usage of siloxane compounds, their volatility and great affinity to apolar
environments, siloxanes are considered as one of the most important impurities in biogas. They are
undesired because of their potential for abrasive SiO formation as combustion product that can
damage engines and appliances. Furthermore, some of these compounds present a health risk.
For the purpose of this document, silicon species measured is quoted as total silicon. Silicon measured
is from organosilicon species that are trapped from the gas phase in liquid media and derivatized into
2-
analytical form of hexafluorosilicate (SiF ) ions which remain present in solution when analysed.
v
INTERNATIONAL STANDARD ISO 2613-1:2023(E)
Analysis of natural gas — Silicon content of biomethane —
Part 1:
Determination of total silicon by atomic emission
spectroscopy (AES)
1 Scope
This document is applicable to the measurement of the total silicon content in gaseous matrices such
as biomethane and biogas. Silicon is present in a gas phase contained predominantly in siloxane
compounds, trimethylsilane and trimethylsilanol. The analytical form of the silicon measured in liquid
phase after conducted sampling and derivatization procedure is soluble hexafluorosilicate anion stable
in slightly acidified media. Total silicon is expressed as a mass of silicon in the volume of the analysed
gas.
This document is applicable to stated gaseous matrices with silicon concentrations up to 5 mg/m ,
and it is prevalently intended for the biomethane matrices with Si mass concentration of 0,1 mg/m to
0,5 mg/m .
With adaptation to ensure appropriate absorption efficiency, it can be used for higher concentrations.
3 3
The detection limit of the method is estimated as 0,05 mg/m based on a gas sample volume of 0,020 m .
All compounds present in the gas phase are volatile at the absorption and derivatization temperature
and gaseous organosilicon species are trapped in absorbance media and derivatized into analytical
silicon that is measured by this method. The concentration of the silicon is measured in diluted
derivatization media using atomic emission spectrometry upon atomisation/ionisation in microwave
or inductively coupled plasma.
Unless specified otherwise, all volumes and concentrations refer to standard reference conditions
(temperature, 273 K, and pressure, 101,325 kPa).
NOTE When using appropriate dilution factors, the method can also be applied for silicon concentrations
above 5 mg/m .
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 3696, Water for analytical laboratory use — Specification and test methods
ISO 6143, Gas analysis — Comparison methods for determining and checking the composition of calibration
gas mixtures
ISO 14532, Natural gas — Vocabulary
ISO 10715, Natural gas — Gas sampling
ISO 14912, Gas analysis — Conversion of gas mixture composition data
3 Terms and definitions
For the purposes of this document, the terms and definitions given in ISO 14532 and the following apply.
ISO 2613-1:2023(E)
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 https:// www .electropedia .org/
3.1
siloxane
functional group where two silicon atoms are connected via an oxygen atom
Note 1 to entry: Depending on the substrate used to produce biogas and the process used for purification,
biomethane can contain siloxanes. During combustion, siloxanes can be oxidized to silicon dioxide, an abrasive
compound harmful for mechanical moving parts in e.g. engines and turbines.
3.2
atomic emission spectroscopy
AES
method of chemical analysis that uses the intensity of light emitted from a flame, plasma, arc, or spark
at a particular wavelength to determine the quantity of an element in a sample
4 Principle
WARNING — Persons using this document should be familiar with normal laboratory practice.
This standard does not purport to address all of the safety problems, if any, associated with its
use. It is the responsibility of the user to establish appropriate safety and health practices and to
ensure compliance with any national regulatory conditions.
A methane matrix gas sample (e.g. biomethane, biogas, natural gas and blends thereof) containing
siloxane compounds is passed through liquid absorbent (nitric acid) in serially connected gas bubblers/
impingers to collect the silicon-containing compounds. After sampling of an adequate gas volume,
content of sampling vessels (gas bubblers) is subjected to derivatization by adding hydroxide solution
2-
and hydrofluoric acid in order to obtain silicon in analytical from, hexafluorosilicate (SiF ) anion.
The derivatized sample is analysed for silicon content using an ICP/MWP atomic emission spectrometer
at selected characteristic silicon emission wavelengths using a multipoint calibration using a straight
line obtained from analysing a series of standard silicon solutions.
5 Reagents and labware
To carry out the method, the following reagents shall be of a recognized analytical grade and only
ISO 3696 grade 1 water. If it is visually determined that the reagents have changed their appearance
(colour, consistency, turbidity) they shall be discarded, and fresh ones shall be used.
5.1 Absorber media.
5.1.1 Nitric acid (HNO ), ρ = 1,41 g/ml; 65 % HNO (mass fraction) – for trace elemental
3 (20 ˚C) 3
analysis.
CAUTION — This chemical is especially dangerous if used outside specialized laboratory
conditions. Tests have been performed in which other non-oxo mineral acids (HCl) have been
used, but they have been shown to be inadequate for the absorption of siloxanes from the
gas phase. Special precautions are to be taken when handling this chemical in lab and field
conditions.
ISO 2613-1:2023(E)
5.2 Derivatization media.
5.2.1 Sodium hydroxide pellets, for the preparation of 8 mol/l – 10 mol/l hydroxide solution.
Accurately weigh an appropriate amount of sodium hydroxide pellets and dissolve these in an
appropriate amount of reagent water (5.3). As an example for 100 ml of 10 mol/l sodium hydroxide
solutions, weigh 40 g of sodium hydroxide pellets and dissolve in 100 ml water.
Potassium hydroxide can also be used, but sodium hydroxide is preferred due to operation safety.
WARNING — Reaction of dissolving sodium hydroxide in water is highly exothermic! Heat will be
released and care should be taken when handling the reaction. Add pellets slowly to the water
and cool the dissolution vessel until the dissolution is complete.
5.2.2 Hydrofluoric acid (HF), ρ = 1,16 g/ml; 48 % HF (mass fraction).
(20 ˚C)
WARNING — Hydrofluoric acid is a very toxic acid and penetrates the skin and tissues deeply
if not treated immediately. Injury occurs in two stages: firstly, by hydration that induces tissue
necrosis; and secondly, by penetration of fluoride ions deep into the tissue and thereby reacting
with calcium. Boric acid and/or other complexing reagents and appropriate treatment agents
should be administered immediately. Consult appropriate safety literature for determining the
proper protective eyewear, clothing and gloves to use when handling hydrofluoric acid. Always
have appropriate treatment materials readily available prior to working with this acid.
CAUTION — This chemical is especially dangerous if used outside specialized laboratory
conditions. Tests have been performed in which other fluoride donor derivatization reagents
(NaF) have been used, but they have been shown to be inadequate for the derivatization of
absorbed siloxanes from the gas phase. Special precautions are to be taken when handling this
chemical in lab and field conditions
5.3 Water, complying with grade 1 of ISO 3696.
5.4 Pure siloxane compounds.
Linear siloxanes Molecular formula Cyclic siloxanes Molecular formula
Hexamethyldisiloxane – L2 C H OSi Hexamethylcyclotrisiloxane - D3 C H O Si
6 18 2 6 18 3 3
Octamethyltrisiloxane – L3 C H O Si Octamethylcyclotetrasiloxane C H O Si
8 24 2 3 8 24 4 4
- D4
Decamethyltetrasiloxane C H O Si Decamethylcyclopentasiloxane C H O Si
10 30 3 4 10 30 5 5
– L4 - D5
Dodecamethylpentasiloxane C H O Si Dodecamethylcyclohexasilox- C H O Si
12 36 4 5 12 36 6 6
– L5 ane - D6
Use at least one representative of chain and one representative of cyclic siloxane compounds for the
purpose of performing initial and regular quality control of the method validity.
5.5 pH colour-fixed indicator strips, pH range from 0 to 14, or, alternatively, a pH meter with HF
resistant electrode.
5.6 Calibration solutions.
5.6.1 General
The following procedure for the preparation of standard and calibration solutions of silicon is adjusted
to the lower range of silicon concentration in gas sample. If higher concentrations of silicon shall be
measured, adjust the concentrations of the working standard and calibration solutions accordingly.
ISO 2613-1:2023(E)
When determining silicon in aqueous samples, only plastic, PTFE or quartz labware shall be used from
time of sample collection to completion of analysis.
5.6.2 Certified ICP-Si stock standard solution.
Example of certified Si standard solution is water solution (only trace level of HF is acceptable) with Si
mass concentration of 10 000 μg/ml and relative expanded uncertainty (coverage factor k = 2) 0,5 %.
This concentration is used in the example of the Si standard solution preparation in 5.6.3.
Certified Si stock standard solutions of other concentrations can also be used. Adjust the procedure for
preparing standard solution accordingly.
If Si stock standard solution is prepared in-house gravimetrically from salt-containing silicon, apply
required statistical procedure for obtaining accurate concentration accompanied with uncertainty
value.
NOTE References [1][2] provide guidance.
5.6.3 Si standard solution.
The target Si mass fraction is ρ(Si) ≈ 100 mg/kg. Weigh empty 50 ml plastic volumetric flask using
analytical balance (6.3). Add around 10 ml of 2 % nitric acid (mass fraction). Accurately pipette 0,5 ml
of stock solution (5.6.2) and add it to the plastic volumetric flask. Dil
...
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