🌿 Determination of polycyclic aromatic hydrocarbons (PAH) in the gas phase and in particles in stack gases of stationary sources — Soxhlet extraction of filters and sorbents (10 % diethyl ether in n-hexane, about 20 h) with 2- or 6-methylchrysene as recovery standard, extraction of the condensate with n-hexane, concentration, clean-up on a silica gel column and determination by reversed-phase HPLC with fluorescence and UV 229 nm detection or by GC-MS, ISO 11338-2

Environment ISO 11338-2

Overview

WHAT THE STANDARD COVERS. Scope from the text of ISO 11338-2:2003 (Clause 1), in full: “This part of ISO 11338 specifies procedures for sample preparation, clean-up and analysis for the determination of gas and particle-phase polycyclic aromatic hydrocarbons (PAH) in stack and waste gases. The analytical methods are capable of detecting sub-microgram concentrations of PAH per cubic metre of sample, depending on the type of PAH and the flue gas volume sampled. The methods described in this part of ISO 11338 are based on either high performance liquid chromatography (HPLC) or gas chromatography-mass spectrometry (GC-MS). NOTE — ISO 11338-1 describes three methods and specifies minimum requirements for the sampling of PAH in stack and waste gases”. We read the text of the standard in the sample of ISO 11338-2:2003 (first edition, 2003-06-01) from the cover through the table of contents, foreword, introduction and Clauses 1–5 up to and including 6.1.5.2 (the first sentences of HPLC calibration). Outside the sample remain the rest of the calibration and calculation of the HPLC method, the whole GC-MS method (6.2), limitations and interferences (7) and Annexes A–E, including the normative Annex E with the performance characteristics of the HPLC method.

ACCORDING TO THE TEXT OF ISO 11338-2:2003 (foreword, introduction, Clauses 1–6.1.5.2). The standard was prepared by ISO/TC 146 “Air quality”, subcommittee SC 1 “Stationary source emissions”; ISO 11338 has two parts: 1 — sampling, 2 — sample preparation, clean-up and determination. Introduction: PAHs are emitted to the atmosphere primarily by the combustion of fossil fuels and wood and are considered an important class of environmental carcinogens; in stack gases the distribution of PAHs between gas and particle phases depends on temperature, mass and size of emitted particles, humidity, and type and concentration of PAH; during sampling, storage and preparation losses of PAH can occur that prevent quantitative analysis — due to the volatility of two- and three-ring PAHs and the instability of PAHs in the presence of light, O3, NOx, SO2, HCl and certain heavy metals. Reference (2): ISO 4225 (air quality vocabulary). Definitions (3): PAH — compound containing two or more fused aromatic rings made up of carbon and hydrogen atoms; stationary source emission — gas emitted by a stationary plant or process and transported to a chimney; ASE — equipment accelerating extraction by using solvent at elevated temperature (under pressure so that the solvent stays liquid). Principle (4): the sample is taken isokinetically, the particulate phase is collected on a filter and the gas phase by condensation onto an adsorbent (e.g. styrene-divinylbenzene resin XAD-2, polyurethane foam or another of comparable efficiency); parts of the sampling equipment in contact with the sample are washed with solvent, the washings are combined with the filters and adsorbent and extracted in a Soxhlet apparatus (or by another validated method, e.g. ASE); the extract is concentrated on a rotary evaporator and, if necessary, under nitrogen, and cleaned up if necessary; an aliquot is analysed by reversed-phase HPLC or GC-MS; the concentration of each PAH is calculated from the mass of PAH (particle and gas phase) and the volume of gas corrected to reference conditions. Safety (5): all PAHs should be treated as potential carcinogens; contact of PAH in solid form, extract or solution with the body must be prevented; PAHs can co-distil with the solvent and cling to the outside of glassware with ground-glass stoppers; self-preparation of standard solutions is ill-advised — commercial standard solutions (example from the footnote: NIST SRM 1647, a certified solution of 16 PAHs in acetonitrile) minimize the risk of exposure; glassware with PAH solutions must be handled with solvent-resistant gloves; contamination can be revealed by fluorescence under UV light; PAHs in solid form are most dangerous because they become electrostatically charged, so they are weighed in a glove box; unused samples and contaminated equipment, glassware and clothing are disposed of according to regulations. HPLC method — reagents (6.1.2): acetonitrile, n-hexane, methanol and pentane of HPLC grade; diethyl ether preserved with 2 % ethanol; high-purity silica gel type 60, “70 mesh to 23 mesh” (as in the text); anhydrous sodium sulfate heated for at least 4 h at 300 °C; recovery standard — 2-methylchrysene or 6-methylchrysene of purity at least 98 %; helium for degassing the mobile phase and nitrogen for concentration; aluminium foil; glass wool. Apparatus (6.1.3): Soxhlet apparatus 100–200 ml; glass-fibre filters precleaned for 3 h at 200 °C or to an acceptable blank level; round-bottom flasks; rotary evaporator (vacuum up to 0,1 MPa, bath up to 50 °C); Kuderna-Danish concentrators 500 ml with Snyder column; nitrogen blow-down concentrator with flow control and water bath; separation funnels 100 and 250 ml; glass chromatography column; 10 ml conical tubes; extraction thimbles pre-extracted with methanol; refrigerator below 4 °C or freezer below −15 °C; oven up to 500 °C; HPLC system with gradient pumps, injector up to 20 µl, column thermostat in the range 29–40 °C ± 1 °C, fluorescence detector with programmable excitation and emission wavelengths and UV detector at 229 nm; glass or stainless steel column 20–250 mm, internal diameter 3–4,6 mm, C18 phase with 3–5 µm particles; guard column (always recommended, because sample and eluent contamination raises pressure and alters selectivity); degassing of eluents with helium (to avoid quenching of fluorescence); syringes 10–1000 µl. Storage (6.1.4.1): sample parts in sealed containers, protected from light, at 0–4 °C (extraction within one week of completion of sampling) or at −15 °C or below (extraction within one month); the condensate is acidified with hydrochloric acid to pH ≈ 2 and may be stored up to 14 days. Extraction of filters and sorbents (6.1.4.2): filter and sorbent in a Soxhlet thimble; immediately before extraction 500 µl of recovery standard in acetonitrile (about 1 µg/ml) is added — for separate analysis of sorbent and filter to both; extraction with 10 % diethyl ether in n-hexane for about 20 h at 4 cycles per hour; the recovery standard is added to all samples, including field and method blanks; other extraction techniques (e.g. ASE) and solvents — after validation by the user. Extraction of condensate (6.1.4.3): the condensate and the n-hexane rinsings of the impingers are shaken in a separation funnel for at least 5 min, the extraction is repeated, the n-hexane fractions are combined and dried over sodium sulfate; the volume of n-hexane in each of the two extractions — at least 20 % of the condensate volume. Concentration (6.1.4.4): the combined extracts are filtered through a precleaned glass-fibre filter, concentrated on the evaporator to about 2 ml, transferred with n-hexane to a 10 ml tube, 1 ml of acetonitrile is added and in a 25 °C water bath under a gentle stream of nitrogen the hexane and a small part of the acetonitrile are evaporated, after which the volume is adjusted to 1,0 ml with acetonitrile; the extract is stored in sealed brown vials below 4 °C, protected from light, and analysed within 30 days; evaporator — at about 0,1 MPa and a bath not warmer than 45 °C; if the extract has been evaporated to dryness, substantial losses of PAH may occur and the sample should be discarded (note 1 — concentration to 1 ml may not be needed, depending on the target detection limit, detector sensitivity and sampled gas volume; note 2 — the final nitrogen evaporation is the most critical step: losses of volatile two- to four-ring PAHs reach 10 % with n-hexane as extraction solvent, and 10–40 % with toluene). Clean-up (6.1.4.5): may not be necessary for relatively clean matrices, in complex ones it eliminates interferences from polar and non-polar compounds; an extract in dichloromethane is solvent-exchanged to n-hexane before clean-up; the silica gel is extracted for 6 h with dichloromethane in a Soxhlet apparatus and activated for 16 h at 450 °C; a 15–25 ml column (e.g. 160 mm × 11,5 mm) is packed with 10 g of gel in pentane and 1 g of sodium sulfate; after pre-elution with 40 ml of pentane, 1 ml of extract in n-hexane and 2 ml of n-hexane are applied, 25 ml of pentane is eluted (the fraction may be discarded; it contains aliphatic hydrocarbons), and the PAHs — with 25 ml of dichloromethane in pentane (4:6) at 2 ml/min; the eluate is concentrated, solvent-exchanged to acetonitrile and adjusted to 1,0 ml; commercial clean-up columns — after validation (note — an additional elution with 25 ml of methanol elutes polar compounds, e.g. oxygenated, nitrated and sulfonated PAH). HPLC analysis (6.1.5.1): typical parameters — column 200 mm × 4,6 mm, C18, 5 µm; mobile phase A — acetonitrile/water (50 % volume fraction), B — acetonitrile; linear gradient from 100 % A to 100 % B; flow 0,8 ml/min; injection 20 µl; column temperature (29 ± 1) °C; fluorescence detector with programmable wavelengths for more selectivity in complex matrices (example in Annex A); acenaphthylene is determined by the UV detector at 229 nm because it does not fluoresce; a column length of at least 20 cm is desirable; injection volumes of 100 µl or more, columns of 15 cm or less and gradients of 25 min or less should be avoided — typical gradient time is 40–60 min (note 2 — diode-array detectors improve selectivity and help to identify false positives). Calibration (6.1.5.2): standards of individual PAHs at a minimum of five concentration levels, the lowest near the quantification limit.

STATUS (as of 03.10.2026). The standard has not been adopted as a PN: the PKN search engine with the queries “ISO 11338-2”, “PN-EN ISO 11338-2” and “11338” (03.10.2026) returns no card. International document: ISO 11338-2:2003 (published 11-06-2003) has the status “Published” in the iTeh catalogue, stage 90.93 — standard confirmed (review from 18-03-2026, completed 29-08-2026); the Slovenian SIST ISO 11338-2:2004 — “Published” (read 03.10.2026).

HOW MANY LABORATORIES AND IN WHAT FORM (copy of the accreditation scope database, data up to 17.09.2026, read 03.10.2026). The number 11338-2 appears in 15 records at 6 laboratories in Poland: AB 213, AB 300, AB 412, AB 550, AB 746, AB 886. In the current scopes on the PCA website (read 03.10.2026, issues from 12.02.2026 to 22.09.2026) five laboratories give “ISO 11338-2:2003”, and AB 412 — “ISO 11338-2” without year, together with procedure WKJ-4/IB/129, in the flexible scope of accreditation (mark E). AB 746 and AB 886 also have sampling according to ISO 11338-1:2003 (AB 886 — method B). Both AB 746 items with this standard are set in bold italics with an asterisk in the PCA document — accreditation suspended at the laboratory’s request from 17.04.2026 to 16.10.2026; the items of the other five laboratories are not suspended. The “Laboratories” tab (“ISO 11338-2”) shows 9 laboratories — 6 from Poland and 3 from the Czech Republic (CZ 1012, CZ 1163, CZ 1350); checked with the tab query on the production server labcoda.pl on 03.10.2026.

WHAT THE LABORATORIES TEST (items in PCA scopes). “Content” or “Concentration/content” of PAH in stack gas samples collected on filters and sorbent tubes (AB 213, AB 412, AB 550), on a filter and adsorbers (AB 300), on a filter, sorbent and into an absorbing solution (AB 746), and in stack gases (AB 886); AB 746 also PAH concentration in waste gas cleaning installations and PAH reduction efficiency (calculated). Technique: HPLC with fluorescence detection (AB 213, AB 412, AB 746), HPLC-FLD and HPLC with UV detection (AB 300, AB 886), UHPLC with fluorescence detection (AB 550); no laboratory gives GC-MS. Ranges: (0,050–5,0) µg per sample for 15 PAHs (AB 213), (0,4–4,0) µg per sample for 15 PAHs (AB 300), (0,000005–0,005) mg per sample for 5 PAHs — benzo(a)pyrene, benzo(b)- and benzo(k)fluoranthene, indeno(1,2,3-cd)pyrene and fluoranthene (AB 550), (0,00005–1) mg/m³ and (0,050–5,0) µg per sample (AB 746), for individual PAHs separately on filters and tubes (0,00001–1,000) to (0,00003–1,000) mg/m³ and from (0,01–22) to (0,03–27) µg per sample (AB 886). Sum of PAH (calculated) is given by AB 213, AB 550, AB 746 and AB 886, PAH emission (calculated) — by AB 746 and AB 886. Sampling according to ISO 11338-1 has a separate entry in the Knowledge Base.

WHERE A SEEMINGLY CORRECT RESULT IS EASY TO GET. Acenaphthylene: it is determined with the UV detector at 229 nm because it does not fluoresce (6.1.5.1) — an acenaphthylene result from the fluorescence detector alone does not follow from this standard; HPLC-UV next to fluorescence detection is given in PCA scopes by AB 300 and AB 886. Column: the standard gives columns of 20–250 mm with 3–5 µm particles and says to avoid columns of 15 cm or less, gradients of 25 min or less and injections of 100 µl or more (6.1.3.15, 6.1.5.1) — UHPLC conditions (AB 550) are not described in the sample. Storage: samples at 0–4 °C must be extracted within a week, at −15 °C or below — within a month, acidified condensate within 14 days, and extracts analysed within 30 days (6.1.4.1, 6.1.4.4). Concentration: the extract must not be evaporated to dryness — such a sample is discarded; the final nitrogen evaporation causes losses of volatile two- to four-ring PAHs of up to 10 % with n-hexane and 10–40 % with toluene (6.1.4.4, note 2). Recovery: the recovery standard (2- or 6-methylchrysene) is added to every sample, including blanks, immediately before extraction, and for separate analysis — to both filter and sorbent (6.1.4.2). Phases: the concentration is calculated from the sum of the PAH mass in the particle and gas phases (filter, sorbent, condensate and washings) and the gas volume corrected to reference conditions (4.2) — a result from the filter alone or the sorbent alone is not a concentration in the stack gas. Calibration: at least five levels, the lowest near the quantification limit (6.1.5.2). Reagents: a solvent or extraction technique other than 10 % diethyl ether in n-hexane in a Soxhlet apparatus must be validated (6.1.4.2).

WHAT WE DO NOT GIVE. We do not have the rest of 6.1.5.2 and the calculation of the HPLC method, the GC-MS method (6.2), limitations and interferences (7) or Annexes A–E — so we give no excitation and emission wavelengths, characteristic ions and internal standards for GC-MS, detection and quantification limits or performance characteristics of the HPLC method from Annex E.

Method principle

The filter and sorbent from a stack gas sample are extracted in a Soxhlet apparatus after adding a recovery standard, and the condensate with n-hexane; the combined extracts are concentrated, cleaned up on a silica gel column if necessary and transferred to acetonitrile; PAHs are separated by reversed-phase HPLC and detected with a fluorescence detector (acenaphthylene — UV 229 nm) or determined by GC-MS, and the concentration in the gas is calculated from the sum of masses in the particle and gas phases and the sampled gas volume.

Applications

• Stack and waste gases of stationary sources — PAH in the gas phase and in particles, samples from filters, sorbents and condensate taken according to ISO 11338-1; 6 laboratories in PCA scopes in Poland
• Waste gas cleaning installations — PAH concentration and PAH reduction efficiency (calculated) — in the PCA scope of one laboratory (item suspended on request until 16.10.2026)
• Sum of PAH and PAH emission (calculated) together with sampling according to ISO 11338-1

Key parameters

Standard

Standard number

ISO 11338-2:2003

Title (PL)

Emisja ze źródeł stacjonarnych — Oznaczanie wielopierścieniowych węglowodorów aromatycznych w fazie gazowej i w cząstkach — Część 2: Przygotowanie próbek, oczyszczanie i oznaczanie (tłumaczenie tytułu nasze; normy nie wprowadzono do PN)

Title (EN)

Stationary source emissions — Determination of gas and particle-phase polycyclic aromatic hydrocarbons — Part 2: Sample preparation, clean-up and determination

Step-by-step procedure

1. Storage

   Sample parts sealed, in the dark, at 0–4 °C (extraction within a week) or ≤ −15 °C (within a month); acidify the condensate with HCl to pH ≈ 2. ISO 11338-2:2003 current (confirmed 29-08-2026, iTeh; not adopted as a PN).

2. Extraction of filter and sorbent

   Add 500 µl of recovery standard (2- or 6-methylchrysene) and extract in a Soxhlet apparatus with 10 % diethyl ether in n-hexane for about 20 h, 4 cycles/h.

3. Extraction of condensate

   Shake twice with n-hexane (≥ 20 % of the condensate volume, ≥ 5 min), combine the fractions and dry over sodium sulfate.

4. Concentration

   Combine and filter the extracts, concentrate on the evaporator to about 2 ml, add 1 ml of acetonitrile, remove the hexane under nitrogen at 25 °C and adjust to 1,0 ml; do not evaporate to dryness.

5. Clean-up

   In complex matrices — column with 10 g of silica gel: 40 ml of pentane, extract, 25 ml of pentane, PAHs with 25 ml CH2Cl2/pentane 4:6; concentrate and transfer to 1,0 ml of acetonitrile.

6. Determination

   HPLC C18 with acetonitrile/water gradient, fluorescence detector (acenaphthylene — UV 229 nm), calibration at ≥ 5 levels; or GC-MS (6.2, outside the sample).

7. Result

   Concentration of each PAH from the sum of masses in the particle and gas phases and the gas volume corrected to reference conditions.

Required equipment and apparatus

Reagents, media and consumables

Health and safety (OHS)

• All PAHs should be treated as potential carcinogens; body contact with PAH in solid form, extract or solution must be prevented, and glassware with solutions handled with solvent-resistant gloves (5)
• Instead of preparing standard solutions from solid PAH (which become electrostatically charged), commercial solutions are recommended; solid PAHs are weighed in a glove box, and contamination is revealed under UV light (5)
• Unused samples and contaminated equipment, glassware and clothing are disposed of according to regulations (5)

Frequently asked questions