🧬 THM / Trihalomethanes in Water
In short
Determination of highly volatile halogenated hydrocarbons, including trihalomethanes (chloroform, bromodichloromethane, dibromochloromethane, bromoform), by gas chromatography with an electron-capture detector or another suitable detector — after liquid–liquid extraction with pentane or by static headspace analysis. The test is performed according to PN-EN ISO 10301:2002; Methods: liquid/liquid extraction (section 2) and static headspace analysis (section 3). The procedure comprises 8 steps; it is used for: Drinking water — total trihalomethanes 100 µg/l (Journal of Laws 2026, item 748, Annex 1 Part B item 31), Swimming pool water, groundwater, rivers and lakes — liquid/liquid extraction (1.1), Waste water — reference methodology for trichloromethane, tetrachloromethane, trichloroethylene, tetrachloroethylene and 1,2-dichloroethane (Journal of Laws 2019, item 1311, Annex 12).
At a glance
- Standard: PN-EN ISO 10301:2002
- Category: Physicochemistry
- Procedure steps: 8
- Methods: liquid/liquid extraction (section 2) and static headspace analysis (section 3)
- Typical quantification limits — extraction: chloroform 0.05–0.3 µg/l; tribromomethane 0.1 µg/l (Table 1)
- Typical quantification limits — headspace: chloroform 0.3; bromodichloromethane 0.2; dibromochloromethane 0.3; bromoform 5 µg/l (Table 2)
Overview
STATUS (as of 29.10.2026). PN-EN ISO 10301:2002 — Polish version, published 16.12.2002, implements EN ISO 10301:1997 and ISO 10301:1997 [IDT]; it replaced PN-EN ISO 10301:2002 (English version). The standard is current — no withdrawal note. ISO 10301:1997 (first edition, 10.04.1997) — no newer edition.
SCOPE (1.1, Tables 1–2). Two gas chromatographic methods. Section 2 — liquid/liquid extraction: drinking water, groundwater, swimming pool water, most rivers and lakes and many sewage and industrial effluents. Section 3 — static headspace analysis: drinking water, surface water and groundwater; in practice also industrial effluents as a screening method, sometimes with confirmation of the result by the extraction method. The standard does not cover purge and trap (stripping with gas and trapping on an adsorbent). Typical quantification limits for trihalomethanes: liquid/liquid extraction — chloroform 0.05–0.3 µg/l, tribromomethane 0.1 µg/l; headspace — chloroform 0.3 µg/l, bromodichloromethane 0.2 µg/l, dibromochloromethane 0.3 µg/l, tribromomethane (bromoform) 5 µg/l.
DEFINITION AND INTRODUCTION (1.3.1, introduction). Highly volatile halogenated hydrocarbons are fluorinated, chlorinated, brominated and/or iodinated mainly non-aromatic hydrocarbons with 1–6 carbon atoms, generally boiling at 20–220 °C. They are used in industry, commerce and households; they reach waters with waste water and can contaminate drinking water, and they are also formed when chlorine is used as an oxidizing agent in water and waste water treatment. In uncontaminated groundwater and rainwater their concentrations are generally below 0.1 µg/l.
LEGAL REQUIREMENTS. Drinking water: total trihalomethanes — 100 µg/l, the sum of trichloromethane (chloroform), tribromomethane (bromoform), dibromochloromethane and bromodichloromethane; where possible, without compromising disinfection, a lower value should be strived for (Journal of Laws 2026, item 748, Annex 1 Part B item 31). Measurement uncertainty 40 % for total trihalomethanes and for chloroform; for the sum, the requirement applies to individual compounds at 25 % of the parametric value (Annex 4 Part B items 48–49, explanatory note 7). Waste water: PN-EN ISO 10301 is a reference methodology among others for trichloromethane (chloroform) — detection limit 0.1 µg/l at concentrations below 0.5 mg/l (sensitive detector), accuracy and precision ± 50 % at a concentration equal to twice the detection limit (Journal of Laws 2019, item 1311, Annex 12 item 66); also for tetrachloromethane, trichloroethylene, tetrachloroethylene and 1,2-dichloroethane (items 63, 65, 62, 24). Monitoring of surface water and groundwater: GC methodology for indicator 4.1.32 “Trichloromethane” (Journal of Laws 2021, item 1576, Annex 8).
WHAT WE DO NOT GIVE HERE. The publicly available text of the standard ends with 2.6.2 (septum-vial extraction). We do not give the rest of the extraction procedure, the gas chromatographic analysis (2.6.3), the blank determinations (2.6.4), the calibration and calculation or the whole of section 3 (conditions of the headspace analysis); the informative annexes contain, among others, examples of chromatograms, data on the sensitivity of the electron-capture detector and recoveries for pentane extraction (PKN catalogue card).
Method principle
Section 2 (2.1, 2.3.3, 2.4.1): the highly volatile halogenated hydrocarbons are extracted from the sample with an organic solvent — pentane, and if the compound of interest elutes together with it, another solvent (hexane, petroleum ether, heptane, xylene for waste waters) — and the extract is analysed by a gas chromatograph with an electron-capture detector or another suitable detector. The separation requires high separating power and is best achieved on capillary columns: with a nonpolar phase (poly(dimethylsiloxane)) or a semipolar phase (poly(5 % diphenyl-, 95 % dimethylsiloxane)), with a phase ratio of about 80–100 and a length generally of more than 30 m.
Section 3: static headspace analysis — procedure outside the available text of the standard.
Applications
- Drinking water — total trihalomethanes 100 µg/l (Journal of Laws 2026, item 748, Annex 1 Part B item 31)
- Swimming pool water, groundwater, rivers and lakes — liquid/liquid extraction (1.1)
- Waste water — reference methodology for trichloromethane, tetrachloromethane, trichloroethylene, tetrachloroethylene and 1,2-dichloroethane (Journal of Laws 2019, item 1311, Annex 12)
- Monitoring of surface water and groundwater — indicator 4.1.32 “Trichloromethane” (Journal of Laws 2021, item 1576, Annex 8)
- Industrial effluents — headspace analysis as a screening method (1.1)
Key parameters
| Parameter | Value |
|---|---|
| Methods | liquid/liquid extraction (section 2) and static headspace analysis (section 3) |
| Typical quantification limits — extraction | chloroform 0.05–0.3 µg/l; tribromomethane 0.1 µg/l (Table 1) |
| Typical quantification limits — headspace | chloroform 0.3; bromodichloromethane 0.2; dibromochloromethane 0.3; bromoform 5 µg/l (Table 2) |
| Extraction | about 200 ml of sample, pentane — 10 ml for drinking water, 50 ml for waste water; 5 min of vigorous mixing (2.6.1) |
| Detector | electron-capture (ECD) or another suitable detector (2.1) |
| Storage | samples at about 4 °C, extraction within 48 h if possible; extract at about 4 °C for no longer than one month (2.5, 2.6.1) |
Standard
- Standard number
- PN-EN ISO 10301:2002
- Title (PL)
- Jakość wody — Oznaczanie łatwo lotnych chlorowcowych pochodnych węglowodorów — Metody z zastosowaniem chromatografii gazowej
- Title (EN)
- Water quality — Determination of highly volatile halogenated hydrocarbons — Gas chromatographic methods
Step-by-step procedure
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Sampling
According to ISO 5667-1 and ISO 5667-2, into bottles prepared according to 2.4.2; fill the bottle completely, discard the water, refill and stopper so as to leave no headspace — slowly, until it overflows, avoiding turbulence; keep the use of plastics tubing to a minimum (2.5).
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Free halogens
If the reaction of free halogens with organic matter (formation of trihalomethanes) is to be eliminated, add an excess of sodium thiosulfate to the bottle after rinsing it but before sampling — normally 0.1–0.2 ml of the 30 g/l solution or 3–5 mg of the solid for about 250 ml of sample (2.5).
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Transport and storage
Avoid warming the samples during transport; if storage is unavoidable — cool to about 4 °C and extract within 48 h if possible, because the extracts are much more stable than the samples (2.5).
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Extraction
Discard enough water from the full bottle to leave (200 ± 10) ml, weigh the bottle with the sample, add pentane (10 ml for drinking water, 50 ml for waste water), stopper and mix vigorously for 5 min with a magnetic stirrer or a mechanical shaker (2.6.1).
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Phase separation
After the layers have separated, draw off the upper solvent layer with a pipette or with a microseparator with glass wool (adding water through the side tube until the extract passes the glass wool); if separation is poor — centrifugation of a few millilitres in a closed vessel or freezing (2.6.1).
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Extract
Do not concentrate by evaporation; analyse immediately, and if this is not possible — store in an airtight bottle at about 4 °C for no longer than a month (2.6.1).
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Contamination and blanks
Carry out the extraction in an environment as free as possible from volatile halogenated compounds (sprays, solvents, refrigerants); blank determinations are necessary (2.6.1).
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Chromatographic analysis
Analyse the extract by a gas chromatograph with an electron-capture detector (2.6.3 — details outside the available text); for comparison with the regulation the four trihalomethanes are summed.
Required equipment and apparatus
| Equipment | Example | Indicative price |
|---|---|---|
| Gas chromatograph | with an electron-capture detector or another suitable detector and a capillary column: nonpolar or semipolar phase, phase ratio about 80–100, length generally more than 30 m (2.4.1) | — |
| Glass bottles of about 250 ml with a solid glass stopper | heated upside down together with the stoppers for at least 1 h at 150 °C before use (2.4.3) | — |
| Glass vials of 30–40 ml with a PTFE-coated septum | for septum-vial extraction (2.4.4, 2.6.2) | — |
| Magnetic stirrer or mechanical shaker | with PTFE-coated stirrer rods of about 4 cm, stored separately for each concentration range (2.4.5–2.4.6) | — |
| Microseparator, glass wool and bottles for the extract | glass wool washed with the extraction solvent; bottles of about 2 ml with a PTFE-coated septum (2.4.7–2.4.9) | — |
Reagents, media and consumables
| Reagent | CAS | Details |
|---|---|---|
| Water for calibration solutions and the blank | — | checked for the compounds of interest; contaminated water is purified: heating to about 60 °C, passing clean nitrogen (about 150–200 ml/min) through it for 1 h, cooling, storage in a glass bottle in the dark (2.3.1) |
| Gases for chromatography | — | ultrapure nitrogen (at least 99.996 % by volume) or an ultrapure argon–methane mixture; other gases according to the instrument manufacturer (2.3.2) |
| Pentane | 109-66-0 | extraction solvent free from highly volatile chlorinated hydrocarbons — checked by gas chromatography with an electron-capture detector (2.3.3) |
| Sodium sulfate, anhydrous | 7757-82-6 | heat a portion of 250–300 g (4 h ± 30 min) at (500 ± 20) °C, cool to about 200 °C in the furnace, then in a desiccator (2.3.4) |
| Sodium thiosulfate | 10102-17-7 | solution 30 g/l: (46 ± 0.2) g of Na₂S₂O₃·5H₂O in (1000 ± 5) ml of water; the solid form may be used (2.3.5) |
| Reference substances and standard solutions | — | pure substances; stock solutions by adding with a syringe under the surface of a solvent (e.g. 50 mg in 100 ml — stable for about a year), intermediate e.g. 10 µg/ml in the extraction solvent (6 months), working solutions at least five concentrations in the ng/ml range (at least a month); all at about 4 °C in the dark (2.3.8–2.3.11) |
Health and safety (OHS)
- Pentane, solvents and standards of halogenated hydrocarbons are handled according to the safety data sheets
- The electron-capture detector with a ⁶³Ni radiation source (textbook “Chemia wody”, Wrocław University of Science and Technology, section 6.4.1) is operated according to the manufacturer’s instructions
Frequently asked questions
Which standard describes this test?
The test is performed according to PN-EN ISO 10301:2002 — “Water quality — Determination of highly volatile halogenated hydrocarbons — Gas chromatographic methods”.
How does this method work?
Section 2 (2.1, 2.
What is the measuring range and accuracy?
Methods: liquid/liquid extraction (section 2) and static headspace analysis (section 3); Typical quantification limits — extraction: chloroform 0.05–0.3 µg/l; tribromomethane 0.1 µg/l (Table 1); Typical quantification limits — headspace: chloroform 0.3; bromodichloromethane 0.2; dibromochloromethane 0.3; bromoform 5 µg/l (Table 2); Extraction: about 200 ml of sample, pentane — 10 ml for drinking water, 50 ml for waste water; 5 min of vigorous mixing (2.6.1).
How long does the test take?
The procedure comprises 8 steps. The standard does not give a duration for every stage — the laboratory's own procedure decides.
What equipment is required?
Gas chromatograph, Glass bottles of about 250 ml with a solid glass stopper, Glass vials of 30–40 ml with a PTFE-coated septum, Magnetic stirrer or mechanical shaker, Microseparator, glass wool and bottles for the extract.
Where is this test used?
Drinking water — total trihalomethanes 100 µg/l (Journal of Laws 2026, item 748, Annex 1 Part B item 31); Swimming pool water, groundwater, rivers and lakes — liquid/liquid extraction (1.1); Waste water — reference methodology for trichloromethane, tetrachloromethane, trichloroethylene, tetrachloroethylene and 1,2-dichloroethane (Journal of Laws 2019, item 1311, Annex 12); Monitoring of surface water and groundwater — indicator 4.1.32 “Trichloromethane” (Journal of Laws 2021, item 1576, Annex 8); Industrial effluents — headspace analysis as a screening method (1.1).
What safety precautions apply?
Pentane, solvents and standards of halogenated hydrocarbons are handled according to the safety data sheets; The electron-capture detector with a ⁶³Ni radiation source (textbook “Chemia wody”, Wrocław University of Science and Technology, section 6.4.1) is operated according to the manufacturer’s instructions.
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 ISO 10301.