FprEN 13656

SLOVENSKI STANDARD
oSIST prEN 13656:2019
01-oktober-2019

Tla, obdelani biološki odpadki, blato in odpadki - Razklop z zmesjo klorovodikove

kisline (HCl), dušikove(V) kisline (HNO3) in tetrafluoroborove kisline (HBF4) ali

Soil, treated biowaste, sludge and waste - Digestion with a hydrochloric (HCl), nitric

(HNO3) and tetrafluoroboric (HBF4) or hydrofluoric (HF) acid mixture for subsequent

2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

This draft European Standard is submitted to CEN members for enquiry. It has been drawn up by the Technical Committee

If this draft becomes a European Standard, 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.

This draft European Standard was established by CEN 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

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

Recipients of this draft are invited to submit, with their comments, notification of any relevant patent rights of which they are

Warning : This document is not a European Standard. It is distributed for review and comments. It is subject to change without

© 2019 CEN All rights of exploitation in any form and by any means reserved Ref. No. prEN 13656:2019 E

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

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.................................................................................................................................................................. 35

This document (prEN 13656:2019) has been prepared by Technical Committee CEN/TC 444 “Test

methods for environmental testing of solid matrices”, the secretariat of which is held by NEN.

— addition of HBF as acid. For safety reasons the use of HBF is preferred over HF;

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.

Materials used in the validation test Validated for digestion Validated for digestion

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

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

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

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

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

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. For a broad

range of samples the extracted analyte concentrations will reflect the total content in the sample.

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

This document can also be applied for the digestion of other elements, provided the user has verified the

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

ISO and IEC maintain terminological databases for use in standardization at the following addresses:

mineralization of the organic matter of a sample and dissolution of its mineral part, more or less

dry matter expressed as a percentage by mass after drying at 105 °C ± 5 °C to the constancy of weight

quantity of material, of proper size for measurement of the concentration or other property of interest,

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,

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

— A: Digestion with HCl, HNO and HBF using a heating block at (105 ± 5) °C for 2 h, followed by

— B1: Digestion with HCl, HNO and HBF using a microwave with temperature-controlled

— B2: Digestion with HCl, HNO and HF using a microwave with power-controlled procedure in a

NOTE Alternatively, microwave digestion with temperature-controlled procedure in a closed vessel can be

Due to safety considerations, the digestion with HCl, HNO and HBF is strongly recommended over the

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,

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

For the determination of elements forming volatile elements/compounds (e. g. Hg, As, Pb), special care

In the case of filtration of the digested solution, it is necessary to take care that the filtration procedure

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

The upper limits of mass of the test portion according to the manufacturer's specifications have to be

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

Use only acids and reagents of recognized analytical grade to avoid high blank values for subsequent

analytical measurements. Use a test blank solution throughout the procedure applying all steps with the

Usual laboratory apparatus. All glassware and plastics ware shall be adequately cleaned and stored in

Depending on the concentration of the element of interest, particular caution shall be taken with respect

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

7.1.2 Temperature-controlled heating block, heating block able to heat the tube(s) to a temperature

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,

Digestion vessels made of modified polytetrafluoroethene (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

NOTE It can be necessary to periodically clean the digestion vessels with a suitable surfactant to remove

7.2.2 Microwave digestion system, temperature-controlled, corrosion resistant and well ventilated.

Use a laboratory-grade microwave oven with temperature feedback control mechanisms.

The microwave digestion system should be able to control the temperature with an accuracy of ± 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

The accuracy of the temperature measurement system should 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

7.2.3 Microwave digestion system, power-controlled, corrosion resistant and well ventilated. All

The microwave unit should 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 has to be performed (see

The microwave unit shall be designed in a way that guarantees homogeneous heating of the samples.

The microwave unit cavity has to 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.

7.4 Filter, usually with a pore size of 0,45 µm and resistant to the employed acid mixture.

Pre-treat, if not otherwise specified, soil, sludge and biowaste samples according to EN 16179 and waste

Determine the dry matter content, depending on the matrix of the sample, according to EN 15934.

Pre-treatment should include drying or grain size reduction below a particle size of 250 µm or

The mass of test portion for a single digestion has to be selected in a way that:

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

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

NOTE The measurement of a blank is introduced to determine the contribution of the extracting solution,

Weigh approximately 0,2 g to 0,5 g of the dried and pre-treated test portion with an accuracy of 0,001 g

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 and HNO 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

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

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).

The measurement solution is now ready for the determination of the elements of interest using

8.4.1 Method B1: Digestion with HBF , HNO and HCl using microwave heating, temperature-

Weigh an amount between 0,2 g to 0,5 g of the dried and pre-treated test portion with an accuracy of

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 and HNO 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

Referring to the manufacturer’s instructions, the upper limits of mass of the test portion shall be taken

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 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

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

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

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

Alternatively, another procedure can be applied, such that the adjustment to volume with the solid

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).

The measurement solution is now ready for the determination of the elements of interest using

8.4.2 Method B2: Digestion with HF, HNO and HCl using microwave heating, power-controlled,

Weigh an amount between 0,2 g to 0,5 g of the dried and pre-treated test portion with an accuracy of

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 and HNO is used. Per additional 0,1 g organic

carbon (more than this 0,15 g), 1 ml of additional concentrated HNO3 (6.7) shall be added before the

Referring to the manufacturer’s instructions, the upper limits of mass of the test portion shall be taken

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 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 has to 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

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