🌿 Determination of total organic carbon (TOC) in waste, sludges and sediments — Method A (indirect): TOC as the difference between total carbon (TC, combustion in oxygen) and total inorganic carbon (TIC, release of CO2 by acid), Method B (direct): combustion of the sample after removal of carbonates with acid; undried samples, content above 1 g carbon per kg dry matter, PN-EN 13137 (withdrawn)

Environment PN-EN 13137

Overview

WHAT THE STANDARD COVERS. Scope from the PKN catalogue card of PN-EN 13137:2004 (Polish version), in full (our translation): “Two methods (direct and indirect) are specified for the determination of total organic carbon in wet waste samples containing more than 1 g carbon per 1 kg dry matter, which can also be applied to sludges, other sediments and comparable materials”. We read the text of the standard in the sample of SIST EN 13137:2002 (the text of EN 13137:2001 without changes) from the title page through the contents, foreword, introduction and Clauses 1–9 up to and including 10.5 of Clause 10 (Method A); where the text output loses the inequality signs, we read the page images. Outside the sample remain: 10.6 (evaluation of Method A), the whole of Clause 11 (Method B — procedure), Clause 12 (performance characteristics), 13 (test report) and Annex A (additional results of inter-laboratory tests).

ACCORDING TO THE TEXT OF EN 13137:2001 (Clauses 1–9, 10.1–10.5). The standard was prepared by CEN/TC 292 “Characterization of waste” (secretariat NEN). Introduction: organic carbon in waste, sludges and sediments occurs in many forms and not all components can be determined individually, so a sum parameter is measured — TOC; the parameter may be used for assessing the suitability of waste for landfilling. Scope (1): two methods for TOC in undried waste samples containing more than 1 g carbon per kg dry matter (0.1 %); also sludges, sediments and comparable materials. Elemental carbon, carbides, cyanides, cyanates, isocyanates, isothiocyanates and thiocyanates are determined by these methods as organic carbon — where the waste contains relevant levels of them, interpretation of the result may be problematical, and these components shall, if needed, be determined separately and reported (at the time of publication no standardized procedure for elemental carbon in waste existed). Definitions (3): total carbon (TC) — quantity of carbon present in organic, inorganic and elemental form; total inorganic carbon (TIC) — quantity of carbon liberated as CO2 by acid treatment; total organic carbon (TOC) — quantity of carbon converted into CO2 by combustion and not liberated as CO2 by acid treatment; the definitions apply only in this standard and do not fully comply with scientific ones. Principle (4): Method A (indirect) — TOC as the difference between TC and TIC; TC of the undried sample is burned in an oxygen-containing gas flow free of CO2 (catalysts and modifiers may be used for complete combustion), and CO2 is measured by infrared spectrometry, gravimetry, coulometry, conductometry, thermal conductivity detection, flame ionization detection after reduction to methane or another suitable technique; TIC is determined separately, from another sub-sample, by acidification and purging of CO2. Method B (direct) — carbonates are removed with acid before combustion, and the CO2 from combustion gives TOC directly. Applicability (4.3): both methods have the same applicability as regards TOC content and the TIC to TOC ratio; Method B may give incorrect results when the sample contains volatile substances that evaporate during acidification (e.g. volatile hydrocarbons from sludge of oil separators) or when side reactions with the acid take place (e.g. decarboxylation, volatile reaction products); if these can be excluded, both methods give comparable results, and in case of doubt Method A should be preferred; the quality of Method B results depends more on experience, especially in the steps before combustion. Interferences (5): volatile organic substances may be lost during preparation — if necessary they are determined separately; at a very high TIC to TOC ratio (e.g. ≥ 10) the TOC result may be unreliable; cyanide can interfere with coulometric TIC detection by changing the pH (dissolution of HCN), and a high content of halogenated compounds can overestimate TOC with coulometric detection, because a silver or copper trap may not absorb all halides. Hazards (6): samples may ferment and be infectious, gases from microbial activity may be flammable, and pressure build-up may burst the container; harmful compounds arise during combustion and acid treatment (precautions, e.g. activated carbon filters); samples with high organic content may explode on introduction into the furnace — a smaller portion or covering with inert material helps. Reagents (7): calcium carbonate, anhydrous sodium carbonate, tetrasodium EDTA tetrahydrate (heated 2 h at 80 °C), potassium hydrogen phthalate, sodium salicylate, neutral aluminium oxide < 200 µm annealed at 600 °C; control mixture A — sodium carbonate, Na4-EDTA·4H2O and aluminium oxide in the mass ratio 2.34 : 1.00 : 1.97, containing 50.00 g/kg each of TIC and TOC (e.g. 44.13 g + 18.83 g + 37.04 g); control mixture B — sodium salicylate, calcium carbonate, Na4-EDTA·4H2O and aluminium oxide in the ratio 1.00 : 4.36 : 1.97 : 8.40, containing 33.3 g/kg TIC and 66.6 g/kg TOC; a non-oxidizing mineral acid for expelling CO2, e.g. phosphoric acid (w = 85 %); synthetic air, nitrogen, oxygen, argon free of CO2 and organic impurities. Equipment (8): homogenization devices, analytical balance accurate to at least 0.5 % of the test portion mass, apparatus for the determination of carbon in solids, purging unit for TIC (Method A only). Storage (9): glass or other suitable containers; biologically active samples are analysed immediately or stored at −18 °C at most. Preparation (10.1): samples as homogeneous as possible and undried; solids are comminuted without heating, preferably below 200 µm; moist or paste-like samples are mixed with aluminium oxide until granular and comminuted, and the ratio of aluminium oxide to sample is considered in the calculation; if the sample contains, apart from water, negligible amounts of volatile compounds, it may be dried at 105 °C, and liquid sludges (especially sewage sludge) — freeze-dried; then the test report shall state “sample dried at 105 °C” or “sample dried by freeze drying”. Water content (10.2) is determined on a separate sub-sample: without volatile compounds — from dry matter according to ISO 11465 or EN 12880, with volatile compounds otherwise, e.g. by distillation according to ISO 3733 or by Karl Fischer according to ISO 6296. Determination (10.3): the standard gives no recommendation on apparatus design; the test portion as large as possible so that the CO2 lies within the working range; TC and TIC at least twice — the difference of two results should be ≤ 10 % of the mean, otherwise at least one further determination and the coefficient of variation should be ≤ 10 %, and if it is greater, it is reported with the result. TC (10.3.2): boat or crucible (e.g. ceramics, silica glass, platinum, tin), which may be pre-heated for a low blank; combustion in an oxygen-containing carrier gas at a temperature high enough for complete conversion to CO2; for carbonates difficult to decompose (e.g. barium) — higher temperature or modifiers (e.g. tin, copper); commercial instruments work at 900–1500 °C; reactive samples covered with inert material, e.g. silica sand. TIC (10.3.3): portion in the purging vessel, flushing with carrier gas to remove CO2 from air, addition of acid and stripping of CO2 by gas flow, stirring or heating; antifoam (e.g. silicone oil) for foaming samples, wetting agent for poor wetting. Calibration (10.4): with relative detection (e.g. infrared) — for TC e.g. calcium carbonate or potassium hydrogen phthalate, for TIC sodium or calcium carbonate; sodium carbonate, Na4-EDTA and compounds with EDTA structure shall not be used for calibration, as they serve for control; at least five (recommended ten) standards evenly over the range, each at least in triplicate, linear regression and linearity test according to ISO 8466-1 — if not linear, the range is restricted to the linear part; with absolute detection (e.g. coulometry) control measurements suffice; calibration at initial validation or after major changes of the equipment. Control (10.5): each working day with control mixture A for TC and TIC — one concentration from the middle of the range three times; the mean recovery shall be between 90 % and 110 % with a coefficient of variation not greater than 5 %; with control charts one measurement per batch suffices; a blank is determined for all equipment and reagents. If recoveries are not achieved, for TC e.g. a higher combustion temperature, lower carrier gas flow, turbulence in the tube, modifiers and post-oxidation on catalysts help; for TIC — a higher temperature during CO2 release, better stirring or flow, better gas exchange and avoiding condensation.

STATUS (catalogue cards as of 03.10.2026). The card of PN-EN 13137:2004 (Polish version, published 08-07-2004, 20 pages, price group K) has the header “Withdrawn”: withdrawal date 22-01-2018; Health, Environment and Medicine Sector, KT 216 Waste, ICS 13.030.01, “Introduces: EN 13137:2001 [IDT]”, “Supersedes: PN-EN 13137:2002 — English version”. The card has no “Replaced by” field. The card of PN-EN 13137:2002 (English version) — “Withdrawn” 08-07-2004, “Replaced by: PN-EN 13137:2004 — Polish version”. In the iTeh catalogue (read 03.10.2026) the Slovenian adoption SIST EN 13137:2002 has the entry “Replaced By: SIST EN 15936:2012” dated 01.05.2019 — in Slovenia the successor is the adoption of EN 15936 (total organic carbon in sludge, treated biowaste, soil and waste by dry combustion). At PKN there is no such link: the cards of PN-EN 15936:2013-02 (withdrawn 20-07-2022) and PN-EN 15936:2022-07 (current, KT 191 Soil Chemistry) do not list PN-EN 13137 in the “Supersedes” field, and the card of PN-EN 13137:2004 has no “Replaced by” field (on PN-EN 15936 — a separate entry). Note: PN-EN ISO 13137 is a different standard — according to the PKN search (03.10.2026) the 2023-04 edition is titled “Workplace atmospheres — Pumps for personal sampling of chemical and biological agents — Requirements and test methods”; the number alone without “ISO” does not denote it.

HOW MANY LABORATORIES AND IN WHAT FORM (copy of the accreditation scope database, load up to 17.09.2026, read 03.10.2026). The number 13137 (without “ISO”) appears in 15 records at 6 laboratories: AB 054, AB 300, AB 418, AB 550, AB 646, AB 769. In the current scopes on the PCA website (read 03.10.2026, issues from 26.01.2026 to 22.09.2026) all give “PN-EN 13137:2004”, and AB 550 in two of three items the designation alone without year. The “Laboratories” tab (“PN-EN 13137”) shows the same 6 laboratories; checked with the tab query on the production server labcoda.pl on 03.10.2026.

WHAT THE LABORATORIES TEST (PCA items). Waste (including with codes according to the waste catalogue), sludges and sewage sludge, bottom sediments, coal shales and mudstones (AB 054), aggregates and construction materials (sand, aggregate, slag — AB 418), solid fuels and solid recovered fuels (AB 300, AB 550). Technique: high-temperature combustion with infrared detection. The scopes show which method the laboratory uses: AB 300 measures TC (5–950) g/kg and TIC (5–250) g/kg and gives TOC “by calculation” — this is Method A; AB 550 for recovered fuels measures inorganic carbon and gives TOC “by calculation”; AB 054 for industrial waste measures TC and TOC (0.01–95.0) % and gives TIC “by calculation”, i.e. determines TOC directly (Method B), while for shales and mudstones it measures all three (TIC 0.01–35.0 %); AB 646 gives TOC and TC (1.0–400) g/kg and inorganic carbon (1.0–120) g/kg and cites jointly PN-ISO 10694:2002 (entry on PN-ISO 10694); AB 418 — only TOC (5000–800 000) mg/kg, AB 769 — only TOC (7–500) g/kg. The lower limit of AB 054 — 0.01 % — is ten times lower than the applicability threshold of Clause 1 (above 1 g/kg dry matter, i.e. 0.1 %); the lower limit of AB 646 — 1.0 g/kg — lies exactly at this threshold. The scope does not state whether the percentages and g/kg refer to dry matter.

WHERE A SEEMINGLY CORRECT RESULT IS EASY. At storage and preparation: a biologically active sample, neither analysed immediately nor frozen to −18 °C, does not meet the condition of Clause 9; drying at 105 °C or freeze-drying removes volatile organic compounds that belong to TOC — therefore only samples without relevant amounts of volatile compounds may be dried, and this must be stated in the report (10.1, 5); aluminium oxide added to a paste-like sample dilutes it, and without considering the mass ratio the result will be too low (10.1). At measurement: in Method B the acid expels volatile hydrocarbons together with CO2 from carbonates — TOC is too low, and the laboratory does not see it because it does not measure TIC (4.3); at a very high TIC to TOC ratio (e.g. ≥ 10) in Method A, TOC is a small difference of two large numbers and any error of TC or TIC passes into the result (5); for carbonates difficult to decompose, too low a combustion temperature lowers TC (10.3.2); halogenated compounds with coulometric detection overestimate TOC (5). At calculation: in Method A TOC is not a measurement but the difference of two measurements of the same method on two portions — TC from combustion (10.3.2) and TIC from acidification (10.3.3); in Method B the measurement is TOC, and TIC — if the laboratory reports it — is the difference of TC and TOC. At the result: elemental carbon, carbides, cyanides, cyanates, isocyanates, isothiocyanates and thiocyanates count here as organic carbon (1) — at relevant contents the result must be interpreted with care and these components determined separately if needed; the result refers to dry matter, so the water content from a separate portion (10.2) is part of the calculation.

WHAT WE DO NOT GIVE. We did not read 10.6 and Clauses 11–13, so we do not give the calculation formulas, the procedure of Method B, the performance characteristics or report requirements beyond the statement on drying of 10.1. We do not compare this standard with PN-EN 15936 — we did not read the text of EN 15936 for this entry. Nor do we give TOC criteria for the acceptance of waste at landfills, because we did not read the text of the regulation.

Method principle

Organic carbon in an undried sample is determined by conversion into carbon dioxide and its measurement (e.g. by infrared). In Method A a portion is burned in oxygen (total carbon, TC), and from a second portion CO2 is released from carbonates by acid (total inorganic carbon, TIC); TOC = TC − TIC. In Method B carbonates are removed with acid before combustion, and the measured CO2 gives TOC directly.

Applications

• Waste, sludges, sewage and bottom sediments and similar materials with carbon content above 1 g/kg dry matter (Clause 1)
• Assessment of the suitability of waste for landfilling — TOC as a sum parameter (introduction)
• Aggregates, construction materials, coal shales and mudstones, recovered fuels — in the accreditation scopes of 6 laboratories at PCA

Key parameters

Standard

Standard number

PN-EN 13137:2004

Title (PL)

Charakteryzowanie odpadów — Oznaczanie ogólnego węgla organicznego (OWO) w odpadach, szlamach i osadach

Title (EN)

Characterization of waste — Determination of total organic carbon (TOC) in waste, sludges and sediments

Step-by-step procedure

1. Storage and preparation

   Biologically active samples analysed immediately or stored at ≤ −18 °C; comminute without heating (< 200 µm), granulate paste-like samples with aluminium oxide; dry only samples without volatile organic compounds. PN-EN 13137:2004 withdrawn 22-01-2018 (PKN catalogue card as of 03.10.2026).

2. Water content

   On a separate portion: from dry matter (ISO 11465, EN 12880) or with volatile compounds by distillation (ISO 3733) or Karl Fischer (ISO 6296).

3. Measurement of TC (Method A) or TOC (Method B)

   Combustion of the portion in oxygen-containing gas and measurement of CO2; in Method B carbonates are removed with acid before combustion; at least two determinations, difference ≤ 10 % of the mean.

4. Measurement of TIC (Method A)

   Portion in the purging vessel, flushing with gas, acid, purging and measurement of CO2; at least two determinations.

5. Calibration and control

   Standards: calcium carbonate or potassium hydrogen phthalate (TC), sodium or calcium carbonate (TIC); daily control mixture A — recovery 90–110 %, coefficient of variation ≤ 5 %. Evaluation (10.6) outside the sample read.

Required equipment and apparatus

Reagents, media and consumables

Health and safety (OHS)

• Samples may ferment and be infectious; gases from microbial activity may be flammable, and pressure build-up may burst the container and scatter contaminated fragments (Clause 6)
• Harmful compounds arise during combustion and acidification — precautions, e.g. activated carbon filters (Clause 6)
• Samples with high organic content may explode on introduction into the furnace — smaller portion or covering with inert material (Clause 6)

Frequently asked questions