Soil, waste, treated biowaste and sludge - Determination of total organic carbon (TOC) by dry combustion

This European Standard specifies two methods for the determination of total organic carbon (TOC) in sludge, treated biowaste, soil, waste and sediment samples containing more than 1 g carbon per kg of dry matter (0,1 %).
When present, elementary carbon, carbides, cyanides, cyanates, isocyanates, isothiocyanates and thio-cyanates are determined as organic carbon using the methods described in this European Standard. An interpretation of the measured value may therefore be problematic in cases where the samples contain relevant levels of the above mentioned components. If necessary, these components should be determined separately by means of a suitable validated procedure and be recorded in the test report.
For sludge, treated biowaste and soil only Method A is validated.

Boden, Abfall, behandelter Bioabfall und Schlamm - Bestimmung des gesamten organischen Kohlenstoffs (TOC) mittels trockener Verbrennung

Dieses Dokument legt zwei Verfahren zur Bestimmung des gesamten organischen Kohlenstoffs (TOC) in Schlamm, behandeltem Bioabfall, Boden, und Abfallproben fest, die mehr als 0,1 % Kohlenstoff bezogen auf die Trockenmasse (dm) enthalten.
ANMERKUNG   Dieses Verfahren kann auch auf andere feste Umweltmatrizen angewandt werden, sofern der Anwender die Anwendbarkeit überprüft hat.

Sols, déchets, biodéchets traités et boues - Dosage du carbone organique total (COT) par combustion sèche

Le présent document spécifie deux méthodes de dosage du carbone organique total (COT) dans des échantillons de boues, de biodéchets traités, de sols et de déchets contenant plus de 0,1 % de carbone par rapport à la masse sèche (ms).
NOTE   Cette méthode peut également être appliquée à d’autres matrices solides environnementales, à condition que l’utilisateur ait vérifié son applicabilité.

Tla, odpadki, obdelani biološki odpadki in blato - Določevanje celotnega organskega ogljika (TOC) s suhim sežigom

General Information

Status
Published
Public Enquiry End Date
01-Aug-2020
Publication Date
15-Jun-2022
Technical Committee
Current Stage
6060 - National Implementation/Publication (Adopted Project)
Start Date
21-Apr-2022
Due Date
26-Jun-2022
Completion Date
16-Jun-2022

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Standards Content (sample)

SLOVENSKI STANDARD
SIST EN 15936:2022
01-julij-2022
Nadomešča:
SIST EN 15936:2012
Tla, odpadki, obdelani biološki odpadki in blato - Določevanje celotnega
organskega ogljika (TOC) s suhim sežigom

Soil, waste, treated biowaste and sludge - Determination of total organic carbon (TOC)

by dry combustion
Boden, Abfall, behandelter Bioabfall und Schlamm - Bestimmung des gesamten
organischen Kohlenstoffs (TOC) mittels trockener Verbrennung

Sols, déchets, biodéchets traités et boues - Dosage du carbone organique total (COT)

par combustion sèche
Ta slovenski standard je istoveten z: EN 15936:2022
ICS:
13.030.20 Tekoči odpadki. Blato Liquid wastes. Sludge
13.080.10 Kemijske značilnosti tal Chemical characteristics of
soils
SIST EN 15936:2022 en,fr,de

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

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SIST EN 15936:2022
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SIST EN 15936:2022
EN 15936
EUROPEAN STANDARD
NORME EUROPÉENNE
February 2022
EUROPÄISCHE NORM
ICS 13.030.01; 13.080.10 Supersedes EN 15936:2012
English Version
Soil, waste, treated biowaste and sludge - Determination of
total organic carbon (TOC) by dry combustion

Sols, déchets, biodéchets traités et boues - Dosage du Boden, Abfall, behandelter Bioabfall und Schlamm -

carbone organique total (COT) par combustion sèche Bestimmung des gesamten organischen Kohlenstoffs

(TOC) mittels trockener Verbrennung
This European Standard was approved by CEN on 19 December 2021.

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 NORMALISATION
EUROPÄISCHES KOMITEE FÜR NORMUNG
CEN-CENELEC Management Centre: Rue de la Science 23, B-1040 Brussels

© 2022 CEN All rights of exploitation in any form and by any means reserved Ref. No. EN 15936:2022 E

worldwide for CEN national Members.
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SIST EN 15936:2022
EN 15936:2022 (E)
Contents Page

European foreword ....................................................................................................................................................... 4

Introduction .................................................................................................................................................................... 5

1 Scope .................................................................................................................................................................... 6

2 Normative references .................................................................................................................................... 6

3 Terms and definitions ................................................................................................................................... 6

4 Principle ............................................................................................................................................................. 6

4.1 Method A (indirect procedure) .................................................................................................................. 6

4.2 Method B (direct procedure) ...................................................................................................................... 7

5 Interferences .................................................................................................................................................... 7

6 Reagents ............................................................................................................................................................. 7

7 Apparatus ........................................................................................................................................................... 8

8 Sample pre-treatment ................................................................................................................................... 8

9 Procedure – Method A (indirect method) .............................................................................................. 9

9.1 Determination .................................................................................................................................................. 9

9.1.1 General ................................................................................................................................................................ 9

9.1.2 Determination of the TC ............................................................................................................................... 9

9.1.3 Determination of the TIC .............................................................................................................................. 9

9.2 Calibration ...................................................................................................................................................... 10

9.3 Control measurements ............................................................................................................................... 10

9.4 Calculation and expression of results ................................................................................................... 11

10 Procedure Method B (direct method) ................................................................................................... 12

10.1 Determination ............................................................................................................................................... 12

10.1.1 General ............................................................................................................................................................. 12

10.1.2 Removal of the inorganic carbon and determination of the TOC ............................................... 12

10.2 Calibration ...................................................................................................................................................... 12

10.3 Control measurements ............................................................................................................................... 13

10.4 Calculation and expression of results ................................................................................................... 13

11 Performance data ......................................................................................................................................... 14

12 Expression of results ................................................................................................................................... 14

13 Test report ...................................................................................................................................................... 14

Annex A (informative) Repeatability and reproducibility data ............................................................... 15

A.1 Materials used in the interlaboratory comparison study ............................................................. 15

A.2 Interlaboratory results .............................................................................................................................. 16

Annex B (informative) Factors influencing dry combustion methods ................................................... 19

B.1 Influence of temperature and modifiers on the decomposition of barium carbonate

as an example for a refractory compound .......................................................................................... 19

B.2 Recovery of the control mixture A ......................................................................................................... 19

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SIST EN 15936:2022
EN 15936:2022 (E)

B.3 Influence of aluminium oxide or sodium sulfate used for sample preparation for the

recovery of TOC ............................................................................................................................................. 20

B.4 Influence of TIC:TOC ratio on the recovery and the coefficient of variation ........................... 21

B.5 Method B: Influence of the temperature during the removal of inorganic carbon on

the recovery of TOC ...................................................................................................................................... 22

Bibliography ................................................................................................................................................................. 23

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SIST EN 15936:2022
EN 15936:2022 (E)
European foreword

This document (EN 15936:2022) has been prepared by Technical Committee CEN/TC 444

“Environmental characterization of solid matrices”, the secretariat of which 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 August 2022, and conflicting national standards shall be

withdrawn at the latest by month August 2022.

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 15936:2012.
This document combines methods from EN 15936:2012 and EN 13137:2001.
The main changes compared to the previous edition are as follows:

— New composition of the substances in control mixture A (6.10) was defined and the recovery

requirement (9.3) was adapted to the results of a lab trial;

— Annex C – “Determination of total organic carbon (TOC) in solid samples using the suspension

method” was skipped;
— The text was editorially revised.

Any feedback and questions on this document should be directed to the users’ national standards body.

A complete listing of these bodies can be found on the CEN website.

According to the CEN-CENELEC Internal Regulations, the national standards organisations 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.
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SIST EN 15936:2022
EN 15936:2022 (E)
Introduction

This document is applicable and validated for several types of matrices as indicated in Table 1 (see also

Annex A for the results of the validation). The results in this document are expressed in % C in relation

to the dry mass (dm).
Table 1 — Matrices for which this document is applicable and validated
Matrix Materials used for validation
Sludge Municipal sludge
Biowaste Compost,
Fresh Compost
Soil Sludge amended soil,
Agricultural soil
Waste Filter cake,
Bottom ash,
Electro-plating sludge,
Dredged sludge,
Rubble

WARNING — Persons using this document should be familiar with usual laboratory practice. This

document does not purport to address all of the safety problems, if any, associated with its use. It is the

responsibility of the user to establish appropriate safety and health practices.

IMPORTANT — It is absolutely essential that tests conducted according to this document be carried out

by suitably trained staff.
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SIST EN 15936:2022
EN 15936:2022 (E)
1 Scope

This document specifies two methods for the determination of total organic carbon (TOC) in sludge,

treated biowaste, soil and waste samples containing more than 0,1 % carbon in relation to the dry mass

(dm).

NOTE This method can also be applied to other environmental solid matrices, provided the user has verified

the applicability.
2 Normative references
There are no normative references in this document.
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.

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

— ISO Online browsing platform: available at https://www.iso.org/obp/
— IEC Electropedia: available at https://www.electropedia.org/
3.1
total carbon

quantity of carbon present in the sample in the form of organic, inorganic and elemental carbon

3.2
total inorganic carbon
TIC
quantity of carbon that is liberated as carbon dioxide by acid treatment

Note 1 to entry: Typically, the TIC represents the carbonates present in a sample.

3.3
total organic carbon
TOC

quantity of carbon that is converted into carbon dioxide by combustion and which is not liberated as

carbon dioxide by acid treatment
4 Principle
4.1 Method A (indirect procedure)

In this procedure, the TOC is obtained by the difference between the results of the measurements of TC

and TIC.

The total carbon (TC) present in the sample is converted into carbon dioxide by combustion in an oxygen-

containing gas flow free of carbon dioxide. To ensure complete combustion, catalysts and/or modifiers

can be used. The released amount of carbon dioxide is measured e.g. by infrared spectrometry, thermal

conductivity detection, or other suitable techniques.

The TIC is determined separately from another sub-sample by means of acidification and purging of the

released carbon dioxide. The carbon dioxide shall be measured by one of the techniques mentioned

above.
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SIST EN 15936:2022
EN 15936:2022 (E)
4.2 Method B (direct procedure)

In this procedure, the TIC present in the sample are previously removed by treating the sample with acid.

The carbon dioxide released by the following combustion step is measured by one of the techniques

mentioned in 4.1 and indicates the TOC directly.

NOTE The quality of results of Method B is dependent on experience and practice, especially regarding the

steps before the determination of TOC. Use of automatic dispensing units regarding removal of TIC prior to

determination of TOC can improve the performance of Method B.
5 Interferences

Depending on the laboratory experience with samples containing high amounts of TIC, the procedures

can lead to unreliable TOC results if the TIC to TOC ratio is very high (e.g. ≥ 10).

Depending on the detection method used, different interferences can occur, for instance:

— the presence of cyanide can interfere with the coulometric detection of TIC by modifying the pH value

(dissolution of HCN);

— high content of halogenated compounds can lead to an overestimation of TOC when coulometric

detection is used; in some cases the classical silver or copper trap can be insufficient to absorb all

halides.
Method B can lead to incorrect results in the following cases:

— Volatile organic substances (e.g. volatile hydrocarbons from sludge of oil separators) can be lost

during sample preparation especially during the acidification. If necessary, the carbon content

resulting from volatile organic substances shall be determined separately.

— side reactions between the sample and the acid take place (e.g. decarboxylation, volatile reaction

products).

When present, elemental carbon, carbides, cyanides, cyanates, isocyanates, isothiocyanates and

thiocyanates are determined as organic carbon using the methods described in this document. An

interpretation of the measured value can therefore be problematic in cases where the sample contains

relevant levels of the above-mentioned components. If needed, these components shall be determined

separately by means of a suitable validated method and be recorded in the test report.

6 Reagents
Use only reagents of recognized analytical grade, unless otherwise specified.
Hygroscopic substances shall be stored in a desiccator.
6.1 Calcium carbonate, CaCO .
6.2 Sodium carbonate, Na CO , anhydrous.
2 3
6.3 Tetrasodium ethylenediamine tetraacetate-tetra-hydrate, Na -EDTA ∙ 4 H O
4 2
(C H N O Na ∙ 4 H O), heated at 80 °C for 2 h.
10 12 2 8 4 2

Other forms of Na -EDTA hydrates may be used if the water content is exactly known. In these cases, the

composition of the control mixtures shall be recalculated accordingly (see also 6.10 and 6.11).

6.4 Potassium hydrogen phthalate, C H O K.
8 5 4
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SIST EN 15936:2022
EN 15936:2022 (E)
6.5 Acetanilide, C H NO.
8 9
6.6 Atropine, C H NO .
17 23 3
6.7 Spectrographic graphite powder, C.
6.8 Sodium salicylate, C H O Na.
7 5 3
6.9 Aluminium oxide, Al O , neutral, granular size < 200 µm, annealed at 600 °C.
2 3

6.10 Control mixture A, prepared from sodium carbonate (6.2), Na -EDTA ∙ 4 H O (6.3) and aluminium

4 2
oxide (6.9) in a mass ratio of 2,34 : 1,00 : 7,28.

The mixture shall be homogenized. It shall contain 2,5 % TIC and 2,5 % TOC (e.g. 22,06 g of sodium

carbonate, 9,41 g Na -EDTA ∙ 4 H O, 68,53 g of aluminium oxide).
4 2

6.11 Control mixture B, prepared from sodium salicylate (6.8), calcium carbonate (6.1), Na -EDTA ·

4 H O (6.3) and aluminium oxide (6.9) in a mass ratio of 1,00 : 4,36 : 1,97 : 8,39.

The mixture shall be homogenized. It shall contain 3,3 % TIC and 6,6 % TOC (e.g. 6,36 g of sodium

salicylate, 27,78 g of calcium carbonate, 12,50 g of Na -EDTA · 4 H O, 53,36 g of aluminium oxide).

4 2

6.12 Non-oxidizing mineral acid, used for carbon dioxide expulsion, e.g. phosphoric acid H PO

3 4
(w = 85 %).

NOTE Due to potential corrosion by hydrochloric acid, phosphoric acid is preferred for TIC determination in

Method A (9.1.3). Due to potential formation of P O during combustion, hydrochloric acid is preferred for removal

4 10
of inorganic carbon in Method B (10.1.2).

6.13 Carrier gas, e.g. synthetic air, nitrogen, oxygen or argon, free of carbon dioxide and organic

impurities in accordance with the manufacturer's instructions.
7 Apparatus
7.1 Precision balance, accurate to at least 0,5 % of test portion weight.
7.2 Equipment for determination of carbon in solids, with relevant accessories.
7.3 Purging unit for TIC determination, for Method A only.
7.4 Vessels, made of e.g. ceramic, silica, quartz, silver or platinum.

NOTE Tin and nickel vessels are not acid-resistant. Tin vessels are suitable only for Method A.

8 Sample pre-treatment

The sample should be pre-treated according to EN 16179 or EN 15002, if not otherwise specified. The

particle size shall be < 250 μm. Foreign bodies or non-comminutable material should be separated from

the sample and the weight and nature of the material should be recorded.
For solid materials, dried samples shall be used.
NOTE 1 The drying method can affect the result.
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SIST EN 15936:2022
EN 15936:2022 (E)

Moist or paste-like waste samples may be mixed with aluminium oxide (6.9) until granular material is

obtained and then be comminuted to a particle size < 250 μm. In this case, the ratio of aluminium oxide

to sample shall be considered in the calculation of TOC (according to 9.4 or 10.4).

If samples contain – depending on the accuracy requested for the method – negligible amounts of volatile

compounds except water, the samples shall be dried.

NOTE 2 For waste samples, the homogeneity is important and often the aluminium oxide step is helpful. More

information is given in Annex B.
9 Procedure – Method A (indirect method)
9.1 Determination
9.1.1 General

The mass of the test portion shall be as large as possible and shall be chosen so that the liberated quantity

of carbon dioxide lies within the working range of the equipment/calibration.
9.1.2 Determination of the TC

To minimize carbon blank values the vessel may be pre-treated by heating (in a muffle furnace or the TC

apparatus itself). The sample prepared according to Clause 8 is weighed into a suitable vessel (7.4).

The sample is combusted or decomposed in a flow of carrier gas containing oxygen (6.13).

The combustion temperature shall be high enough to convert all carbon completely to carbon dioxide.

NOTE For samples containing carbonates, which are difficult to decompose, e.g. barium carbonate, the release

of the carbon dioxide can be improved by increasing the temperature or by the use of modifiers, e.g. tin, copper (see

B.1).

The temperature range of commercially available instruments is between 900 °C and 1 500 °C.

During the combustion of reactive samples, explosion or fuming can be prevented by covering the sample

with inert material e.g. silica sand.

The amount of carbon dioxide released during the combustion is measured e.g. by infrared spectrometry,

thermal conductivity detection, or other suitable techniques, and is expressed as total carbon (TC).

9.1.3 Determination of the TIC

The sample prepared according to Clause 8 is weighed into the purging unit (7.3) or in the sample vessel

(7.4).

The system is closed gas-tight and flushed with carrier gas until no more carbon dioxide from ambient

air is present. Then acid (6.12) is added and the carbon dioxide is stripped by purging or stirring and/or

heating. The released carbon dioxide is transferred to the detector by the carrier gas.

The addition of wetting agents, e.g. surfactants, can improve wetting of the surface of the sample.

The addition of anti-foaming agents, e.g. silicone oil, can be helpful in the case of strongly foaming

samples.

The amount of carbon dioxide released during the gas evolution is measured e.g. by infrared

spectrometry, thermal conductivity detection, or other suitable techniques and is expressed as total

inorganic carbon (TIC).

Samples containing persistent carbonates (e.g. concrete, cement) require treatment with hot acid for

complete release of carbon dioxide according to manufacturers' instructions.
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SIST EN 15936:2022
EN 15936:2022 (E)
9.2 Calibration

If a relative method is used for detection, e.g. infrared detection, calibration is necessary.

Calibration is to be performed according to the manufacturer's instruction.

Examples of calibration substances suitable for TC are calcium carbonate (6.1), potassium hydrogen

phthalate (6.4), acetanilide (6.5), atropine (6.6), spectrographic graphite powder (6.7).

The following procedure shall be applied for calibration:
— Establish the preliminary working range.

— Measure a minimum of five standard samples. Typically, different sample weights of one calibration

substance are used to cover the calibration range. The absolute amount of carbon of these standard

samples shall be distributed evenly over the working range.

— Carry out a linear regression analysis and test the linearity of the calibration function (e.g.

ISO 8466-1).

— Use the calibration function for calculating the mean values of the recovery of each standard sample.

The function shall be linear. Otherwise, the working range shall be restricted to the linear range.

If an absolute method is used for detection, e.g. coulometry, only control measurements according to 9.3

shall be carried out.

This calibration shall be carried out for initial validation purposes or after major changes of the

equipment.
9.3 Control measurements

Control measurements shall be carried out using control mixture A (6.10) for the procedures according

to 9.1.2 (TC) and 9.1.3 (TIC). Analysis of one concentration from the middle of the respective working

range, possibly repeated two or three times, is sufficient. For the TC and TIC the mean recovery shall be

between 80 % and 120 % with a coefficient of variation ≤ 5 %.
Blank values shall be taken into account, if necessary.

If the required recoveries are not achieved, the following measures can be helpful.

For TC analysis:
— checking the homogeneity of the control mixture;
— checking the calibration;
— increasing the temperature during release of carbon dioxide;
— reducing the flow of the carrier gas;
— encouraging a turbulent flow in the combustion tube;
— use of modifiers;
— use of catalysts for post-oxidation of combustion gases.
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SIST EN 15936:2022
EN 15936:2022 (E)
For TIC analysis:
— optimizing the stirring speed and/or the gas flow in the purging vessel;
— improving the gas exchange in the purging vessel;
— avoiding condensation in the system.
9.4 Calculation and expression of results
The TC and TIC mass contents are calculated from:
— calibration function and sample mass if relative detection methods are used;
— specific constants and sample mass if absolute detection methods are used.

The calculation of TOC is achieved from the difference of the mean values of TC and TIC according to

Formula (1):
m Fm− m (1)
( )
TOC TC TIC

In case of mixing the sample with aluminium oxide (see Clause 8) a dilution factor following Formula (2)

shall be used:
m + m
F= (2)
where

is the TOC content as carbon in the sample expressed in % C in relation to the dry mass (dm);

TOC

m is the mean value of the TC content as carbon in the sample, prepared according to Clause 8

expressed in % C in relation to the dry mass (dm);

is the mean value of the TIC content as carbon in the sample prepared according to Clause 8

TIC
expressed in in % C in relation to the dry mass (dm);

is the dilution factor resulting from the sample preparation of the sample according to

Clause 8;
is the mass of the sample expressed in grams (g);
is the mass of aluminium oxide expressed in grams (g).

The TOC value resulting from Formula (1) is calculated on dry matter basis by Formula (3). For this

purpose, the water content, determined separately according to e.g. EN 15934 or ISO 11465, is used:

100
m m× (3)
TOC, dm TOC
100− w
where

is the TOC content as carbon, calculated on dry matter basis expressed in % C in relation to

TOC, dm
the dry mass (dm);
is the TOC content as carbon in the sample expressed in % C;
TOC
is the water content of the sample as mass fraction expressed in percent (%).
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SIST EN 15936:2022
EN 15936:2022 (E)

The TOC content is reported as carbon on a dry matter basis. According to Formula (3) results are

obtained in in % C, but other units may be used.

For waste and sludge samples TC and TIC shall be measured at least twice. The respective difference of

the two values shall be ≤ 10 % of the mean. If this is not the case, at least one further determination is

necessary; then the coefficient of variation shall be ≤ 10 %. If this is not the case, the relevant coefficient

of variation shall be reported together with the result or all results of the different determination shall

be reported.
10 Procedure Method B (direct method)
10.1 Determination
10.1.1 General

The mass of the test portion shall be as large as possible and shall be chosen so that the liberated quantity

of carbon dioxide lies within the working range of the equipment/calibration.
10.1.2 Removal of the inorganic carbon and determination of the TOC

The sample prepared according to Clause 8 is weighed into a suitable vessel (7.4). The vessel may be

prepared by suitable thermal treatment (in a muffle furnace or the combustion apparatus itself) to

minimize carbon blank values.

In order to remove the inorganic carbon prior to the determination of TOC, the sample is carefully treated

with a small volume of non-oxidizing mineral acid (6.12). Add the acid slowly (dropwise) to avoid

foaming and splashing of the sample. Add as little acid as possible but enough to soak the entire sample

and to remove the inorganic carbon completely.

Allow at least 4 h for the complete removal of the carbon dioxide. Mixing the sample can reduce time

needed for decomposition.

If moistening with the acid is difficult, the sample may be dampened beforehand with as little water as

possible.

The moisture may be partly removed before combustion. The temperature during this sample treatment

is not allowed to exceed 40 °C.
Combust the sample in the carrier gas containing oxygen (6.13).

The combustion temperature shall be high enough to convert the organic carbon completely to carbon

dioxide. The use of modifiers, e.g. tin, copper can increase the recovery.

The temperature range of commercially available instruments is between 900 °C and 1 500 °C.

During the combustion of reactive samples, explosion or fuming can be prevented by covering the sample

with inert material e.g. silica sand after removal of
...

SLOVENSKI STANDARD
oSIST prEN 15936:2020
01-julij-2020
Blato, obdelani biološki odpadki, tla in odpadki - Določevanje celotnega
organskega ogljika (TOC) s suhim sežigom

Sludge, treated biowaste, soil and waste - Determination of total organic carbon (TOC)

by dry combustion
Schlamm, behandelter Bioabfall, Boden und Abfall - Bestimmung des gesamten
organischen Kohlenstoffs (TOC) mittels trockener Verbrennung

Boues, bio-déchets traités, sols et déchets - Détermination de la teneur en carbone

organique total (COT) par combustion sèche
Ta slovenski standard je istoveten z: prEN 15936
ICS:
13.030.20 Tekoči odpadki. Blato Liquid wastes. Sludge
13.080.10 Kemijske značilnosti tal Chemical characteristics of
soils
oSIST prEN 15936:2020 en,fr,de

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

---------------------- Page: 1 ----------------------
oSIST prEN 15936:2020
---------------------- Page: 2 ----------------------
oSIST prEN 15936:2020
DRAFT
EUROPEAN STANDARD
prEN 15936
NORME EUROPÉENNE
EUROPÄISCHE NORM
June 2020
ICS 13.030.01; 13.080.10 Will supersede EN 15936:2012
English Version
Sludge, treated biowaste, soil and waste - Determination of
total organic carbon (TOC) by dry combustion

Boues, bio-déchets traités, sols et déchets - Schlamm, behandelter Bioabfall, Boden und Abfall -

Détermination de la teneur en carbone organique total Bestimmung des gesamten organischen Kohlenstoffs

(COT) par combustion sèche (TOC) mittels trockener Verbrennung

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

CEN/TC 444.

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

Management Centre has the same status as the official versions.

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United Kingdom.

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

aware and to provide supporting documentation.

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

notice and shall not be referred to as a European Standard.
EUROPEAN COMMITTEE FOR STANDARDIZATION
COMITÉ EUROPÉEN DE NORMALISATION
EUROPÄISCHES KOMITEE FÜR NORMUNG
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. prEN 15936:2020 E

worldwide for CEN national Members.
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Contents Page

European foreword ....................................................................................................................................................... 4

Introduction .................................................................................................................................................................... 5

1 Scope .................................................................................................................................................................... 6

2 Normative references .................................................................................................................................... 6

3 Terms and definitions ................................................................................................................................... 6

4 Principle ............................................................................................................................................................. 6

4.1 Method A (indirect procedure) .................................................................................................................. 6

4.2 Method B (direct procedure) ...................................................................................................................... 7

4.3 Applicability of Methods A or B .................................................................................................................. 7

5 Interferences .................................................................................................................................................... 7

6 Reagents ............................................................................................................................................................. 8

6.2 Sodium carbonate, Na2CO3, anhydrous. .................................................................................................. 8

-EDTA ∙ 4 H O
6.3 Tetrasodium ethylenediamine tetraacetate-tetra-hydrate, Na4 2

(C H N O Na ∙ 4 H O), heated at 80 °C for 2 h. .................................................................................. 8

10 12 2 8 4 2

6.4 Potassium hydrogen phthalate, C H O K. ............................................................................................... 8

8 5 4

6.5 Acetanilide, C H NO. ....................................................................................................................................... 8

8 9

6.6 Atropine, C H NO . ....................................................................................................................................... 8

17 23 3

6.7 Spectrographic graphite powder, C. ......................................................................................................... 8

6.8 Sodium salicylate, C H O Na........................................................................................................................ 8

7 5 3

6.9 Aluminium oxide, Al O , neutral, granular size < 200 µm, annealed at 600 °C. ....................... 8

2 3

6.10 Control mixture A, prepared from sodium carbonate (6.2), Na -EDTA ∙ 4 H O (6.3)

4 2

and aluminium oxide (6.9) in a mass ratio of 2,34 : 1,00 : 7,28. ..................................................... 8

6.11 Control mixture B, prepared from sodium salicylate (6.8), calcium carbonate (6.1),

Na4-EDTA · 4 H O (6.3) and aluminium oxide (6.9) in a mass ratio of

1,00 : 4,36 : 1,97 : 8,40. .................................................................................................................................. 8

6.12 Non-oxidizing mineral acid, used for carbon dioxide expulsion, e.g. phosphoric acid

H PO (w = 85 %). .......................................................................................................................................... 8

3 4

6.13 Carrier gas, e.g. synthetic air, nitrogen, oxygen or argon, free of carbon dioxide and

organic impurities in accordance with the manufacturer's instructions. .................................. 8

7 Apparatus ........................................................................................................................................................... 9

7.1 Precision balance, accurate to at least 0,5 % of test portion weight. ........................................... 9

7.2 Equipment for determination of carbon in solids, with relevant accessories. ......................... 9

7.3 Purging unit for TIC determination, for Method A only. ................................................................... 9

7.4 Vessels, made of e.g. ceramic, silica, quartz, silver or platinum..................................................... 9

8 Sample pre-treatment ................................................................................................................................... 9

9 Procedure – Method A (indirect method) .............................................................................................. 9

9.1 Determination .................................................................................................................................................. 9

9.1.1 General ................................................................................................................................................................ 9

9.1.2 Determination of the TC ............................................................................................................................... 9

9.1.3 Determination of the TIC ........................................................................................................................... 10

9.2 Calibration ...................................................................................................................................................... 10

9.3 Control measurements ............................................................................................................................... 11

9.4 Calculation and expression of results ................................................................................................... 11

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10 Procedure Method B (direct method) ................................................................................................... 12

10.1 Determination................................................................................................................................................ 12

10.1.1 General ............................................................................................................................................................. 12

10.1.2 Removal of the inorganic carbon and determination of the TOC ................................................ 13

10.2 Calibration ....................................................................................................................................................... 13

10.3 Control measurements ............................................................................................................................... 13

10.4 Calculation and expression of results ................................................................................................... 14

11 Performance data ......................................................................................................................................... 14

12 Expression of results ................................................................................................................................... 15

13 Test report ...................................................................................................................................................... 15

Annex A (informative) Repeatability and reproducibility data ................................................................ 16

A.1 Materials used in the interlaboratory comparison study .............................................................. 16

A.2 Interlaboratory results ............................................................................................................................... 17

Annex B (informative) Factors influencing dry combustion methods ................................................... 19

B.1 Influence of temperature and modifiers on the decomposition of barium carbonate

as an example for a refractory compound ........................................................................................... 19

B.2 Recovery of the control mixture A .......................................................................................................... 19

B.3 Influence of aluminium oxide or sodium sulfate used for sample preparation for the

recovery of TOC ............................................................................................................................................. 20

B.4 Influence of TIC:TOC ratio on the recovery and the coefficient of variation ........................... 21

B.5 Method B: Influence of the temperature during the removal of inorganic carbon on

the recovery of TOC ...................................................................................................................................... 22

Bibliography ................................................................................................................................................................. 23

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European foreword

This document (prEN 15936:2020) has been prepared by Technical Committee CEN/TC 444

“Environmental characterization of solid matrices”, the secretariat of which is held by NEN.

This document is currently submitted to the CEN Enquiry.
This document will supersede EN 15936:2012.
This document combines methods from EN 15936:2012 and EN 13137:2001.
The main changes compared to the previous edition are as follows:

— New composition of the substances in control mixture A [6.10] was defined and the recovery

requirement [9.3] was adapted to the results of a lab trial.

— Annex C – “Determination of total organic carbon (TOC) in solid samples using the suspension

method” was skipped.
— The text was editorially revised.
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Introduction

This document is applicable and validated for several types of matrices as indicated in Table 1 (see also

Annex A for the results of the validation).
Table 1 — Matrices for which this document is applicable and validated
Matrix Materials used for validation
Sludge Municipal sludge
Biowaste Compost,
Fresh Compost
Soil Sludge amended soil,
Agricultural soil
Waste Filter cake,
Bottom ash,
Electro-plating sludge,
Dredged sludge,
Rubble

WARNING — Persons using this document should be familiar with usual laboratory practice. This

document does not purport to address all of the safety problems, if any, associated with its use. It is the

responsibility of the user to establish appropriate safety and health practices and to ensure compliance

with any national regulatory conditions.

IMPORTANT — It is absolutely essential that tests conducted according to this document be carried

out by suitably trained staff.
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1 Scope

This document specifies two methods for the determination of total organic carbon (TOC) in sludge,

treated biowaste, soil, waste and sediment samples containing more than 1 g carbon per kg of dry

matter (0,1 %).
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:

— ISO Online browsing platform: available at https://www.iso.org/obp/ui
— IEC Electropedia: available at http://www.electropedia.org/
3.1
total carbon

quantity of carbon present in the sample in the form of organic, inorganic and elemental carbon

3.2
total inorganic carbon
TIC

quantity of carbon that is liberated as carbon dioxide by acid treatment. Typically, the TIC represents

the carbonates present in a sample
3.3
total organic carbon
TOC

quantity of carbon that is converted into carbon dioxide by combustion and which is not liberated as

carbon dioxide by acid treatment
4 Principle
4.1 Method A (indirect procedure)

In this procedure, the TOC is obtained by the difference between the results of the measurements of TC

and TIC.

The total carbon (TC) present in the sample is converted into carbon dioxide by combustion in an

oxygen-containing gas flow free of carbon dioxide. To ensure complete combustion, catalysts and/or

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modifiers can be used. The released amount of carbon dioxide is measured e.g. by infrared

spectrometry, thermal conductivity detection, or other suitable techniques.

The TIC is determined separately from another sub-sample by means of acidification and purging of the

released carbon dioxide. The carbon dioxide shall be measured by one of the techniques mentioned

above.

NOTE Alternatively, for soil, the carbon present as carbonate (TIC) can be determined according to e.g.

ISO 10693 (volumetric method).
4.2 Method B (direct procedure)

In this procedure, the TIC present in the sample are previously removed by treating the sample with

acid. The carbon dioxide released by the following combustion step is measured by one of the

techniques mentioned in 4.1 and indicates the TOC directly.
4.3 Applicability of Methods A or B

Methods A and B have the same applicability for the determination of TOC and/or the determination of

the TIC to TOC ratio. In samples with relatively high TIC contents method B should be applied.

Method B can lead to incorrect results in the following cases:

— the sample contains volatile substances that evaporate during the acidification (e.g. volatile

hydrocarbons from sludge of oil separators);

— side reactions between the sample and the acid take place (e.g. decarboxylation, volatile reaction

products).

NOTE The quality of results of Method B is dependent on experience and practice, especially regarding the

steps before the determination of TOC. Use of automatic dispensing units regarding removal of TIC prior to

determination of TOC can improve the performance of Method B.
5 Interferences

Volatile organic substances can be lost during sample preparation. If necessary, the carbon content

resulting from volatile organic substances shall be determined separately.

Depending on the laboratory experience with samples containing high amounts of TIC, the procedures

can lead to unreliable TOC results if the TIC to TOC ratio is very high (e.g. ≥ 10).

Depending on the detection method used, different interferences can occur, for instance:

— the presence of cyanide can interfere with the coulometric detection of TIC by modifying the pH

value (dissolution of HCN);

— high content of halogenated compounds can lead to an overestimation of TOC when coulometric

detection is used; in some cases the classical silver or copper trap can be insufficient to absorb all

halides.

When present, elemental carbon, carbides, cyanides, cyanates, isocyanates, isothiocyanates and

thiocyanates are determined as organic carbon using the methods described in this document. An

interpretation of the measured value can therefore be problematic in cases where the sample contains

relevant levels of the above-mentioned components. If needed, these components shall be determined

separately by means of a suitable validated method and be recorded in the test report.

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6 Reagents
Use only reagents of recognized analytical grade, unless otherwise specified.
Hygroscopic substances shall be stored in a desiccator.
6.1 Calcium carbonate, CaCO .
6.2 Sodium carbonate, Na CO , anhydrous.
2 3
6.3 Tetrasodium ethylenediamine tetraacetate-tetra-hydrate, Na4-EDTA ∙ 4 H2O
(C H N O Na ∙ 4 H O), heated at 80 °C for 2 h.
10 12 2 8 4 2

Other forms of Na -EDTA hydrates may be used if the water content is exactly known. In these cases,

the composition of the control mixtures shall be recalculated accordingly (see also 6.10 and 6.11).

6.4 Potassium hydrogen phthalate, C H O K.
8 5 4
6.5 Acetanilide, C8H9NO.
6.6 Atropine, C H NO .
17 23 3
6.7 Spectrographic graphite powder, C.
6.8 Sodium salicylate, C7H5O3Na.
6.9 Aluminium oxide, Al2O3, neutral, granular size < 200 µm, annealed at 600 °C.

6.10 Control mixture A, prepared from sodium carbonate (6.2), Na -EDTA ∙ 4 H O (6.3)

4 2
and aluminium oxide (6.9) in a mass ratio of 2,34 : 1,00 : 7,28.

The mixture shall be homogenized. It should contain 25,00 g/kg TIC and 25,00 g/kg TOC (e.g. 22,06 g of

sodium carbonate, 9,41 g Na -EDTA ∙ 4 H O, 68,53 g of aluminium oxide).
4 2

6.11 Control mixture B, prepared from sodium salicylate (6.8), calcium carbonate (6.1), Na4-

EDTA · 4 H2O (6.3) and aluminium oxide (6.9) in a mass ratio of 1,00 : 4,36 : 1,97 : 8,40.

The mixture shall be homogenized. It should contain 33,3 g/kg TIC and 66,6 g/kg TOC (e.g. 6,36 g of

sodium salicylate, 27,78 g of calcium carbonate, 12,50 g of Na -EDTA · 4 H O, 53,36 g of aluminium

4 2
oxide).

6.12 Non-oxidizing mineral acid, used for carbon dioxide expulsion, e.g. phosphoric acid

H PO (w = 85 %).
3 4

NOTE Due to potential corrosion by hydrochloric acid, phosphoric acid is preferred for TIC determination in

Method A (9.1.3). Due to potential formation of P O during combustion, hydrochloric acid is preferred for

4 10
removal of inorganic carbon in Method B (10.1.2).

6.13 Carrier gas, e.g. synthetic air, nitrogen, oxygen or argon, free of carbon dioxide and

organic impurities in accordance with the manufacturer's instructions.
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7 Apparatus
7.1 Precision balance, accurate to at least 0,5 % of test portion weight.
7.2 Equipment for determination of carbon in solids, with relevant accessories.
7.3 Purging unit for TIC determination, for Method A only.
7.4 Vessels, made of e.g. ceramic, silica, quartz, silver or platinum.

NOTE Tin and nickel vessels are not acid-resistant. Tin vessels are suitable only for Method A.

8 Sample pre-treatment

Pre-treat the sample according to EN 16179 or EN 15002, if not otherwise specified.

For solid materials, dried samples shall be used.
NOTE 1 The drying method can affect the result.

Moist or paste-like waste samples may be mixed with aluminium oxide (6.9) until granular material is

obtained and then be comminuted. In this case, the ratio of aluminium oxide to sample shall be

considered in the calculation of TOC (according to 9.4 or 10.4).

If samples contain – depending on the accuracy of the method – negligible amounts of volatile

compounds except water, the samples may be dried.

NOTE 2 For waste samples, the homogeneity is important and often the aluminium oxide step is helpful. More

information is given in Annex B.
9 Procedure – Method A (indirect method)
9.1 Determination
9.1.1 General

The mass of the test portion should be as large as possible and shall be chosen so that the liberated

quantity of carbon dioxide lies within the working range of the equipment/calibration.

9.1.2 Determination of the TC

The sample prepared according to Clause 8 is weighed into a suitable vessel (7.4). To minimize carbon

blank values the vessel may be pre-treated by heating (in a muffle furnace or the TC apparatus itself).

The sample is combusted or decomposed in a flow of carrier gas containing oxygen (6.13).

The combustion temperature should be high enough to convert all carbon completely to carbon dioxide.

NOTE For samples containing carbonates, which are difficult to decompose, e.g. barium carbonate, the

release of the carbon dioxide can be improved by increasing the temperature or by the use of modifiers, e.g. tin,

copper (see B.1)

The temperature range of commercially available instruments is between 900 °C and 1500 °C.

During the combustion of reactive samples, explosion or fuming can be prevented by covering the

sample with inert material e.g. silica sand.

The amount of carbon dioxide released during the combustion is measured e.g. by infrared

spectrometry, thermal conductivity detection, or other suitable techniques, and is expressed as total

carbon (TC).
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9.1.3 Determination of the TIC

The sample prepared according to Clause 8 is weighed into the purging unit (7.3) or in the sample

vessel (7.4).

The system is closed gas-tight and flushed with carrier gas until no more carbon dioxide from ambient

air is present. Then acid (6.12) is added and the carbon dioxide is stripped by purging or stirring and/or

heating. The released carbon dioxide is transferred to the detector by the carrier gas.

The addition of wetting agents, e.g. surfactants, can improve wetting of the surface of the sample.

The addition of anti-foaming agents, e.g. silicone oil, can be helpful in the case of strongly foaming

samples.

The amount of carbon dioxide released during the gas evolution is measured e.g. by infrared

spectrometry, thermal conductivity detection, or other suitable techniques and is expressed as total

inorganic carbon (TIC).
NOTE TIC can alternatively be determined according to e.g. ISO 10693.

Samples containing persistent carbonates (e.g. concrete, cement) require treatment with hot acid for

complete release of carbon dioxide according to manufacturers' instructions.
9.2 Calibration

If a relative method is used for detection, e.g. infrared detection, calibration is necessary.

Calibration is to be performed according to the manufacturer's instruction.

Examples of calibration substances suitable for TC are calcium carbonate (6.1), potassium hydrogen

phthalate (6.4), acetanilide (6.5), atropine (6.6), spectrographic graphite powder (6.7).

The following procedure should be applied for calibration:
— Establish the preliminary working range.

— Measure a minimum of five standard samples. Typically, different sample weights of one calibration

substance are used to cover the calibration range. The absolute amount of carbon of these standard

samples shall be distributed evenly over the working range.

— Carry out a linear regression analysis and test the linearity of the calibration function (see also

ISO 8466-1).

— Use the calibration function for calculating the mean values of the recovery of each standard

sample.

The function shall be linear. Otherwise, the working range shall be restricted to the linear range.

If an absolute method is used for detection, e.g. coulometry, only control measurements according to 9.3

shall be carried out.

This calibration should be carried out for initial validation purposes or after major changes of the

equipment.
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9.3 Control measurements

Control measurements should be carried out using control mixture A (6.10) for the procedures

according to 9.1.2 (TC) and 9.1.3 (TIC). Analysis of one concentration from the middle of the respective

working range, possibly repeated two or three times, is sufficient. For the TC and TIC the mean recovery

shall be between 80 % and 120 % with a coefficient of variation ≤ 5 %.
Blank values shall be taken into account, if necessary.

If the required recoveries are not achieved, the following measures can be helpful.

For TC analysis:
— checking the homogeneity of the control mixture;
— checking the calibration;
— increasing the temperature during release of carbon dioxide;
— reducing the flow of the carrier gas;
— encouraging a turbulent flow in the combustion tube;
— use of modifiers;
— use of catalysts for post-oxidation of combustion gases.
For TIC analysis:
— optimizing the stirring speed and/or the gas flow in the purging vessel;
— improving the gas exchange in the purging vessel;
— avoiding condensation in the system.
9.4 Calculation and expression of results
The TC and TIC mass contents are calculated from
— calibration function and sample mass if relative detection methods are used,
— specific constants and sample mass if absolute detection methods are used.

The calculation of TOC is achieved from the difference of the mean values of TC and TIC according to

Formula (1):
m Fm− m (1)
( )
TOC TC TIC
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In case of mixing the sample with aluminium oxide (see Clause 8) a dilution factor following

Formula (2) shall be used:
m + m
F= (2)
where

is the TOC content as carbon in the sample expressed in grams per kilogram (g/kg);

TOC

is the mean value of the TC content as carbon in the sample, prepared according to Clause 8

expressed in grams per kilogram (g/kg);

is the mean value of the TIC content as carbon in the sample prepared according to Clause 8

TIC
expressed in grams per kilogram (g/kg);

is the dilution factor resulting from the sample preparation of the sample according to

Clause 8;
is the mass of the sample expressed in grams (g);
is the mass of aluminium oxide expressed in grams (g).
The TOC value resulting from Formula (1) is calculate
...

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