ISO 17505:2025

Soil and waste characterization - Temperature dependent differentiation of total carbon (TOC400, ROC, TIC900)

This document specifies a method for the differentiated determination of the organic carbon content (TOC400) which is released at temperatures up to 400 °C, the residual oxidizable carbon (ROC) (including e.g. lignite (brown coal), hard coal, charcoal, black carbon, soot) and the inorganic carbon (TIC900) which is released at temperatures up to 900 °C. The basis of this method is the dry combustion or decomposition of carbon to CO2 in the presence of oxygen or non-oxygen conditions using temperatures ranging from 150 °C to 900 °C in dry solid samples of sediment, soil, soil with anthropogenic admixtures and solid waste (see Table 1) with carbon contents of more than 1 g per kg (0,1 % C) (per carbon type in the test portion). NOTE TIC900’ includes the TIC measured after acid addition e.g. by ISO 10694 or EN 15936. TOC400 is a fraction of TOC measured according to e.g. ISO 10694 or EN 15936.

Caractérisation des sols et des déchets — Différenciation en fonction de la température du carbone total (COT400, COR, CIT900)

General Information

• Status: Published
• Publication Date: 03-Jun-2025
• ICS: 13.080.10 - Chemical characteristics of soils
• Technical Committee: ISO/TC 190/SC 3 - Chemical and physical characterization
• Drafting Committee: ISO/TC 190/SC 3 - Chemical and physical characterization
• Current Stage: 6060 - International Standard published
• Start Date: 04-Jun-2025
• Due Date: 07-May-2025
• Completion Date: 04-Jun-2025

Overview

ISO 17505:2025 - Soil and waste characterization: Temperature dependent differentiation of total carbon (TOC400, ROC, TIC900) specifies a thermal-gradient method to differentiate carbon fractions in dry solid samples (sediment, soils, urban soils, tailings, wastes such as incineration ash, foundry sand and construction waste). The method is based on dry combustion/decomposition to CO2 across a programmed temperature range (approximately 150 °C to 900 °C) to quantify:

• TOC400 - organic carbon released up to 400 °C
• ROC - residual oxidizable carbon (e.g., lignite, hard coal, charcoal, black carbon/soot), measured according to temperature plateaus (600 °C or 900 °C depending on method)
• TIC900 - inorganic carbon released up to 900 °C (including TIC after acid stripping)

The standard applies to samples containing more than 1 g/kg (0.1 % C) per carbon type in the test portion and supports CO2 detection by infrared or other CO2-sensitive sensors.

Key Topics and Requirements

• Principle: Temperature-gradient thermal oxidation/decomposition with switching between oxidizing and non-oxidizing carrier gases for selective carbon release.
• Two procedural variants:
  • Method A: oxidative measurement sequence (TOC400 → ROC600 → TIC900A)
  • Method B: mixed oxidative/non-oxidative sequence (used for ROC900 and TIC900B distinctions)
• Temperature control: defined plateaus (±20 °C) and minimum holding times for peak integration.
• Interferences addressed: carbides, sulfur and nitrogen compounds, carbonates (which can decompose across ranges), catalytic substances, premature releases/deflagrations, and peak-baseline issues.
• Quality elements: sample pretreatment, calibration, system control standards, reagents, apparatus specifications, measurement, evaluation, expression of results and reporting. Annex A covers performance characteristics; Annex B covers cooling procedures for method B.

Practical Applications and Who Uses It

ISO 17505:2025 is used for environmental assessment and materials characterization where a differentiated understanding of carbon forms is needed:

• Environmental and commercial analytical laboratories conducting soil and waste carbon analysis
• Landfill operators and waste managers assessing disposal/recycling suitability and hazard potential
• Soil scientists and remediation consultants evaluating carbon stability and pyrogenic (black) carbon content
• Regulatory agencies and consultants performing compliance testing or interpreting TOC/TIC-based criteria

Differentiating TOC400, ROC and TIC900 helps distinguish labile organic carbon from persistent pyrogenic carbon and inorganic carbon-useful for risk assessment, carbon accounting and management decisions.

Related Standards

• ISO 10694 / EN 15936 - Methods for TOC/TIC by acid stripping (TIC after acid addition referenced)
• EN 16179, EN 15002, ISO 11464 - Sample pretreatment and preparation standards referenced in ISO 17505:2025

Keywords: ISO 17505:2025, TOC400, ROC, TIC900, soil and waste characterization, temperature dependent differentiation, thermal oxidation, CO2 detection, carbon fractions, environmental laboratory.

Standards Content (Sample)

International
Standard
ISO 17505
First edition
Soil and waste characterization —
2025-06
Temperature dependent
differentiation of total carbon
(TOC , ROC, TIC )
400 900
Caractérisation des sols et des déchets — Différenciation en
fonction de la température du carbone total (COT , COR, CIT )
400 900
Reference number
© ISO 2025
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or ISO’s member body in the country of the requester.
ISO copyright office
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Published in Switzerland
ii
Contents Page
Foreword .iv
Introduction .v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Principle . 2
5 Interferences . 3
5.1 Interference due to carbides .3
5.2 Interference due to sulfur and nitrogen compounds .3
5.3 Interference due to carbonates .3
5.4 Peak not reaching the baseline .5
5.5 Difficulties in separating ROC peak and TIC peak .6
600 900A
5.6 Interferences due to premature releases and deflagrations .7
5.7 Interferences due to catalytic active substances in samples .7
6 Reagents . 7
6.1 General .7
6.2 Standards for system control .8
7 Apparatus . 8
8 Procedure . 9
8.1 General .9
8.2 Sample preparation and processing .9
8.3 Calibration .9
8.4 Measurement (oxidative method A) .9
8.5 Measurement (mixed oxidative/non-oxidative method B) .10
9 Evaluation .11
9.1 General .11
9.2 Control measurements . 13
10 Expression of results .13
11 Test report .13
Annex A (informative) Performance characteristics . 14
Annex B (informative) Cooling procedure for method B .21
Bibliography .22

iii
Foreword
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The procedures used to develop this document and those intended for its further maintenance are described
in the ISO/IEC Directives, Part 1. In particular, the different approval criteria needed for the different types
of ISO documents should be noted. This document was drafted in accordance with the editorial rules of the
ISO/IEC Directives, Part 2 (see www.iso.org/directives).
ISO draws attention to the possibility that the implementation of this document may involve the use of (a)
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This document was prepared by the European Committee for Standardization (CEN) (as EN 17505:2023)
and was adopted, without modifications other than those given below, by Technical Committee ISO/TC 190,
Soil quality, Subcommittee SC 3, Chemical and physical characterization under the fast-track procedure.
— EN ISO 10693 references have been changed to ISO 10693;
— EN 15936 has been added to the Bibliography;
— cross references in 6.2 have been corrected.
Any feedback or questions on this document should be directed to the user’s national standards body. A
complete listing of these bodies can be found at www.iso.org/members.html.

iv
Introduction
Carbon occurs in soils and materials similar to soil in a variety of compounds and forms. When determining
carbon in soils or soil-like materials, an overall determination of the different mass fractions is most
feasible. The summarized declaration of carbon is yet done by differentiating organic and inorganic carbon
(EN 15936, ISO 10694). In the proportion classified as “organic carbon”, a fraction of very stable highly
aromatic and highly condensed carbon compounds can be present, sometimes in significant mass fractions.
Since this black (pyrogenic) carbon is only very slowly decomposed and released, its environmental
relevance has to be differently evaluated than the proportions of organic carbon which are faster chemical-
biologically decomposed. The environmental relevance is estimated if e.g. the suitability of soils and soil-
like materials for disposal in landfill is assessed. For a differentiated assessment, a separate declaration
of the different mass fractions of organic, black (pyrogenic) and inorganic carbon is necessary. Using the
specified temperature-gradient method and utilizing the combustion characteristic(s), the carbon fractions
established according to this standard in soil and soil-like materials can be differentiated.
In respect of the hazard potential, the content of solely organically bonded carbon in solids determined with
the described method can be important for disposal and/or recycling.
The method has been validated with the materials listed in Table 1, see also Annex A.
Table 1 — Materials used for validation
Material type Materials used for validation
soils from natural material mineral soils
soil with anthropogenic admixtures (urban soils)
tailing material (tailings) tailing material from coal mining
sediment sediment
waste waste incineration ash
foundry sand
construction waste
v
International Standard ISO 17505:2025(en)
Soil and waste characterization — Temperature dependent
differentiation of total carbon (TOC , ROC, TIC )
400 900
1 Scope
This document specifies a method for the differentiated determination of the organic carbon content
(TOC ) which is released at temperatures up to 400 °C, the residual oxidizable carbon (ROC) (including
e.g. lignite (brown coal), hard coal, charcoal, black carbon, soot) and the inorganic carbon (TIC ) which is
released at temperatures up to 900 °C.
The basis of this method is the dry combustion or decomposition of carbon to CO in the presence of oxygen
or non-oxygen conditions using temperatures ranging from 150 °C to 900 °C in dry solid samples of sediment,
soil, soil with anthropogenic admixtures and solid waste (see Table 1) with carbon contents of more than 1 g
per kg (0,1 % C) (per carbon type in the test portion).
NOTE TIC includes the TIC measured after acid addition e.g. by ISO 10694 or EN 15936. TOC is a fraction of
900’ 400
TOC measured according to e.g. ISO 10694 or EN 15936.
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 16179, Sludge, treated biowaste and soil — Guidance for sample pretreatment
EN 15002, Characterization of waste — Preparation of test portions from the laboratory sample
ISO 11464, Soil quality — Pretreatment of samples for physico-chemical analysis
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
ISO and IEC maintain terminology databases for use in standardization at the following addresses:
— ISO Online browsing platform: available at https:// www .iso .org/ obp
— IEC Electropedia: available at https:// www .electropedia .org/
3.1
total organic carbon which is released up to 400 °C
TOC
quantity of carbon which is determined in the range between 150 °C − (400 ± 20) °C to the 1st signal minimum
after the minimum holding time at (400 ± 20) °C, in the case of dry combustion in the presence of oxygen
Note 1 to entry: TOC is a fraction of TOC measured e.g. by ISO 10694 or EN 15936.
3.2
residual oxidizable carbon measured at 600 °C
ROC
quantity of carbon which is determined between the signal minima at (400 ± 20) °C and at (600 ± 20) °C
after the minimum holding time at (600 ± 20) °C, in the case of dry combustion in the presence of oxygen
following method A (procedure see 8.4)
Note 1 to entry: ROC may differ from ROC for some materials.
600 900
3.3
residual oxidizable carbon measured at 900 °C
ROC
quantity of carbon which is determined during dry combustion in the presence of oxygen after the completed
carbon release for the TOC and TIC measurement at (900 ± 20) °C to the first signal minimum after
400 900B
the minimum holding time at (900 ± 20) °C following method B (procedure see 8.5)
Note 1 to entry: ROC may differ from ROC for some materials.
900 600
3.4
total inorganic carbon which is released up to 900 °C in the presence of oxygen
TIC
900A
quantity of carbon which is determined between the signal minima at (600 ± 20) °C and at (900 ± 20) °C
after the minimum holding time at (900 ± 20) °C, in the case of dry combustion in the presence of oxygen
following method A (procedure see 8.4)
Note 1 to entry: TIC may differ from TIC for some materials.
900A 900B
3.5
total inorganic carbon which is released up to 900 °C during non-oxidizing conditions
TIC
900B
quantity of carbon which is determined during non-oxidizing conditions between the signal minima at
(400 ± 20) °C and at (900 ± 20) °C after expiry of the minimum holding time at (900 ± 20) °C before the
ROC measurement following method B (procedure see 8.5)
900B
Note 1 to entry: TIC may differ from TIC for some materials.
900B 900A
3.6
total carbon
TC
quantity of carbon present in the sample representing the sum of organic (TOC ), inorganic (TIC or
400 900A
TIC ) and residual oxidizable carbon (ROC or ROC )
900B 600 900
4 Principle
The determination of organic carbon (TOC ), residual oxidizable carbon (ROC or ROC ) and inorganic
400 600 900
carbon (TIC or TIC ) in solids is affected by thermal oxidation or decomposition of the different
900A 900B
fractions of carbon at different temperatures to CO , if necessary, supported by changing between oxidizing
and non-oxidizing carrier gases.
The application of the gradient method with a suitable temperature program allows the determination of
organic carbon (TOC ), residual oxidizable carbon (ROC) and inorganic carbon (TIC ) and the calculation
400 900
of total carbon (TC) by summing up these contents.
The final analysis of CO can be performed with different methods, e.g. by means of infrared detection or
CO sensitive sensors.
5 Interferences
5.1 Interference due to carbides
Several carbides can interfere with this method.
5.2 Interference due to sulfur and nitrogen compounds
Depending on the measuring technique used, high contents of sulfur or nitrogen compounds can result
in overestimations or underestimations. This can be controlled by means of selected standard samples
(e.g. potassium sulfate, potassium nitrate). Furthermore, the information provided by the equipment
manufacturer shall be considered.
5.3 Interference due to carbonates
The thermal stability of carbonates exhibits a great bandwidth (for examples see Figures 1, 2 and 3).
Therefore, carbonates can be detected in both the TOC peak range and the ROC range. In the presence
400 600
of certain carbonates or carbonate mixtures which decompose at low temperature ranges, the identification
of the TIC peak is sometimes difficult or impossible. Alternatively, the impact of carbonates on the
900A
TOC analysis can be determined by stripping with acid (e.g. ISO 10693 or EN 15936).
Key
X time
Y1 signal intensities
Y2 temperature in °C
Figure 1 — Example diagram FeCO
Key
X time
Y1 signal intensities
Y2 temperature in °C
Figure 2 — Example diagram MnCO ·fH O
3 2
Key
X time
Y1 signal intensities
Y2 temperature in °C
Figure 3 — Example diagram PbCO
5.4 Peak not reaching the baseline
For some materials, the temperature plateau according to the temperature ramp does not last long enough
and the peak does not reach the baseline (see Figure 4). A prolongation of the plateau at the temperature
level can lead to a significantly better return of the signal to the baseline (see Figure 5).
NOTE A homogeneous distribution of the sample in the combustion vessel optimizes the reaction with oxygen.
Key
X time in s
Y1 signal intensities
Y2 temperature in °C
Figure 4 — Example diagram for cases where peaks do not reach the baseline

Key
X time in s
Y1 signal intensities
Y2 temperature in °C
Figure 5 — Example diagram for the prolongation of the temperature plateau so peaks can reach
the baseline
5.5 Difficulties in separating ROC peak and TIC peak
600 900A
If the temperature ramp does not allow the separation (resolution) of the ROC peak from the TIC peak
600 900A
(see Figure 6), the influence of carbonates on the ROC analysis or of ROC on the TIC measurement
600 600 900A
can be determined by stripping with acid (e.g. ISO 10693, EN 15936). Alternatively, the method specified in
8.5 can be used. The method has to be documented with the measuring result.
In the case of deviating determination of TIC by means of acid, the information provided by the
900A
equipment manufacturer should be consulted.

Key
X time
Y1 signal intensities
Y2 temperature in °C
Figure 6 — Difficulties in separating ROC and TIC peaks
600 900A
5.6 Interferences due to premature releases and deflagrations
During the combustion of reactive samples, deflagration or carbon black (soot) formation can occur, and
it is also known that the remaining carbon can undergo premature ignition resulting in superposition
(overlapping) and misidentification. This can be prevented by covering the sample with a layer of inert
material, e.g. quartz sand.
5.7 Interferences due to catalytic active substances in samples
In waste samples from high temperature treatment (e.g. with catalytic active metal contents) the detection
method can lead to overestimated TOC values.
6 Reagents
6.1 General
All reagents used shall be at least of analytical grade and shall be suitable for their specific purposes.
6.1.1 Oxygen, O , purity φ > 99,7 % or synthetic air, purity φ > 99,7 %.
6.1.2 Inert gas, e.g. nitrogen, N , (only for the alternative procedure specified in 8.5).
6.1.3 Calcium carbonate, CaCO .
6.1.4 Activated carbon.
NOTE Activated carbon does not contain 100 % elemental carbon.
6.1.5 Microcrystalline cellulose.

6.1.6 Aluminium oxide, Al O .
2 3
6.1.7 Graphite.
NOTE Graphite does not contain 100 % elemental carbon.
6.2 Standards for system control
For a control standard for method A (8.4) containing 2 % TOC 2 % ROC and 2 % TIC , carefully
400 600 900A
homogenize appropriate amounts of microcrystalline cellulose (6.1.5), CaCO (6.1.3), activated carbon (6.1.4)
and Al O (6.1.6). First comminute the activated carbon (6.1.4) and Al O (6.1.6) in a suitable device.
2 3 2 3
Then add the microcrystalline cellulose (6.1.5) and CaCO (6.1.3) and mix it. In preparing this standard,
appropriate homogenization equipment (7.1) should be used. The standard should be stored in a glass vessel
at a dry place. The stability of the standard should be checked in regular intervals by means of a TC analysis.
EXAMPLE 1 For 10 g of the control standard, carefully homogenize 0,45 g microcrystalline cellulose (6.1.6), 1,67 g
CaCO3 (6.1.4), 0,22 g activated carbon (6.1.5; carbon content 90 % C) and 7,66 g Al2O3 (6.1.7). First comminute the
activated carbon (6.1.5) and Al2O3 (6.1.7) in a suitable device. Then add the microcrystalline cellulose (6.1.6) and
CaCO3 (6.1.4) and mix it. The activated carbon does not contain 100 % elemental carbon. The standard prepared as
above contains 2 % TOC , 2 % ROC and 2 % TIC .
400 600 900A
Depending on matrices of the measured samples in the lab or guidance of the manufacturer of the analyser
other certified system control standards also with different carbon contents can be used. For system check
every carbon fraction (TOC , ROC , TIC ) shall be part of this mixture. These mixtures shall fulfil the
400 600 900A
quality requirements in subclause 9.2.
For a control standard for method B (8.5) containing 2 % TOC , 2 % ROC and 2 % TIC , carefully
400 900 900B
homogenize appropriate amounts of microcrystalline cellulose (6.1.5), CaCO (6.1.3), graphite (6.1.7) and
Al O (6.1.6). First comminute the graphite (6.1.8) and Al O (6.1.6) in a suitable device. Then add the
2 3 2 3
microcrystalline cellulose (6.1.5) and CaCO (6.1.4) and mix it. In preparing this standard, appropriate
homogenization equipment (7.1) should be used. The standard should be stored in a glass vessel at a dry
place. The stability of the standard should be checked in regular intervals by means of a TC analysis.
EXAMPLE 2 For 10 g of the control standard, carefully homogenize 0,45 g microcrystalline cellulose (6.1.5), 1,67 g
CaCO (6.1.3), 0,206 g graphite (6.1.7; carbon content 97 % C) and 7,674 g Al O (6.1.6). First comminute the graphite
3 2 3
(6.1.8) and Al O (6.1.6) in a suitable device. Then add the microcrystalline cellulose (6.1.5) and CaCO (6.1.3) and mix
2 3 3
it. The graphite does not contain 100 % elemental carbon. The standard prepared as above contains 2 % TOC , 2 %
ROC and 2 % TIC .
900 900B
Depending on matrices of the measured samples in the lab or guidance of the manufacturer of the analyser,
other certified system control standards also with different carbon contents can be used. For system check
every carbon fraction (TOC , ROC , TIC ) shall be
...