SIST EN 13656:2020

SLOVENSKI STANDARD
01-december-2020
Nadomešča:
SIST EN 13656:2004
Tla, obdelani biološki odpadki, blato in odpadki - Razklop z zmesjo klorovodikove
kisline (HCl), dušikove(V) kisline (HNO3) in tetrafluoroborove kisline (HBF4) ali
fluorovodikove kisline (HF) za določevanje elementov
Soil, treated biowaste, sludge and waste - Digestion with a hydrochloric (HCl), nitric
(HNO3) and tetrafluoroboric (HBF4) or hydrofluoric (HF) acid mixture for subsequent
determination of elements
Boden, behandelter Bioabfall, Schlamm und Abfall - Aufschluss mit einem Gemisch aus
Salzsäure (HCl), Salpetersäure (HNO3) und Tetrafluorborsäure (HBF4) oder
Fluorwasserstoffsäure (HF) für die anschließende Bestimmung der Elemente
Sols, bio-déchets traités, boues et déchets - Digestion par un mélange d’acides
chlorhydrique (HCl), nitrique (HNO3) et tétrafluoroborique (HBF4) ou fluorhydrique (HF)
pour la détermination ultérieure des éléments
Ta slovenski standard je istoveten z: EN 13656:2020
ICS:
13.030.40 Naprave in oprema za Installations and equipment
odstranjevanje in obdelavo for waste disposal and
odpadkov treatment
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

EN 13656
EUROPEAN STANDARD
NORME EUROPÉENNE
November 2020
EUROPÄISCHE NORM
ICS 13.030.40 Supersedes EN 13656:2002
English Version
Soil, treated biowaste, sludge and waste - Digestion with a
hydrochloric (HCl), nitric (HNO ) and tetrafluoroboric
(HBF ) or hydrofluoric (HF) acid mixture for subsequent
determination of elements
Sols, bio-déchets traités, boues et déchets - Digestion Boden, behandelter Bioabfall, Schlamm und Abfall -
par un mélange d'acides chlorhydrique (HCl), nitrique Aufschluss mit einem Gemisch aus Salzsäure (HCl),
(HNO ) et tétrafluoroborique (HBF ) ou fluorhydrique Salpetersäure (HNO ) und Tetrafluorborsäure (HBF )
3 4 3 4
(HF) pour la détermination ultérieure des éléments oder Fluorwasserstoffsäure (HF) für die anschließende
Bestimmung der Elemente
This European Standard was approved by CEN on 21 September 2020.

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, Turkey and
United Kingdom.
EUROPEAN COMMITTEE FOR STANDARDIZATION
COMITÉ EUROPÉEN DE NORMALISATIO N

EUROPÄISCHES KOMITEE FÜR NORMUN G

CEN-CENELEC Management Centre: Rue de la Science 23, B-1040 Brussels
© 2020 CEN All rights of exploitation in any form and by any means reserved Ref. No. EN 13656:2020 E
worldwide for CEN national Members.

Content Page
European foreword . 3
Introduction . 4
1 Scope . 5
2 Normative references . 5
3 Terms and definitions . 5
4 Principle . 6
5 Interferences and sources of errors . 7
5.1 General information . 7
5.2 Closed vessel system for microwave digestion . 7
6 Reagents . 7
7 Apparatus . 8
8 Procedure . 9
8.1 General . 9
8.2 Blank test . 9
8.3 Method A: Heating block digestion using HCl, HNO and HBF . 9
3 4
8.4 Method B: Microwave digestion . 10
9 Test report . 12
Annex A (normative) Calibration of the power adjustment . 13
Annex B (informative) Repeatability and reproducibility data – Method A and B1 . 14
Annex C (informative) Repeatability and reproducibility data – Method B2 . 23
Bibliography. 36

European foreword
This document (EN 13656:2020) has been prepared by Technical Committee CEN/TC 444 “Environmental
characterization of solid matrices”, of which the secretariat is held by NEN.
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 May 2021 and conflicting national standards shall be withdrawn at
the latest by May 2021.
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 supersedes EN 13656:2002.
In comparison with EN 13656:2002, the following modifications have been made:
— addition of HBF4 as acid. For safety reasons the use of HBF4 is preferred over HF;
— addition of a heating block digestion procedure;
— addition of a microwave digestion procedure temperature-controlled;
— removal of the microwave digestion with semi-open vessel system.
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, Turkey and the United
Kingdom.
Introduction
The methods specified in this document are providing a multi-element digestion of soil, treated biowaste,
sludge and waste prior to analysis. Elements extractable by this procedure can in many instances be
described as “total”, although this will be sample dependent. On the other hand, they cannot be regarded
as available for leaching, as the extraction procedure is too vigorous to represent natural processes.
This document is validated for several types of matrices as indicated in Table 1.
Table 1 — Matrices for which EN 13656 is validated
Materials used in the validation test Validated for digestion Validated for digestion
with HCl:HNO :HBF with HCl:HNO :HF
3 4 3
(see Annex B) (see Annex C)
City waste incineration ash X X
(BCR176/BCR176R)
Ink waste sludge (organic matrix) X X
Electronic industry sludge (“metallic” X X
matrix)
Sediment X
Coal fly ash X
Steel slag X
Copper slag X
City waste incineration fly ash  X
(“oxidised” matrix)
City waste incineration bottom ash  X
(“silicate” matrix)
Sewage sludge (BCR 146R)  X
WARNING — Persons using this document should be familiar with usual laboratory practice. Most
of the reagents used in this document are extremely corrosive and very toxic. Safety precautions
are absolutely necessary, not only due to the strong corrosive reagents employed, but also to the
high temperature and pressures employed.
The use of laboratory-grade microwave equipment with isolated and corrosion resistant safety
devices is essential. Domestic (kitchen) type microwave ovens should not be used, as corrosion by
acid vapours may compromise the function of the safety devices and prevent the microwave
magnetron from shutting off when the door is open, which could result in operator significant
hazardous exposure to microwave energy.
All procedures should be performed in a fume hood or in closed force-ventilated equipment. By the
use of strong oxidising reagents, the formation of explosive organic intermediates is possible,
especially when dealing with samples with a high organic content. Do not open pressurized vessels
before they have cooled down. Avoid contact with the chemicals and the gaseous reaction products.
IMPORTANT — It is absolutely essential that tests conducted according to this document be carried
out by suitably trained staff. People performing the test should be informed on the specific risks
associated with the use of HBF and HF.
1 Scope
This document specifies three methods for the digestion of soil, treated biowaste, sludge and waste by the
use of an acid mixture composed of hydrochloric (HCl), nitric (HNO ) and tetrafluoroboric (HBF ) or
3 4
hydrochloric (HCl), nitric (HNO ) and hydrofluoric (HF) acid as the digestion solution.
Digestion with these acids is effectively considered as a total decomposition of the sample. Elements
extractable by this procedure can in many instances be described as “total”, although this will be sample
dependent.
This document is applicable for the following elements:
Aluminium (Al), antimony (Sb), arsenic (As), barium (Ba), beryllium (Be), cadmium (Cd), calcium (Ca),
chromium (Cr), cobalt (Co), copper (Cu), iron (Fe), lead (Pb), magnesium (Mg), manganese (Mn), mercury
(Hg), molybdenum (Mo), nickel (Ni), phosphorus (P), potassium (K), selenium (Se), silver (Ag), sodium
(Na), strontium (Sr), sulfur (S), tellurium (Te), thallium (Tl), tin (Sn), titanium (Ti), vanadium (V), and
zinc (Zn).
This document can also be applied for the digestion of other elements, provided the user has verified the
applicability.
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.
EN 15002, Characterization of waste - Preparation of test portions from the laboratory sample
EN 15934, Sludge, treated biowaste, soil and waste - Calculation of dry matter fraction after determination of
dry residue or water content
EN 16179, Sludge, treated biowaste and soil - Guidance for sample pretreatment
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:

— IEC Electropedia: available at http://www.electropedia.org/
— ISO Online browsing platform: available at https://www.iso.org/obp
3.1
digestion
mineralization of the organic matter of a sample and dissolution of its mineral part, more or less completely,
when reacting with a reagent mixture
3.2
dry residue
remaining mass fraction of a sample after a drying process at 105 °C under specified conditions
[SOURCE: EN 15934:2012, 3.1]
3.3
dry matter fraction
(dm)
mass fraction of a sample excluding water expressed as mass fraction calculated by determination of dry
residue or water content
[SOURCE: EN 15934:2012, 3.3]
3.4
laboratory sample
sample intended for laboratory inspection of testing
[SOURCE: EN ISO 11074:2015, 4.3.7]
3.5
sample
portion of material selected from a larger quantity of material
3.6
test portion
quantity of material, of proper size for measurement of the concentration or other property of interest,
removed from the test sample
Note 1 to entry: The test portion may be taken from the laboratory sample directly if no preparation of sample is
required (e.g. with liquids), but usually it is taken from the prepared test sample.
Note 2 to entry: A unit or increment of proper homogeneity, size and fineness, needing no further preparation, may
be a test portion.
[SOURCE: EN ISO 11074:2015, 4.3.15]
3.7
test sample
portion of material resulting from the laboratory sample by means of an appropriate method of sample
pretreatment and having the size (volume/mass) necessary for the desired testing or analysis
[SOURCE: EN ISO 11074:2015, 4.3.16]
4 Principle
A test portion is digested according to one of the following heating procedures:
— Method A: Heating block digestion
— A: Digestion with HCl, HNO and HBF using a heating block at (105 ± 5) °C for 2 h, followed by
3 4
filtration/centrifugation.
— Method B: Microwave digestion
— B1: Digestion with HCl, HNO and HBF using a microwave oven with temperature-controlled
3 4
procedure to an end temperature at (175 ± 5) °C in a closed vessel followed by
filtration/centrifugation.
— B2: Digestion with HCl, HNO and HF using a microwave oven with power-controlled procedure in
a closed vessel followed by filtration/centrifugation.
NOTE Alternatively, microwave digestion with temperature-controlled procedure in a closed vessel can be used,
provided the user has verified the applicability.
Due to safety considerations, the digestion with HCl, HNO and HBF is strongly recommended over the
3 4
much more hazardous digestion using HCl, HNO and HF.
5 Interferences and sources of errors
5.1 General information
The container in which the sample is delivered and stored can be a source of errors. Its material shall be
chosen according to the elements to be determined (e.g. elemental Hg can penetrate polyethylene walls
very rapidly in both directions. Glass can contaminate samples with elements that it contains: - e.g. Na, K,
Al).
Grinding or milling samples includes a risk of contamination of the sample by the environment (air, dust,
wear of milling equipment). Due to elevated temperature, losses of volatile elements/compounds are
possible.
For the determination of elements forming volatile elements/compounds (e.g. Hg, As, Pb), special care has
to be taken at sample pre-treatment.
In the case of filtration of the digested solution, it is necessary to take care that the filtration procedure
does not introduce contaminants.
Ensure that all of the test portion is brought into contact with the acid mixture in the digestion vessel.
Some elements of interest can be lost due to precipitation with ions present in the digest solution, e.g. low
soluble chlorides, fluorides and sulphates.
5.2 Closed vessel system for microwave digestion
The upper limits of mass of the test portion according to the manufacturer's specifications have to be taken
into account.
Very reactive or volatile materials that may create high pressures when heated may cause a venting of the
vessels with potential loss of sample and analytes. The complete decomposition of either carbonates, or
carbon based samples, may cause sufficient pressure to vent the vessel.
After digestion, the vessel shall be cooled to room temperature before opening.
6 Reagents
Use only acids and reagents of recognized analytical grade or verify the content of the elements to be
analysed to avoid high blank values for subsequent analytical measurements. Use a test blank solution
throughout the procedure applying all steps with the same amount of acids, but without a sample.
6.1 Water, e.g. deionized.
6.2 Tetrafluoroboric acid (HBF ), c(HBF ) approximately 6 mol/l, w(HBF ) = 38 % (m/m) to
4 4 4
48 % (m/m).
6.3 Hydrofluoric acid (HF), c(HF) approximately 23 mol/l, w(HF) = 40 % (m/m) to 45 % (m/m).
6.4 Boric acid (B(OH) ), solid.
6.5 Boric acid (B(OH) ) solution, e.g. 4 % (m/m) solution.
Dissolve 40 g of boric acid (6.4) in water and dilute to 1 l of water (6.1).
6.6 Hydrochloric acid, c(HCl) approximately 12 mol/l, w(HCl) = 35 % (m/m) to 37 % (m/m).
6.7 Nitric acid, c(HNO ) approximately 15 mol/l, w(HNO ) = 65 % (m/m) to 70 % (m/m).
3 3
7 Apparatus
Usual laboratory apparatus. All glassware and plastics ware shall be adequately cleaned and stored in order
to avoid any contamination.
Depending on the concentration of the element of interest, particular caution shall be taken with respect to
the cleaning of the vessels.
7.1 Method A: heating block digestion
7.1.1 Digestion tube, 50 ml polypropylene tube with a screw cap from polyethylene.
The material of the tube and screw cap shall be tested in order to be sure that release of elements of interest
does not take place. Other materials and vessels with other volumes than mentioned above are allowed to
be used if suitability has been proven.
7.1.2 Temperature-controlled heating block, heating block able to heat the tube(s) to a temperature
of (105 ± 5) °C.
7.2 Method B: microwave digestion, temperature and/or power-controlled, closed vessels
7.2.1 Digestion vessel, for pressurized microwave digestion, typically of 100 ml volume, reagent-,
temperature- and pressure-resistant and capable of containing the mixture of sample and digest solution.
The vessel shall be suitable for the safe application in the temperature and pressure range applied, capable
of withstanding pressures of at least 3 000 kPa.
Digestion vessels made of modified polytetrafluoroethylene (PTFE) and equipped with a safety pressure
releasing system to avoid explosion of the vessel, shall be used. The inner wall of the vessel shall be inert
and shall not release contaminations to the digest solution.
NOTE It can be necessary to periodically clean the digestion vessels with a suitable surfactant to remove
persistent deposits.
7.2.2 Microwave digestion system, temperature-controlled, corrosion resistant and well ventilated.
All electronics shall be protected against corrosion for safe operation.
Use a laboratory-grade microwave oven with temperature feedback control mechanisms.
The microwave digestion system shall be able to control the temperature with an accuracy of at least ± 5 °C
and automatically adjust the microwave field output power within 2 s of sensing. Temperature sensors
shall be accurate to ± 2 °C, including the final reaction temperature of (175 ± 5) °C. Temperature feedback
control provides the primary performance mechanism for the method. Due to the variability in sample
matrix types and microwave digestion equipment (i.e. different vessel types and microwave designs),
control of the temperature during digestion is important for reproducible microwave heating and
comparable data.
The accuracy of the temperature measurement system shall be periodically tested at an elevated
temperature according to the manufactures instructions. If the temperature deviates by more than 2 °C
from the temperature measured by an external, calibrated temperature measurement system, the
microwave oven temperature measurement system shall be re-calibrated.
7.2.3 Microwave digestion system, power-controlled, corrosion resistant and well ventilated. All
electronics shall be protected against corrosion for safe operation.
The microwave unit shall be able to provide programmable power which can be programmed to
within ± 10 W of the required power. Typical units provide a nominal 600 W to 1 200 W of power. If
necessary (referring to manufactures specifications) calibration of the microwave unit shall be performed
(see Annex A).
The microwave unit shall be designed in a way that guarantees homogeneous heating of the samples.
The microwave unit cavity shall be built in a way that even in case of leakage or explosion of the vessels the
safety of the operators can be guaranteed. Household instruments are not suitable for laboratory use.
The microwave unit shall include a temperature and/or pressure control system.
7.3 Sample containers, plastic and glass containers are both suitable.
7.4 Filter, usually with a pore size of 0,45 µm and resistant to the employed acid mixture.
7.5 Volumetric flasks, usually of nominal capacity of 50 ml or 100 ml.
7.6 Analytical balance, with an accuracy of 1 mg or better.
8 Procedure
8.1 General
Pre-treat, if not otherwise specified, soil, sludge and biowaste samples according to EN 16179 and waste
samples according to EN 15002.
Determine the dry matter content, depending on the matrix of the sample, according to EN 15934.
Pre-treatment should include drying and grain size reduction below a particle size of 250 µm, or
homogenizing by use of a high speed mixer or sonification for liquid samples.
The mass of test portion for a single digestion shall be selected in a way that:
— it is representative for the laboratory sample;
— it complies with the specifications of manufacturer of the digestion unit.
If the required representative test portion exceeds the manufacturers' specifications, the test portion
should be divided into smaller quantities and digested separately. The individual digests should be
combined prior to analysis.
8.2 Blank test
Carry out a reagent blank test digestion in parallel with the determination, using the same procedure and
the same quantities of all the reagents as in the determination, but omitting the test portion. The laboratory
shall define acceptable limits.
NOTE The measurement of a blank is introduced to determine the contribution of the extracting solution,
digestion tube and filter used to the measured value.
8.3 Method A: Heating block digestion using HCl, HNO3 and HBF4
Weigh approximately 0,2 g to 0,5 g of the dried and pre-treated test portion with an accuracy of 0,001 g
and transfer to the digestion tube (7.1.1).
The amount of the test sample depends on the amount of organic matter. The maximum amount of organic
carbon shall not exceed 0,15 g when 8 ml of HCl/HNO mixture is used. Per additional 0,1 g organic carbon
(more than this 0,15 g), 1 ml of additional concentrated HNO (6.7) shall be added before the digestion
process is started.
If necessary, moisten the test portion with a few drops of water (6.1). Add (6,0 ± 0,1) ml hydrochloric acid
(6.6) followed by (2,0 ± 0,1) ml nitric acid (6.7) and (4,0 ± 0,1) ml tetrafluoroboric acid (6.2). Let stand at
room temperature until any effervescence almost ceases to allow for slow oxidation of the organic matter
in the sample.
Turn the screw cap gently (not very tight!) and place the digestion tube on the heating block (7.1.2) and
slowly increase the temperature to (105 ± 5) °C. Keep this temperature during 120 min.
Let the tube cool down to room temperature and add water (6.1) to the volume mark.
If a non-graduated digestion tube is used, transfer quantitatively the solution content into a suitable sized
volumetric flask and add water (6.1) to the volume mark. Alternatively, another procedure can be applied,
such that the adjustment to volume shall be carried out immediately after digestion.
If the measurement solution contains suspended particles which may clog nebulizers or interfere with an
injection of the sample into the instrument, the sample may be centrifuged or filtered (7.4).
If the measurement solution contains suspended particles, the digestion is not complete. This should be
stated in the report.
The measurement solution is now ready for the determination of the elements of interest using appropriate
elemental analysis techniques.
8.4 Method B: Microwave digestion
8.4.1 Method B1: Digestion with HBF , HNO and HCl using microwave heating, temperature-
4 3
controlled, closed vessels
Weigh an amount between 0,2 g to 0,5 g of the dried and pre-treated test portion with an accuracy of
0,001 g and transfer it into the digestion vessel (7.2.1).
The amount of the test sample depends on the amount of organic matter. The maximum amount of organic
carbon shall not exceed 0,15 g when 8 ml of HCl/HNO mixture is used. Per additional 0,1 g organic carbon
(more than this 0,15 g), 1 ml of additional concentrated HNO (6.7) shall be added before the digestion
process is started.
Referring to the manufacturer’s instructions, the upper limits of mass of the test portion shall be taken into
account.
If necessary, moisten the test portion with a few drops of water (6.1). Add (6,0 ± 0,1) ml hydrochloric acid
(6.6) followed by (2,0 ± 0,1) ml nitric acid (6.7) and (4,0 ± 0,1) ml tetrafluoroboric acid (6.2).
If a vigorous reaction occurs, allow the reaction cease before capping the vessel.
Cap the digestion vessel according to the manufacturer’s instructions. Place in all positions of the
microwave oven carrousel (usually 6, 12, 16 or 40 positions) sample vessels. If a lower number of samples
are available compared to the vessel positions, place vessels filled with same amount of the acid mixture
without sample. This is to ensure the same microwave energy absorption occurs during each digestion
procedure. This method is an operationally defined method, designed to achieve consistent digestion of
samples by specific reaction conditions. The temperature of the digestion mixture in each vessel shall be
raised with a heating rate of approximately 10 °C/min to 15 °C/min to (175 ± 5) °C and remain at
(175 ± 5) °C for (10 ± 1) min. Cool down to room temperature.
WARNING — A too high temperature increase may cause a vigorous, exothermic reaction in the digestion
solution with high pressure increase and blow-off of the security valve. Losses of analytes are then possible.
At the end of the microwave oven programme, allow the vessels to cool according to the manufacturer's
instructions before removing them from the microwave system. Cooling of the vessels may be accelerated
by internal or external cooling devices.
After reaching room temperature, check if the microwave vessels maintained their seal throughout the
digestion. Due to the wide variety of vessel designs, a single procedure is not appropriate.
Carefully uncap and vent each vessel in a well-ventilated fume hood according to the manufacturer's
instructions. Transfer quantitatively the solution content of each vessel into a suitable sized volumetric
flask and add water (6.1) to the volume mark.
Alternatively, another procedure can be applied, such that the adjustment to volume with the solid residue
still present shall be carried out immediately after digestion.
If the measurement solution contains suspended particles which may clog nebulizers or interfere with an
injection of the sample into the instrument, the sample may be centrifuged or filtered (7.4).
If the measurement solution contains suspended particles, the digestion is not complete. This should be
stated in the report.
The measurement solution is now ready for the determination of the elements of interest using appropriate
elemental analysis techniques.
8.4.2 Method B2: Digestion with HF, HNO and HCl using microwave heating, power-controlled,
closed vessels
Weigh an amount between 0,2 g to 0,5 g of the dried and pre-treated test portion with an accuracy of
0,001 g and transfer it into the digestion vessel (7.2.1).
The amount of the test sample depends on the amount of organic matter. The maximum amount of organic
carbon shall not exceed 0,15 g when 8 ml of HCl/HNO mixture is used. Per additional 0,1 g organic carbon
(more than this 0,15 g), 1 ml of additional concentrated HNO (6.7) shall be added before the digestion
process is started.
Referring to the manufacturer’s instructions, the upper limits of mass of the test portion shall be taken into
account.
If necessary, moisten the test portion with a few drops of water (6.1). Add (6,0 ± 0,1) ml hydrochloric acid
(6.6) followed by (2,0 ± 0,1) ml nitric acid (6.7) and (2,0 ± 0,1) ml hydrofluoric acid (6.3).
If a vigorous reaction occurs, allow the reaction cease before capping the vessel.
Cap the digestion vessel according to the manufacturer’s instructions. Place in all positions of the
microwave oven carrousel (usually 6, 12, 16 or 40 positions) sample vessels and start the digestion
procedure. The power programme (see Table 2) is intended to be used for batches of 6 samples.
Commercial available microwave units may contain more or less sample positions. In order to ensure
consistant reaction conditions in these cases the power programme shall be adjusted according to the
manufactures instructions. If a lower number of samples are available compared to the vessel positions,
place vessels filled with same amount of the acid mixture without sample. This is to ensure the same
microwave energy absorption occurs during each digestion procedure.
Table 2 — Power programme
Time Power
Min W
2 250
2 0
5 250
5 400
5 500
WARNING — A too high temperature increase may cause a vigorous, exothermic reaction in the digestion
solution with high pressure increase and blow-off of the security valve. Losses of analytes are then possible.
At the end of the microwave programme, allow the vessels to cool according to the manufacturer's
instructions before removing them from the microwave system. Cooling of the vessels may be accelerated
by internal or external cooling devices.
After reaching room temperature, check if the microwave vessels maintained their seal throughout the
digestion. Due to the wide variety of vessel designs, a single procedure is not appropriate.
Carefully uncap and vent each vessel in a well-ventilated fume hood according to the manufacturer's
instructions, then add a solution containing 650 mg of boric acid (e.g. 22 ml of 4 % m/m (6.5)). Cap the
vessels and put them into the microwave unit cavity and start the following programme: 3 min (time) at
300 W (power).
At the end of the microwave programme, allow the vessels to cool according to the manufacturer's
instructions before removing them from the microwave system. Cooling of the vessels may be accelerated
by internal or external cooling devices.
Carefully uncap and vent each vessel in a well-ventilated fume hood according to the manufacturer's
instructions. Transfer quantitatively the solution content of each vessel into a suitable sized volumetric
flask and add water (6.1) to the volume mark.
Alternatively, another procedure can be applied, such that the adjustment to volume with the solid residue
still present shall be carried out immediately after digestion.
If the measurement solution contains suspended particles which may clog nebulizers or interfere with an
injection of the sample into the instrument, the sample may be centrifuged or filtered (7.4).
If the measurement solution contains suspended particles, the digestion is not complete. This should be
stated in the report.
The measurement solution is now ready for the determination of the elements of interest using appropriate
elemental analysis techniques.
9 Test report
This test report shall contain at least the following information:
a) the digestion method used, together with a reference to this document, i.e. EN 13656;
b) identity of the sample;
c) any deviation from this method and report of circumstances that can have affected the results.
Annex A
(normative)
Calibration of the power adjustment
In order to compare the power adjustment of different apparatus among themselves, the actually supplied
(effective) power shall be determined. Also the relationship between the supplied power and the
adjustment scale shall be controlled. Furthermore, the effective power shall be checked periodically.
Calibration is carried out by heating a known amount of water during a fixed time period (e.g. 2 min) at
different microwave power rates. Each raise of temperature has to be measured with a limit deviation
of ± 0,1 °C after each heating cycle. The absorbed power is calculated from the raise of temperature (see
formula at the end of this annex).
Put e.g. 1 kg of water in a plastic beaker (or a beaker made of other material that does not absorb or reflect
microwave energy, glass beaker shall be avoided), stir and measure the temperature. Place the beaker in
the microwave oven. Do always select the same position. Set the microwave during 2 min at full power.
Remove the beaker, stir and measure the final temperature. Repeat this procedure also at lower power
rates.
The power absorbed is calculated with the following formula:
C × m ×∆T
p
P=
t
where
P is the power absorbed by the water in W (J/s);
C is the specific heat for water J/kg °C (= 4184 J/kg °C);
p
m is the mass of the water that is used for the calibration in kg;
ΔT is the difference between initial and final temperature in °C;
t is the time period in s.
If in the described procedure 2 min and 1 kg water are used, the formula can be simplified to:
P = ΔT ×34,87 J/s·°C
where
P is the power absorbed by the water in W (J/s);
ΔT is the difference between initial and final temperature in °C.
Annex B
(informative)
Repeatability and reproducibility data – Method A and B1
B.1 Inter-laboratory study
Between October 2018 and February 2019, a project for validation of method A (Heating block digestion
with HCl, HNO and HBF ) and method B1 (Microwave digestion, temperature-controlled, with HCl, HNO
3 4 3
and HBF ) has been organized and carried out. The validation included an inter-laboratory study for
evaluation of performance characteristics of the method (reproducibility, repeatability, accuracy where
applicable).
B.2 Selection of laboratories
Several CEN/TC444 members were requested to circulate information about the inter-laboratory trial and
collect a list of interested European laboratories. Respectively 9 (for method A) and 8 (for method B1)
laboratories gave their availability to participate to the inter-laboratory trial. All laboratories carried out
the digestion with a heating block and/or microwave at regular basis. The laboratories were informed
about the necessity to carry out digestion and analysis according to this standard. According to the
ISO 5725 series [2] no selection has been made in advance on the basis of the supposed “ability” of
laboratories, their certifications, etc: it's therefore possible to assume that participating laboratories are a
rather good “sample” of “normal” European laboratories.
B.3 Selection of samples
Two samples were taken from the interlaboratory trial for the validation of EN 13656:
— ink waste sludge (organic matrix) (CEN8/99 “INK WASTE CW12 POWDER”);
— electronic industry sludge (“metallic” matrix) (CEN9/99 “SEWAGE SLUDGE SL11 POWDER”).
For accuracy evaluation, two certified reference materials (CRM) have been included:
— ISE 859 (sediment);
— BCR 176R (city waste incineration ash, with identical matrix as BCR 176, used in the inter laboratory
trial for the evaluation of EN 13656).
Additionally, three materials used in robustness validation tests for CEN/TC 351 [14] [15] have been
included:
— CFA Coal fly ash;
— GSS Steel slag;
— CUS Copper slag.
All samples, including the two CRMs, have been delivered to laboratories in anonymous form.
B.4 Experimental
Preparation and homogenization of samples, packaging, delivering, collection and evaluation of results
have been carried out by VITO NV in Mol (Belgium) and Synlab Analytics and Services B.V. in Rotterdam
(The Netherlands) [12] [13].
B.5 Results
All laboratories have actually returned results for the inter-laboratory study. The means and standard
deviations of reproducibility have been evaluated according to ISO 13528:2015, C.1 [9], following these
steps:
— removing of data with a value below the detection limit (“<”-values);
— data have been evaluated if the mean measured concentration is above 1 mg/kg dm (for Hg 0,1 mg/kg
dm);
— data have been evaluated only if more than six results remain;
— for the remaining data sets, means and standard deviations were calculated as Huber-M estimates with
Winsorising at 1.5 standard deviations;
— where a “conventional true value” was available, accuracy (recovery) has been calculated.
The inter-laboratory study involved 9 (method A) and 8 (method B1) laboratories, performing analyses in
two replicates on seven samples, for the determination of a large number of elements (up to 28): this led
to a large data set. For some elements, only few data were available, anyway, even for these elements, useful
information on performance has been obtained.
B.6 Conclusions
The performances of the method should be compared on an element-by-element, matrix-by-matrix basis,
in the tables below. In general, performances are actually well comparable, especially for most
environmentally-sensitive (toxic) elements.
For some elements, e.g. Ba, Sn, Ti, microwave digestion might result in a higher recovery compared to a
heating block digestion.
For the element Ti, a higher recovery might be obtained when using HF instead of HBF (sample
dependent).
Table B.1 — Sample CEN 8/99 “INK WASTE CW12 POWDER”
Method A: Heating block digestion with HCl, HNO and HBF Method B1. Microwave digestion, temperature-controlled, with HCl, HNO and HBF
3 4 3 4
XREF Mean Recovery Reproducibility Repeatability XREF Mean Recovery Reproducibility Repeatability

N L NR N L NR
mg/kg dm mg/kg dm % % % mg/kg dm mg/kg dm % % %
Al 14 7 0 – 2195 – 25,3 5,0 12 6 0 – 2344 – 25,5 15,4
Sb – – – – – – – – – – – – – – – –
As 8 9 10 – 10,3 – 51,3 12,1 9 8 7 – 7,3 – 40,0 6,1
Ba 16 8 0 – 70 – 26,0 7,7 14 7 0 – 92 – 17,3 4,0
Cd – – – – – – – – – – – – – – – –
Ca 14 7 0 – 114971 – 10,3 6,6 14 7 0 – 112376 – 8,4 5,1
Cr 18 9 0 – 3865 – 5,5 3,5 16 8 0 – 3814 – 9,9 5,0
Co 16 8 0 – 16,0 – 6,6 3,5 14 7 0 – 16,3 – 5,1 1,5
Cu 18 9 0 – 13109 – 5,7 4,4 16 8 0 – 12808 – 6,7 4,4
Fe 16 8 0 – 76864 – 4,7 4,3 14 7 0 – 77318 – 8,9 5,0
Pb 18 9 0 – 5805 – 8,2 5,6 16 8 0 – 5791 – 11,1 6,1
Mg 14 7 0 – 1013 – 9,8 1,9 14 7 0 – 938 – 12,6 8,2
Mn 16 8 0 – 581 – 5,0 2,5 14 7 0 – 553 – 15,3 2,8
Hg 18 9 0 – 1,82 – 16,6 3,1 16 8 0 – 1,89 – 29,6 5,9
Mo 10 7 4 – 4,6 – 11,2 3,5 12 6 0 – 4,2 – 27,8 5,2
Ni 18 9 0 – 22 – 6,9 1,9 16 8 0 – 22 – 13,6 3,0
P 16 8 0 – 14017 – 4,9 2,3 14 7 0 – 13632 – 17,3 5,7
K 14 7 0 – 1113 – 14,3 3,1 14 7 0 – 1042 – 25,8 5,4
Ag – – – – – – – – – – – – – – – –
S 16 8 0 – 28508 – 6,7 2,8 14 7 0 – 30209 – 20,8 4,8
Se 8 8 8 – 3,8 – 40,3 14,1 8 7 6 – 3,8 – 10,3 14,5
Na 14 7 0 – 5435 – 6,3 2,1 14 7 0 – 4797 – 32,4 4,2
Sr 16 8 0 – 125 – 12,2 2,8 14 7 0 – 122 – 12,0 1,8
Sn 6 8 10 – 3 – 22,3 10,7 8 7 6 – 4 – 32,1 37,6
Tl – – – – – – – – – – – – – – – –
Ti 16 8 0 – 175 – 4,1 2,2 14 7 0 – 188 – 15,1 5,0
V 16 8 0 – 18 – 8,6 4,3 14 7 0 – 15,9 – 14,6 6,8
Zn 18 9 0 – 1269 – 7,5 2,3 16 8 0 – 1260 – 13,8 3,3
N = Number of results, L = Number of laboratories, NR = Number of results rejected for statistical evaluation, XREF = Conventional true value (where applicable)
Table B.2 — Sample CEN9/99 “SEWAGE SLUDGE SL11 POWDER”
Method A: Heating block digestion with HCl, HNO and HBF Method B1. Microwave digestion, temperature-controlled, with HCl, HNO and HBF
3 4 3 4
XREF Mean Recovery Reproducibility Repeatability XREF Mean Recovery Reproducibility Repeatability
N L NR N L NR
mg/kg dm mg/kg dm % % % mg/kg dm mg/kg dm % % %
Al 14 7 0 – 87073 – 27,6 11,8 12 6 0 – 66795 – 52,7 22,3
Sb 8 8 8 – 5 – 10,1 2,6 8 7 6 – 5 – 6,9 12,4
As 10 9 8 – 5,6 – 34,5 8,8 10 8 6 – 5,5 – 24,9 8,9
Ba 16 8 0 – 74 – 26,8 22,4 14 7 0 – 78 – 21,3 4,5
Cd – – – – – – – – – – – – – – – –
Ca 12 6 0 – 63779 – 11,7 4,8 12 6 0 – 55399 – 23,1 10,1
Cr 18 9 0 – 92 – 5,3 3,2 16 8 0 – 91 – 8,9 3,1
Co 10 9 8 – 6,7 – 19,5 15,8 12 7 2 – 5,8 – 15,0 13,0
Cu 18 9 0 – 104858 – 6,4 3,0 16 8 0 – 103694 – 4,8 3,7
Fe 16 8 0 – 5861 – 11,6 3,2 14 7 0 – 6433 – 12,6 13,2
Pb 18 9 0 – 10126 – 3,4 23,5 16 8 0 – 10245 – 6,4 8,2
Mg 12 6 0 – 2493 – 12,7 9,2 12 6 0 – 1974 – 26,8 17,6
Mn 16 8 0 – 712 – 4,0 1,9 14 7 0 – 713 – 6,2 1,2
Hg 14 9 4 – 0,19 – 22,3 4,7 10 8 6 – 0,21 – 31,0 10,7
Mo 10 7 4 – 5,3 – 6,0 3,1 12 6 0 – 5,3 – 7,9 3,8
NI 18 9 0 – 1967 – 5,4 1,8 16 8 0 – 1993 – 6,6 6,4
P 14 7 0 – 604,9 – 15,2 5,9 12 6 0 – 5823 – 11,3 3,6
K 14 7 0 – 4216 – 29,0 12,4 14 7 0 – 4046 – 37,6 10,5
Ag 14 8 2 – 11,3 – 14,3 25,6 14 7 0 – 10,6 – 15,2 11,7
S 16 8 0 – 70119 – 7,0 3,0 14 7 0 – 70207 – 9,6 4,0
Se – – – – – – – – – – – – – – – –
Na 14 7 0 – 14101 – 16,4 2,8 14 7 0 – 12862 – 19,2 7,2
Sr 16 8 0 – 196 – 20,7 4,6 14 7 0 – 199 – 18,2 3,1
Sn 16 8 0 – 13413 – 10,2 3,7 14 7 0 – 19459 – 14,5 5,5
Tl – – – – – – – – – – – – – – – –
Ti 14 8 2 – 74 – 10,2 2,5 14 7 0 – 87 – 32,9 6,2
V 14 8 2 – 7 – 14,7 5,3 14 7 0 – 6,9 – 13,3 5,8
Zn 18 9 0 – 233 – 6,8 1,3 16 8 0 – 265 – 19,7 1,9
N = Number of results, L = Number of laboratories, NR = Number of results rejected for statistical evaluation, XREF = Conventional true value (where applicable)
Table B.3 — Sample ISE 859 “sediment”
Method A: Heating block digestion with HCl, HNO and HBF Method B1. Microwave digestion, temperature-controlled, with HCl, HNO and HBF
3 4 3 4
XREF Mean Recovery Reproducibility Repeatability XREF Mean Recovery Reproducibility Repeatability
N L NR mg/kg dm mg/kg dm % % % N L NR mg/kg dm m
...