🧪 TOC—Total Organic Carbon
In short
Guidelines for the determination of total (TOC) and dissolved (DOC) organic carbon in drinking water, ground water, surface water, sea water and waste water: oxidation of organic carbon to carbon dioxide and determination of the CO₂ formed. The test is performed according to PN-EN 1484:1999; Range: 0.3–1000 mg/l of organic carbon; the lower value only with instruments of adequate sensitivity; higher concentrations after dilution. The procedure comprises 6 steps; it is used for: Water intended for human consumption — TOC without abnormal change; not mandatory for supplies below 10 000 m³ per day (Journal of Laws 2026, item 748), Waste water — reference method for TOC (Journal of Laws 2019, item 1311, Annex 12), Monitoring of surface and ground waters (Journal of Laws 2021, item 1576).
At a glance
- Standard: PN-EN 1484:1999
- Category: Physicochemistry
- Procedure steps: 6
- Range: 0.3–1000 mg/l of organic carbon; the lower value only with instruments of adequate sensitivity; higher concentrations after dilution
- Removal of inorganic carbon: acidification to pH below 2 and purging with a gas free from CO₂ and organic compounds (about 5 min) or the differential method TC − TIC
- DOC: 0.45 µm membrane filter, previously washed with hot water
Overview
STATUS (as of 29.10.2026). PN-EN 1484:1999 — Polish version, published 2.09.1999, implements EN 1484:1997 [IDT]; it is not equivalent [NEQ] to the international standard ISO 8245:1987. The standard is current — no withdrawal note. EN 1484:1997 is current in the CEN catalogue, with no newer edition or draft; the second edition of the international standard, ISO 8245:1999, gives the same scope, definitions, principle and reagents in clauses 1–5.
SCOPE (clause 1). Guidance for the determination of organic carbon in drinking water, ground water, surface water, sea water and waste water: definitions, interferences, reagents and sample pretreatment. Organic carbon content 0.3–1000 mg/l; the lower value only in special cases, e.g. drinking water, with instruments capable of measuring such low levels; higher concentrations after dilution. The standard does not deal with instrument-dependent requirements.
DEFINITIONS (clause 3). Total carbon (TC) — organically and inorganically bound carbon, including elemental carbon. Total inorganic carbon (TIC) — elemental carbon, total carbon dioxide, carbon monoxide, cyanide, cyanate and thiocyanate; TOC instruments mostly register as TIC only the CO₂ from hydrogen carbonates and carbonates. TOC — organically bound carbon in dissolved or suspended matter; cyanate, elemental carbon and thiocyanate are also measured. DOC — organic carbon from compounds passing a membrane filter of 0.45 µm pore size. POC — organic carbon that can be purged under the conditions of the method; NPOC — organic carbon that cannot be purged.
INORGANIC CARBON AND VOLATILE SUBSTANCES (clause 1). Before the TOC determination, inorganic carbon is removed by purging the acidified sample with a gas free from CO₂ and organic compounds; alternatively TC and TIC are determined and TOC is calculated from the difference — this is particularly suitable when TIC is less than TOC. Purgeable organic substances such as benzene, toluene, cyclohexane and chloroform may partly escape upon purging — they are then determined separately or the differential method is used; TOC should then be higher than TIC or at least of similar size. Cyanide, cyanate and particles of elemental carbon (soot) are determined together with organic carbon. In the presence of humic material, oxidation by UV radiation may give low values.
TOC IN WATER. TOC measures the carbon content of dissolved and undissolved organic matter in the water, but gives no information on the nature of these substances (introduction of the standard). Surface waters contain much more organic substances than ground waters; 1–75 g C/m³ of TOC has been found in ground waters in Poland.
LEGAL REQUIREMENTS. Water intended for human consumption: TOC “without abnormal change”, with no numerical value (Regulation of the Minister of Health of 22 May 2026, Journal of Laws 2026, item 748, Annex 1 Part C Table 2 item 7); the parameter need not be determined for supplies of less than 10 000 m³ per day (note 6), and oxidizability need not be determined when TOC is analysed (note 9). Measurement uncertainty up to 30 %, estimated at the level of 3 mg/l TOC, using the guidance of PN-EN 1484 (Annex 4 Part B). PN-EN 1484 is the reference method for TOC in waste water (Journal of Laws 2019, item 1311, Annex 12 item 42) and in the monitoring of surface and ground waters (Journal of Laws 2021, item 1576, Annex 8, indicator 3.2.4).
WHAT WE DO NOT GIVE HERE. The available text of the standard ends with the calculation of the result (9.1): we do not give the precision data of the interlaboratory trial, the treatment of samples containing particles or the test report requirements. Parameters of particular analysers (furnace temperature, catalyst, times, detection limits) are not given in the standard — they depend on the instrument and the manufacturer’s instructions.
Method principle
Organic carbon in water is oxidized to carbon dioxide by combustion, by the addition of an appropriate oxidant, by UV radiation or by other high-energy radiation; oxidation by UV radiation with oxygen as the only oxidant is restricted to low-polluted waters with low TOC. Inorganic carbon is removed by acidification and purging or is determined separately. The carbon dioxide formed is determined directly or after reduction, e.g. to methane — by infrared spectrometry, titration (preferably in non-aqueous solution), thermal conductivity, conductometry, coulometry, CO₂-sensitive sensors or flame ionization detection (after reduction of CO₂ to methane) (clause 4).
Applications
- Water intended for human consumption — TOC without abnormal change; not mandatory for supplies below 10 000 m³ per day (Journal of Laws 2026, item 748)
- Waste water — reference method for TOC (Journal of Laws 2019, item 1311, Annex 12)
- Monitoring of surface and ground waters (Journal of Laws 2021, item 1576)
- Drinking water, ground water, surface water, sea water and waste water — TOC and DOC in the range 0.3–1000 mg/l (clause 1)
Key parameters
| Parameter | Value |
|---|---|
| Range | 0.3–1000 mg/l of organic carbon; the lower value only with instruments of adequate sensitivity; higher concentrations after dilution |
| Removal of inorganic carbon | acidification to pH below 2 and purging with a gas free from CO₂ and organic compounds (about 5 min) or the differential method TC − TIC |
| DOC | 0.45 µm membrane filter, previously washed with hot water |
| Calibration | potassium hydrogen phthalate; e.g. for 10–100 mg/l at least 5 solutions |
| Sample storage | at 2–5 °C for up to 7 days; at −15 °C to −20 °C for up to several weeks |
| Result | in mg/l of organic carbon |
Standard
- Standard number
- PN-EN 1484:1999
- Title (PL)
- Analiza wody — Wytyczne oznaczania ogólnego węgla organicznego (OWO) i rozpuszczonego węgla organicznego (RWO)
- Title (EN)
- Water analysis — Guidelines for the determination of total organic carbon (TOC) and dissolved organic carbon (DOC)
Step-by-step procedure
-
Sampling and storage
Representative samples (especially with undissolved substances), without contamination by organic substances, in glass or polyethylene bottles filled completely (EN ISO 5667-3). If biological activity is suspected, acidify to pH 2, e.g. with phosphoric acid — this may lower the result through the loss of volatile substances with the liberated CO₂. If volatile organic compounds are suspected, measure without acidification within 8 h; otherwise store in a refrigerator at 2–5 °C and analyse within 7 days, and if this is not possible — at −15 °C to −20 °C for up to several weeks (7.1).
-
Preparation of the sample
An inhomogeneous sample that cannot be sampled representatively after shaking is homogenized; homogeneity may be checked by analysing the upper and the lower layer. For DOC, the sample is filtered through a 0.45 µm membrane filter previously washed with hot water; the carbon content of the filtrate contributed by the filter is determined and taken into account (7.2).
-
Calibration
According to the manufacturer’s instructions. The calibration curve is established with potassium hydrogen phthalate solutions of adequate concentrations, e.g. for 10–100 mg/l at least 5 solutions: 0 (blank), 1, 2, 3, 5 and 10 ml of stock solution in 100 ml flasks. TOC concentration is plotted against the instrument response; the reciprocal of the slope is the calibration factor f (mg/l). For TIC, calibrate with inorganic carbon solutions; for the differential method TC − TIC, with a known mixture of the organic and inorganic carbon standard solutions. Comparison methods (e.g. IR detection) require calibration; for absolute methods (acidimetry, coulometry) it serves to check the system (8.1).
-
Control
With each series of samples, control solutions are analysed (phthalate, inorganic carbon, substance not readily oxidizable). If deviations exceed the intra-laboratory criteria, check the instrument (oxidation and detection system, leaks, temperature, gas control), changes in the concentration of the control solution and contamination of the system; the whole system and its tightness are checked regularly according to the manufacturer’s instructions (8.2).
-
Determination
According to the manufacturer’s instructions. For direct determination of TOC, inorganic carbon is removed (pH below 2) while minimizing the loss of volatile organic substances; after acidification, pure inert gas free from CO₂ and organic compounds is passed through the system for about 5 min. The concentration must lie within the calibration range (dilute if necessary). Before each batch (e.g. 10 determinations), control experiments are carried out at intervals recommended by the manufacturer or specified by the laboratory (8.3).
-
Calculation
From the calibration curve — normally from peak areas, from peak heights only when they are proportional to the concentration — or from ρ = I · f · V / Vp [mg/l], where I is the instrument response, f the calibration factor (mg/l), V the volume of the diluted sample and Vp the volume of the sample before dilution (9.1).
Required equipment and apparatus
| Equipment | Example | Indicative price |
|---|---|---|
| Organic carbon analyser | any principle of oxidation and CO₂ determination from clause 4; calibration, control and operation according to the manufacturer’s instructions (6.1, 8.1–8.3) | — |
| Homogenization device | e.g. a magnetic stirrer with adequate performance, an ultrasonic apparatus or a high-speed stirrer (6.2) | — |
| Membrane filtration set | 0.45 µm filters washed with hot water — for the determination of DOC (7.2) | — |
| Sample bottles | glass or polyethylene, filled completely (7.1) | — |
| Volumetric flasks, 100 ml and 1000 ml | for the standard and calibration solutions (5.2–5.4, 8.1) | — |
Reagents, media and consumables
| Reagent | CAS | Details |
|---|---|---|
| Dilution water | — | TOC negligibly low compared with the lowest concentration to be determined: for samples below 10 mg/l — at most 0.3 mg/l (0.1 mg/l only for ultrapure water), e.g. UV treatment, condensation; 10–100 mg/l — at most 0.5 mg/l, e.g. double distillation with KMnO₄/K₂Cr₂O₇; above 100 mg/l — at most 1 mg/l, distillation; for TOC below 0.5 mg/l, water for blanks and calibration solutions is prepared immediately before analysis (5.1, Table 1) |
| Potassium hydrogen phthalate, stock solution 1000 mg/l C | 877-24-7 | dissolve 2.125 g of C₈H₅KO₄ (dried for 1 h at 105–120 °C) in 700 ml of water in a 1000 ml flask and make up to the mark; stable for about 2 months in a tightly stoppered bottle in a refrigerator (5.2) |
| Potassium hydrogen phthalate, standard solution 100 mg/l C | — | 100 ml of stock solution to 1000 ml; stable for about one week in a tightly stoppered bottle in a refrigerator (5.3) |
| Standard solution for inorganic carbon, 1000 mg/l C | — | dissolve 4.415 g of sodium carbonate (dried for 1 h at (285 ± 5) °C) in about 500 ml of water in a 1000 ml flask, add 3.500 g of sodium hydrogen carbonate (dried for 2 h over silica gel) and make up to the mark; stable for about 2 weeks at room temperature (5.4) |
| Control solution of a substance not readily oxidizable | — | for checking the operational performance of the system; copper phthalocyanine was used in the interlaboratory trial: 0.256 g of copper phthalocyanine-tetrasulfonic acid tetrasodium salt in 700 ml of water, made up to 1000 ml (100 mg/l C), stable for about 2 weeks; the reagent is toxic (5.5) |
| Non-volatile acid for expelling CO₂ | 7664-38-2 | e.g. phosphoric acid 0.5 mol/l, more concentrated if necessary; the standard solutions may be replaced by other stable titrimetric substances (5.6) |
| Gases | — | air, nitrogen or oxygen free from carbon dioxide and organic impurities; other gases according to the instrument manufacturer’s specifications (5.7) |
Health and safety (OHS)
- Tests according to the standard are carried out by suitably qualified staff (introduction)
- The copper phthalocyanine control solution is toxic (warning at 5.5)
- Instrument, gases and reagents — according to the manufacturer’s instructions and safety data sheets; the standard does not deal with instrument-dependent requirements (clause 1)
Frequently asked questions
Which standard describes this test?
The test is performed according to PN-EN 1484:1999 — “Water analysis — Guidelines for the determination of total organic carbon (TOC) and dissolved organic carbon (DOC)”.
How does this method work?
Organic carbon in water is oxidized to carbon dioxide by combustion, by the addition of an appropriate oxidant, by UV radiation or by other high-energy radiation; oxidation by UV radiation with oxygen as the only oxidant is restricted to low-polluted waters with low TOC. Inorganic carbon is removed by acidification and purging or is determined separately.
What is the measuring range and accuracy?
Range: 0.3–1000 mg/l of organic carbon; the lower value only with instruments of adequate sensitivity; higher concentrations after dilution; Removal of inorganic carbon: acidification to pH below 2 and purging with a gas free from CO₂ and organic compounds (about 5 min) or the differential method TC − TIC; DOC: 0.45 µm membrane filter, previously washed with hot water; Calibration: potassium hydrogen phthalate; e.g. for 10–100 mg/l at least 5 solutions.
How long does the test take?
The procedure comprises 6 steps. The standard does not give a duration for every stage — the laboratory's own procedure decides.
What equipment is required?
Organic carbon analyser, Homogenization device, Membrane filtration set, Sample bottles, Volumetric flasks, 100 ml and 1000 ml.
Where is this test used?
Water intended for human consumption — TOC without abnormal change; not mandatory for supplies below 10 000 m³ per day (Journal of Laws 2026, item 748); Waste water — reference method for TOC (Journal of Laws 2019, item 1311, Annex 12); Monitoring of surface and ground waters (Journal of Laws 2021, item 1576); Drinking water, ground water, surface water, sea water and waste water — TOC and DOC in the range 0.3–1000 mg/l (clause 1).
What safety precautions apply?
Tests according to the standard are carried out by suitably qualified staff (introduction); The copper phthalocyanine control solution is toxic (warning at 5.5); Instrument, gases and reagents — according to the manufacturer’s instructions and safety data sheets; the standard does not deal with instrument-dependent requirements (clause 1).
Which laboratory can perform this test?
The test is performed by laboratories accredited to ISO/IEC 17025. On LabCoda you can find them by the standard number PN-EN 1484.