EN ISO 18227:2025

SLOVENSKI STANDARD
oSIST prEN ISO 18227:2024
01-november-2024
Trdni matriksi v okolju - Določanje elementne sestave z rentgensko fluorescenčno
spektrometrijo (ISO/DIS 18227:2024)
Environmental solid matrices - Determination of elemental composition by X-ray
fluorescence spectrometry (ISO/DIS 18227:2024)
Feststoffe in der Umwelt - Bestimmung der elementaren Zusammensetzung durch
Röntgenfluoreszenz (ISO/DIS 18227:2024)
Matrices solides environnementales - Détermination de la composition élémentaire par
spectrométrie de fluorescence X (ISO/DIS 18227:2024)
Ta slovenski standard je istoveten z: prEN ISO 18227
ICS:
13.030.10 Trdni odpadki Solid wastes
13.080.10 Kemijske značilnosti tal Chemical characteristics of
soils
oSIST prEN ISO 18227:2024 en,fr,de
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

oSIST prEN ISO 18227:2024
oSIST prEN ISO 18227:2024
DRAFT
International
Standard
ISO/DIS 18227
ISO/TC 190/SC 3
Environmental solid matrices —
Secretariat: DIN
Determination of elemental
Voting begins on:
composition by X-ray fluorescence
2024-09-23
spectrometry
Voting terminates on:
ICS: 13.080.10
2024-12-16
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Reference number
ISO/DIS 18227:2024(en)
oSIST prEN ISO 18227:2024
DRAFT
ISO/DIS 18227:2024(en)
International
Standard
ISO/DIS 18227
ISO/TC 190/SC 3
Environmental solid matrices —
Secretariat: DIN
Determination of elemental
Voting begins on:
composition by X-ray fluorescence
spectrometry
Voting terminates on:
ICS: 13.080.10
THIS DOCUMENT IS A DRAFT CIRCULATED
FOR COMMENTS AND APPROVAL. IT
IS THEREFORE SUBJECT TO CHANGE
AND MAY NOT BE REFERRED TO AS AN
INTERNATIONAL STANDARD UNTIL
PUBLISHED AS SUCH.
This document is circulated as received from the committee secretariat.
IN ADDITION TO THEIR EVALUATION AS
BEING ACCEPTABLE FOR INDUSTRIAL,
© ISO 2024
TECHNOLOGICAL, COMMERCIAL AND
USER PURPOSES, DRAFT INTERNATIONAL
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Published in Switzerland Reference number
ISO/DIS 18227:2024(en)
ii
oSIST prEN ISO 18227:2024
ISO/DIS 18227:2024(en)
Contents Page
Foreword .iv
Introduction .v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Safety remarks . 3
5 Principle . 3
6 Apparatus . 3
7 Reagents . 4
8 Interferences and sources of error . 5
9 Sample preparation . 5
9.1 General .5
9.2 Drying and determination of dry mass .5
9.3 Preparation of pressed pellet .6
9.4 Preparation of fused beads .6
10 Procedure . 7
10.1 Analytical measurement conditions .7
10.1.1 Wavelength dispersive instruments .7
10.1.2 Intensities and background corrections .7
10.1.3 Counting time .7
10.1.4 Energy dispersive instruments .7
10.1.5 Intensities and background corrections .7
10.2 Calibration .8
10.2.1 General .8
10.2.2 General calibration procedure .8
10.2.3 Internal standard correction using Compton (incoherent) scattering method .8
10.2.4 Fundamental parameter approach .9
10.2.5 Fundamental or theoretical influence coefficient method .9
10.2.6 Empirical alpha correction.10
10.2.7 Calibration procedure for trace elements using the pressed pellet method .10
10.2.8 Calibration procedure for major and minor oxides using the fused bead method . 12
10.3 Analysis of the samples . 13
11 Quality control .13
11.1 Drift correction procedure . 13
11.2 Blank test . 13
11.3 Reference materials . 13
12 Calculation of the result . 14
13 Test report . 14
Annex A (informative) Semi-quantitative screening analysis of waste, sludge and soil samples .15
Annex B (informative) Examples for operational steps of the sample preparation for soil and
waste samples .18
Annex C (informative) Suggested analytical lines, crystals and operating conditions .23
Annex D (informative) List of reference materials applicable for XRF analysis .25
Annex E (informative) Validation .26
Bibliography .36

iii
oSIST prEN ISO 18227:2024
ISO/DIS 18227:2024(en)
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 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).
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/had not] received notice of
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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 190, Soil quality, Subcommittee SC 3, Chemical
and physical characterization.
This second edition cancels and replaces the first edition (ISO 18227:2014), which has been technically
revised.
The main changes compared to the previous edition are as follows:
— the contents of the two almost identical standards ISO 18277:2014 and EN 15309:2007 have been
combined;
— normative references have been revised.
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
oSIST prEN ISO 18227:2024
ISO/DIS 18227:2024(en)
Introduction
X-ray fluorescence spectrometry is a fast and reliable method for the quantitative analysis of the total
content of certain elements within different matrices.
The quality of the results obtained depends very closely on the type of instrument used, e.g. bench top
or high performance, energy dispersive or wavelength dispersive instruments. When selecting a specific
instrument several factors have to be considered, such as the matrices to be analysed, elements to be
determined, detection limits required and the measuring time. The quality of the results depends on the
element to be determined and on the surrounding matrix.
Due to the wide range of matrix compositions and the lack of suitable reference materials in the case of
inhomogeneous matrices such as waste, it is generally difficult to set up a calibration with matrix- matched
reference materials.
Therefore this standard describes two different procedures:
— a quantitative analytical procedure for homogeneous solid waste, soil and soil-like material in the
normative part. The calibration is based on matrix-matched standards;
— an XRF screening method for solid and liquid material as waste, sludge and soil in Annex A which
provides a total element characterization at a semi-quantitative level. The calibration is based on matrix-
independent calibration curves, previously set up by the manufacturer.

v
oSIST prEN ISO 18227:2024
oSIST prEN ISO 18227:2024
DRAFT International Standard ISO/DIS 18227:2024(en)
Environmental solid matrices — Determination of elemental
composition by X-ray fluorescence spectrometry
1 Scope
This document specifies the procedure for a quantitative determination of major and trace element
concentrations in homogeneous solid waste, soil, soil-like material and sludge by energy dispersive X-ray
fluorescence (EDXRF) spectrometry or wavelength dispersive X-ray fluorescence (WDXRF) spectrometry
using a calibration with matrix-matched standards.
This document is applicable for the following elements: Na, Mg, Al, Si, P, S, Cl, K, Ca, Ti, V, Cr, Mn, Fe, Co, Ni,
Cu, Zn, As, Se, Br, Rb, Sr, Y, Zr, Nb, Mo, Ag, Cd, Sn, Sb, Te, I, Cs, Ba, Ta, W, Hg, Tl, Pb, Bi, Th and U. Concentration
levels between approximately 0,000 1 % and 100 % can be determined depending on the element and the
instrument used.
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 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
absorption edge
jump of the mass absorption coefficient at a specific wavelength or energy
3.2
absorption of X-rays
loss of intensity of X-rays by an isotropic and homogenous material as described by the Bouger-Lambert law
3.3
analytical line
specific characteristic X-ray spectral line of the atom or ion of the analyte used for determination of the
analyte content
3.4
continuous radiation
electromagnetic radiation produced by the acceleration of a charged particle, such as an electron, when
deflected by another charged particle, such as an atomic nucleus
3.5
Compton-line
spectral line due to incoherent scattering (Compton-effect) occurring when the incident X-ray photon strike
an atom without promoting fluorescence
Note 1 to entry: Energy is lost in the collision and therefore the resulting scattered X-ray photon is of lower energy
than the incident X-ray photon.

oSIST prEN ISO 18227:2024
ISO/DIS 18227:2024(en)
3.6
drift correction monitor
physically stable sample used to correct for instrumental drift
3.7
emitted sample X-rays
radiation emitted by sample consisting of X-ray fluorescence radiation and scattered primary X-rays
3.8
fused bead
analyte sample prepared by dissolution in a flux
3.9
liquid sample
analyte sample submitted as a solution for direct measurement in the sample cup
3.10
mass absorption coefficient
constant describing the fractional decrease in the intensity of a beam of X-radiation as it passes through an
absorbing medium
Note 1 to entry: This is expressed in units of cm /g.
Note 2 to entry: The mass absorption coefficient is a function of the wavelength of the absorbed radiation and the
atomic number of the absorbing element.
3.11
polarized excitation X-ray spectrometer
energy dispersive X-ray spectrometer where the excitation is performed by polarized radiation and the
emitted X-ray fluorescence radiation is detected along the direction of polarization
3.12
powder sample
analyte sample submitted as a powder for direct measurement in the sample cup
3.13
precision
closeness of agreement of results obtained by applying the method several times under prescribed conditions
[SOURCE: ISO 5725-2:2019, x.xx]
3.14
pressed pellet
analyte sample prepared by pressing milled material into a disk
3.15
primary X-ray
X-ray by which the sample is radiated
3.16
quality control sample
stable sample with known contents, e.g. certified reference material (CRM) used to monitor instrument and
calibration performance
3.17
X-ray fluorescence radiation
emission of characteristic X-rays from a sample that has been bombarded by high-energy X-rays or gamma rays

oSIST prEN ISO 18227:2024
ISO/DIS 18227:2024(en)
4 Safety remarks
Anyone dealing with waste and sludge analysis has to be aware of the typical risks that this kind of material
presents irrespective of the parameter to be determined. Waste and sludge samples can contain hazardous
e.g. toxic, reactive, flammable, and infectious substances, which could potentially undergo biological and/
or chemical reaction. Consequently, it is recommended that these samples should be handled with special
care. The gases that can be produced by microbiological or chemical activity are potentially flammable and
pressurize sealed bottles. Bursting bottles are likely to result in hazardous shrapnel, dust and/or aerosol.
National regulations should be followed with respect to all hazards associated with this method.
The X-ray fluorescence spectrometer shall comply with European/international and national regulations
relevant to radiation protection.
The person responsible for managing or supervising the operation of X-ray equipment shall provide evidence
of his knowledge of radiation protection according to national regulations.
5 Principle
After a suitable preparation, if necessary, the sample is introduced into an XRF-spectrometer and excited
by primary X-rays. The intensities of the secondary fluorescent energy lines specific for each element are
measured and the elemental composition of the sample is determined by reference to previously established
calibration graphs or equations and applying corrections for inter-element effects. The calibration equations
and inter-element corrections are established using pure reagents and/or series of internal or reference
materials providing they meet all the requirements of the relevant preparation technique.
6 Apparatus
6.1 X-ray fluorescence spectrometer, shall be able to analyse the elements according to the scope of this
document.
The following types of X-ray fluorescence spectrometers are applicable:
— energy dispersive X-ray fluorescence (EDXRF) spectrometer that achieves the dispersion of the emitted
X-ray fluorescence radiation by an energy dispersive detector;
— wavelength dispersive X-ray fluorescence (WDXRF) spectrometer that achieves the dispersion of the
emitted X-ray fluorescence radiation by diffraction by a crystal or a synthetic multilayer.
The spectrometer consists of a number of components:
— primary X-ray source, an X-ray tube with a high voltage generator;
— a sample holder;
— detector unit including electronic equipment;
— source modifiers to modify the shape or intensity of the source spectrum or the beam shape (such as
source filters, secondary targets, polarizing targets, collimators, focussing optics, etc.).
The detector unit is different for WDXRF and for EDXRF spectrometers. WDXRF spectrometers take
advantage of the dispersion of the emitted radiation by scattering by a crystal or a synthetic multilayer.
The detector does not need to be capable of energy discrimination. EDXRF spectrometers use an energy
dispersive detector. Pulses of current from the detector, which are a measure of the energy of the incoming
X-rays, are segregated into channels according to energy using a multi-channel analyser (MCA). The
spectrometer is capable to measure under vacuum, helium-atmosphere (7.3) or nitrogen- atmosphere (7.4).
NOTE 1 The use of a high-energy X-ray tube increases the potential for losses of volatile analytes from samples by
heating in the spectrometer during analysis.

oSIST prEN ISO 18227:2024
ISO/DIS 18227:2024(en)
NOTE 2 The new generation of EDXRF spectrometers takes advantage of the polarizing target theory resulting in a
significant decrease of the background scattering, and therefore lower limits of detection can be achieved (comparable
to WDXRF).
6.2 Analytical balance, readable and accurate to 0,001 g.
6.3 Drying oven, thermostatically controlled and capable of maintaining a temperature of (105 ± 5) °C.
6.4 Grinding mill, capable of grinding dried materials to a required particle size without contaminating
the samples with compounds to be determined, preferable with walls made of agate, corundum or zircon.
6.5 Pellet preparation equipment, manual or automatic pellet press, capable of providing a pressure of
at least 100 kN.
6.6 Aluminium cup: supporting backing cup for pressed pellets.
6.7 Fusion apparatus: electric, gas or high frequency induction furnace that can be heated up to a fixed
temperature of between 1 000 °C and 1 250 °C.
6.8 Fusion crucibles: crucibles made of non-wetting platinum alloy (Pt 95 %; Au 5 % is suitable).
Lids, if used, shall be made from platinum alloy.
NOTE Certain metal sulphides (so called platinum poisons) affect the platinum crucibles in which the sample
is melted.
6.9 Casting moulds: non-wetting platinum alloy (Pt 95 %; Au 5 % is suitable).
7 Reagents
The reagents mentioned are used as carrier material.
7.1 Binder: liquid or solid binder free of analytes of interest.
Solid materials can contain a certain amount of moisture, which shall be compensated for.
NOTE Different type of binders may be used. A binder commonly used is wax.
7.2 Flux: solid flux free of analytes of interest.
Solid materials can contain a certain amount of moisture, which shall be compensated for (e.g. ISO 12677 for
compensation for moisture in flux).
NOTE Different type of fluxes may be used. Fluxes commonly used are lithium metaborate, lithium tetraborate or
mixtures of both.
7.3 Helium, purity ≥ 99,996 %.
7.4 Nitrogen, purity ≥ 99,996 %.

oSIST prEN ISO 18227:2024
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8 Interferences and sources of error
The container in which the sample is delivered and stored can be a source of error. Its material shall be
chosen according to the elements to be determined.
NOTE Elemental Hg can penetrate polyethylene walls very rapidly in both directions. In the case of glass
containers, contamination can be observed for some elements e.g. Al, As, Ba, Ce, K, Na and Pb.
Interferences in X-ray fluorescence spectrometry are due to spectral line overlaps, matrix effects, spectral
artefacts and particle size or mineralogical effects.
Spectral line overlaps occur when an analytical line cannot be resolved from the line of a different element.
Corrections for these interferences are made using the algorithms provided with the software.
Matrix effects occur when the X-ray fluorescence radiation from the analyte element is absorbed or enhanced
by other elements in the sample before it reaches the detector. In the case of complex matrices these effects
generally have to be corrected.
Spectral artefacts e.g. escape peaks, sum peaks, pulse pile up lines, dead time, and continuous radiation
correction, are accounted for by the provided software. Spectral artefacts differ for energy dispersive and
wavelength dispersive XRF spectrometry.
Particle size effects can be reduced by milling the sample, and both particle size and mineralogical effects
can be eliminated by preparing bead samples. It is vital for quantitative analysis that the same sample
preparation procedure is applied to both the standards and the samples to be analysed.
9 Sample preparation
9.1 General
In analysis by XRF spectrometry the sample preparation step is crucial as the quality of the sample
preparation strongly influences the accuracy of the results.
For quantitative analysis of solid samples, pressed pellets or fused beads have to be prepared. The application
of the pressed pellet method is recommended for the quantification of trace elements and mandatory for the
quantification of volatile elements, and the fused bead method for the determination of non-volatile major
and minor elements.
NOTE 1 The preparation of fused beads eliminates effects due to particle size and mineralogy.
The conditions of the preparation of fused beads shall be adapted to the matrix properties. Otherwise the
preparation of fused beads can be difficult or can cause problems in case of waste-like matrices such as
sludges.
For a given calibration the same preparation method shall be used throughout, for both samples and
standards.
NOTE 2 Depending on the sample type other sample preparation methods can be applied according to Annex B.
For precise quantitative measurements, homogeneous and representative test portions are necessary. If not
otherwise specified, pre-treatment and preparation of test portions should be carried out according to the
appropriate clauses of e.g. ISO 11464, EN 15002 or EN 16179. The particle size of the sample can strongly
affect the precision of the measurement. The particle size should preferably be smaller than 150 µm.
NOTE 3 Particle size smaller than 80 µm is recommended for the analysis of low atomic mass elements when using
the pressed pellet method.
9.2 Drying and determination of dry mass
If not otherwise specified, the determination of the dry mass should be carried out according to e.g.
ISO 11465 or EN 15934.
oSIST prEN ISO 18227:2024
ISO/DIS 18227:2024(en)
9.3 Preparation of pressed pellet
After drying (6.3) and milling or grinding the sample (6.4), a pellet is prepared in the pellet press (6.5).
Before pressing, the sample shall be mixed and homogenized with a binder (7.1) in a ratio of sampler: binder
of 10:1 by weight. For the preparation of 40 mm in diameter pellets, about 10,0 g of sample is taken; for
32 mm in diameter pellets about 4,5 g of sample is required. The amount of binder in the pellet shall be
taken into account for the dilution factor. It is recommended to press the sample in an aluminium cup (6.6)
as support.
NOTE 1 Different types of binders can be used. A binder commonly used is wax. In the case of a liquid binder the
pellet is placed in an oven to evaporate organic solvent.
NOTE 2 Different dilution factors can be used.
9.4 Preparation of fused beads
After drying (6.3) and milling or grinding the sample (6.4), a fused bead is prepared using the fusion
apparatus (6.7).
Ignite the sample at 1 025 °C ± 25 °C until constant mass is reached. Determine the loss on ignition at the chosen
temperature to correct for volatile elements and/or compounds being released during ignition of the sample.
NOTE 1 The ignition temperature can vary depending on the sample matrix.
Because of the wide applicability of the fused bead technique, various fluxes and modes of calibration are
permitted providing they have been demonstrated to be able to meet certain criteria of reproducibility,
sensitivity and accuracy.
For application of alkaline fusion technique (e.g. selection of flux, fusion temperature, and additives) e.g.
ISO 14869-2 or CEN/TR 15018 should be used.
NOTE 2 Fluxes commonly used are lithium metaborate, lithium tetraborate or mixtures of both.
NOTE 3 Loss of volatile elements, e.g. As, Br, Cd, Cl, Hg, I, S, Sb, Se, and Tl can occur during the fusion process. Also,
Cu can be volatile if a bromide-releasing agent is used.
The flux (7.2) is added to the ignited material in a dilution ratio of sample: flux of 1:5 by weight. For the
preparation of 40 mm in diameter beads, about 1,6 g of ignited sample is taken; for 32 mm in diameter beads
about 0,8 g of ignited sample is required. The amount of flux in the bead shall be taken into account for the
dilution factor. The same sample preparation procedure and ratio of sample to flux shall be used for samples
and standards. The beads produced should be visually homogeneous and transparent.
NOTE 4 Non-ignited material can be used to prepare beads but, nevertheless, loss of ignition needs to be determined
and needs to be taken into account in the calculation of the results. It should be noted that non-ignited material can
contain compounds that can damage the platinum crucibles during fusion.
NOTE 5 Different dilution factors can be used.
After fusion in a platinum-gold crucible (6.8) the melt is poured into a casting mould (6.9) to make a bead.
Beads can deteriorate because of adverse temperature and humidity conditions, so it is recommended that
beads are stored in desiccators.

oSIST prEN ISO 18227:2024
ISO/DIS 18227:2024(en)
10 Procedure
10.1 Analytical measurement conditions
10.1.1 Wavelength dispersive instruments
The analytical lines to be used and the suggested operating conditions are given in Table C.1. The settings
are strongly dependent on the spectrometer configuration, e.g. the type of X-ray tube (Rh, Cr), tube power,
available crystals, and type of collimators.
10.1.2 Intensities and background corrections
For the determination of trace elements the measured intensities have to be background-corrected. The
measured background positions should be free of spectral line interferences. The net peak intensity I,
expressed as the number of counts per second of the element of interest, is calculated as the difference
between the measured peak intensity of the element and the background intensity:
II=− I (1)
pb
where
I
is the count rate of the element i, expressed as the number of counts per second;
p
I
is the background count rate of the element i, expressed as the number of counts per second.
b
10.1.3 Counting time
The minimum counting time is the time necessary to achieve an uncertainty (2σ %), which is less than the
desired precision of the measurement. Choose a reference material with a concentration level in the middle
of the working range and measure the count rate. The counting time for each element can be calculated
according to Formula (2):
100 1
t =⋅ (2)
2σ%
II−
pb
where
t
is the total counting time for the peaks and background, in seconds; 2σ% ;

2σ%
is the relative target precision at a confidence level of 95 %, expressed as percentage.
10.1.4 Energy dispersive instruments
The analytical lines to be used and the suggested operating conditions are given in Table C.2. The settings
are strongly dependent on the spectrometer configuration, e.g. type of X-ray tube (Rh, Pd), tube power,
available targets, and type of filters.
10.1.5 Intensities and background corrections
Deconvolution of the spectra and background correction are needed when analysing the samples with
overlapping lines. Usually, XRF instruments are supplied with a specific software module for that purpose.

oSIST prEN ISO 18227:2024
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10.2 Calibration
10.2.1 General
The calibration procedure is similar for energy dispersive and wavelength dispersive techniques. In general
calibration is established by using matrix-adapted reference materials. The calibration equations and inter-
element corrections are calculated by the software of the instrument. An accuracy check is performed with
CRMs or samples with known composition.
Different procedures for correcting matrix effects can be used according to the analytical accuracy required:
— the scattered radiation method is based on the principle that the intensities of the analyte line and of
the Compton line are affected in the same proportion due to the overall mass absorption coefficient of
the sample. This linear relationship holds when all analytes are at low concentrations (trace elements)
and their absorption coefficients are not affected by an adjacent absorption edge. In this case an internal
Compton correction can be used. Aside from that, a correction method using the Compton intensity
with mass absorption coefficients (MAC) is also applicable. In this method, the intensities of the major
elements are measured to apply a jump edge correction for the analysed trace elements;
— correction using the fundamental parameter approach;
— correction using theoretical correction coefficients (alphas) taking basic physical principles, instrumental
geometry etc. into account;
— correction using empirical correction coefficients (alphas) based on regression analysis of standards
with known elemental concentrations.
10.2.2 General calibration procedure
For calibration purposes the measurement of analyte lines of samples of known composition is needed.
Formula (3) implies a linear relationship between the intensity and the concentration.
Ca=+aI⋅ (3)
ii,,01ii
where
C
is the concentration of the element of interest, expressed as mg/kg or percentage dry matter;
i
a
is the offset of the calibration curve;
i,0
a
is the slope of the calibration curve;
i,1
I
is the net intensity of the element of interest, expressed as counts per second.
i
Matrix effects have to be taken into account in X-ray spectrometry according to Formula (4):
Ca=+aM⋅ (4)
ii,,01i
where, M is the correction term due to the matrix effects.
The matrix effect correction term can consist of an internal standard Compton correction method or can be
calculated from mathematical models.
10.2.3 Internal standard correction using Compton (incoherent) scattering method
The measured intensity of incoherent scattering can be used directly to compensate for matrix effects or
indirectly for the determination of the effective mass absorption coefficient μ to correct for matrix effects.
The compensation for matrix effects is based on a combination of sample preparation and experimental
intensity data but not on fundamental and experimental parameters.

oSIST prEN ISO 18227:2024
ISO/DIS 18227:2024(en)
The Compton scatter method can be expressed as:
 I   I 
incr, iu,
CC=⋅ ⋅ (5)
   
iu,,i r
I I
ir, incu,
   
where
C
is the concentration of the element of interest i of the sample, expressed as mg/kg or percentage
iu,
dry matter;
C
is the concentration of the element of interest i of the calibration reference material, expressed as
i ,r
mg/kg or percentage dry matter;
I
is the intensity of the incoherent Compton-line element of the calibration reference material, ex-
incr,
pressed as counts per second;
I
is the intensity of the element of interest i of the calibration reference material, expressed as counts
ir,
per second;
I
is the intensity of the element of interest i of the sample, expressed as counts per second;
iu,
I
is the intensity of the incoherent Compton-line of the sample, expressed as counts per second.
incu,
10.2.4 Fundamental parameter approach
The fundamental parameter approach uses the physical processes forming the basis of X-ray fluorescence
emission and scattering to construct a theoretical model for the correction of matrix effects in practice.
The correction term M is calculated from first principle expressions. These are derived from basic X-ray
physics and contain physical constants and parameters that include absorption and scattering coefficients,
fluorescence yield, primary spectral distributions and spectrometry geometry. The use of scattered
radiation (Compton and/or Rayleigh) allows the determination of matrix effects caused by sample elements
that cannot be measured directly. The calculation of analyte concentrations in samples is based on making
successively better estimates of composition by an iteration procedure. These iteration cycles are performed
until the difference between the compared results is below a defined value.
NOTE The algorithm used for the procedure is usually implemented in the manufacturer’s software.
10.2.5 Fundamental or theoretical influence coefficient method
The fundamental influence coefficient method encompasses any mathematical expression relating emitted
intensities and concentrations in which the influence coefficients are defined and derived explicitly in terms
of fundamental parameters.
The calculation of the concentration from the intensities is performed by linear regression whereby the net
intensities are corrected for the present matrix effects. For each element the concentration is calculated
according to Formulae (6) and (7):
 
C
 i,r 
C = ⋅⋅IM (6)
iu, iu,
 
I
 
ir, 1+ α C
( ∑ ij jr )
j
 
 
 
C
 
i,r
 
C = ⋅⋅IC1+ α (7)
iu, iu, ij ju
  ∑
I  
 
j
ir, 1+ α C  
( ∑ ij jr )
j
 
oSIST prEN ISO 18227:2024
ISO/DIS 18227:2024(en)
where
C
is the concentration of the element of interest i of the sample, expressed as mg/kg or percentage
iu,
dry matter;
C
is the concentration of the element of interest i of the calibration reference material, expressed as
i ,r
mg/kg or percentage dry matter;
I
is the intensity of the incoherent Compton-line of the sample, expressed as counts per second;
ir,
I
is the intensity of the element of interest i of the sample, expressed as counts per second;
iu,
C
is the concentration of the matrix element j of the calibration reference material, expressed as mg/
jr
kg or percentage dry matter;
C
is the concentration of the matrix element j of the sample, expressed as mg/kg or percentage dry
ju
matter;
M is the matrix correction term;
α
is the correction coefficient (called alphas) calculated from theory, although some approximations
ij
are involved.
Different types of alpha coefficient exist, but all of them are calculated without reference to experimental
data; they are calculated using intensity data resulting from a fundamental parameter expression. The alpha
coefficients vary as a function of sample composition and are calculated by an iterative process.
10.2.6 Empirical alpha correction
Empirical alphas are obtained experimentally using the regression analysis of data from reference materials
in which the elements to be measured are known and the total concentration range is covered. Best results
are achieved when the samples and reference materials are of similar composition. Thus, empirical alphas
are based strictly on experimental data and do not take fundamental and instrumental parameters into
account. Different models can be applied, but generally they are based on Formulae 6 and 7, where the
correction term for matrix effects is a function of concentrations.
The empirical alphas are only applicable for a limited concentration range and a well-defined analytical
method where the matrices of samples and standards are similar. The reference materials used should
contain each analyte together with fairly wide concentration ranges of each matrix element. Poor analytical
results are obtained when inappropriate combinations of analytes are chosen. A large number of reference
materials have to be analysed to define the alphas (rule of thumb: minimum of 3 times the number of
parameters to be calculated).
10.2.7 Calibration procedure for trace elements using the pressed pellet method
The pressed pellet method is used to determine the concentrations of trace elements.
Select calibration standards with a similar composition as the samples under investigation containing
the elements of interest and covering the concentration range of interest. The use of reference materials
from different recognized producers is recommended (
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