🌿 Pentane in workplace air — gas chromatography, PN-Z-04318

Environment PN-Z-04318

Overview

WHAT THIS STANDARD DESCRIBES. The scope from the PKN catalogue card: "Podano metodę polegającą na adsorpcji par pentanu na węglu aktywnym, desorpcji związku disiarczkiem węgla i analizie otrzymanego roztworu metodą chromatografii gazowej. Najmniejsze stężenie pentanu, jakie można oznaczyć tą metodą wynosi 450 mg/m3" [A method is given consisting in the adsorption of pentane vapours on activated carbon, desorption of the compound with carbon disulphide and analysis of the resulting solution by gas chromatography. The lowest concentration of pentane that can be determined by this method is 450 mg/m3]. The standard was published on 27 June 2005 in a Polish-language version, has seven pages and is maintained by KT 159. The card has no "Replaces" field — it is a document without a predecessor in the PN collection. The card has neither a "Withdrawn" header nor a "Withdrawal date" row (checked on 23.09.2026).

A LIMIT OF QUANTIFICATION BELOW THE REQUIREMENT — SOMETHING THAT HAS TO BE CALLED BY ITS NAME. The limit value for pentane is **NDS 3000 mg/m³** (item 457 of the list in the wording given by the regulation of 26 March 2026, Journal of Laws 2026 item 447; the list sets NO short-term NDSCh value for pentane). The lowest determinable concentration is 450 mg/m³, i.e. **0.15 of the limit value — one seventh, not one tenth**. PN-EN 482 requires a measurement procedure to cover the range from 0.1 to 2.0 of the limit value; this method only starts at 0.15. **It therefore misses the requirement by a factor of one and a half.** The method for sulphur dioxide (PN-Z-04015-12, a separate entry in this database), where the lowest determinable concentration is one quarter of the limit value, does not meet this requirement either.

WHAT THIS MEANS FOR THE LABORATORY. With this method a result "below the limit of quantification" means "below 450 mg/m³", i.e. below 15 % of the limit value — and not below 10 %, as with methods that meet the requirement. For the assessment of exposure this is sufficient, because a concentration below 15 % of the NDS is safe exposure within the meaning of PN-Z-04008-7. But for **demonstrating compliance with the one-tenth threshold**, on which the regulation of the Minister of Health makes the frequency of periodic measurements depend, this method is not sufficient: the employer cannot demonstrate on its basis that the concentration does not exceed 0.1 NDS, because the method does not see that level. The laboratory should state this in the report instead of giving only the limit of quantification.

WHY THIS PARTICULAR METHOD FARES WORSE. The cause lies in the substance itself, not in the procedure. Pentane is a hydrocarbon with a very high vapour pressure (boiling point 36 °C), so it is poorly retained on activated carbon and easily escapes from it when the sample is stored — the permissible volume of air is therefore limited, and with it the limit of quantification. For comparison, acetic acid (PN-Z-04323, a separate entry in this database), also determined chromatographically, has a fivefold margin over the requirement: it is less volatile and is retained on silica gel permanently.

NO TRANSITIONAL PROVISION — CHECKED ON THE TEXT OF THE ACT. § 2 of the amending regulation does not mention pentane; the value of 3000 mg/m³ applies directly.

SCALE OF CITATIONS (reading of 23.09.2026, copy of the database of accreditation scopes). Matching by the BEGINNING of the notation: 33 entries at 19 laboratories; across all forms of the core "04318" — the same. Four forms of notation, the balance of occurrences agrees: "PN-Z-04318:2005" 30 times and three notations with an addition — the number of an own instruction ("IN-59 wyd. 3 z dnia 18.12.20…"), the number of a procedure ("PB_42 edycja 5 z dnia 2022-0…") and the exclusion of a clause ("z wył. pkt.8" [z wył. pkt. = excluding clause]).

THE RATIO OF ENTRIES TO LABORATORIES IS 1.7 — AND IT SAYS SOMETHING ABOUT HOW THE SCOPE IS WRITTEN OUT. For the other seven standards it is close to one: one laboratory, one row. Here some laboratories split pentane into two or three rows, because the determination is usually carried out together with other aliphatic hydrocarbons from the same sorbent tube — hexane, heptane, octane — and each of them is often a separate scope entry under the same standard.

THE NOTATION "Z WYŁ. PKT.8" — I.E. THE THIRD FORM OF ABBREVIATION FOR THE SAME WORD. In accreditation scopes the exclusion of a clause of a standard is written in three ways: with the full words "z wyłączeniem punktu" [excluding clause], with the abbreviation "z wył. pkt." and with "pkt" alone followed by a number. A pattern searching for the full words loses the other two forms — this is the same class as ONE FORM OF AN ABBREVIATION from our list of routes to a false number, visible here in one of thirty-three notations.

Method principle

Air from the workplace is drawn through a tube with activated carbon, on which the pentane vapours are adsorbed. After sampling, the analyte is desorbed with carbon disulphide, and the resulting solution is analysed by gas chromatography with flame ionisation detection. Carbon disulphide is the solvent of choice here because it gives a negligible signal in the FID and does not mask the hydrocarbon peak. The concentration in air is calculated from the mass of pentane in the solution and the volume of air drawn, taking into account the recovery factor from the sorbent.

Applications

• Periodic measurements of occupational exposure required by the regulation of the Minister of Health on tests and measurements of agents harmful to health in the working environment
• Production and processing of foamed plastics — pentane as a blowing agent in expanded polystyrene
• Refineries, fuel depots and petroleum laboratories — pentane as a component of light fractions
• Solvent extraction workplaces and adhesive production

Key parameters

Standard

Standard number

PN-Z-04318:2005 (wersja polska)

Title (PL)

Ochrona czystości powietrza -- Oznaczanie pentanu na stanowiskach pracy metodą chromatografii gazowej

Title (EN)

Air purity protection — Determination of pentane at workplaces by gas chromatography

Step-by-step procedure

1. Sampling

   Draw the volume of air provided for in the procedure through a tube with activated carbon; for pentane the volume is limited because of sorbent breakthrough.

2. Storage

   Close the tube tightly and store it under the conditions provided for in the procedure — pentane escapes from the sorbent when stored at room temperature.

3. Desorption

   Desorb the analyte with carbon disulphide in a tightly closed vial.

4. Analysis

   Analyse the solution after desorption by gas chromatography with FID detection; read the concentration from the calibration curve.

5. Calculation

   Calculate the concentration of pentane in air from the mass in the solution, the volume of air drawn and the recovery factor.

6. Reference to the limit value and reservation

   Compare the exposure index with the NDS of 3000 mg/m³. State in the report that the limit of quantification of the method is 0.15 of the limit value — a result "below the limit of quantification" DOES NOT demonstrate compliance with the threshold of one tenth of the NDS.

Required equipment and apparatus

Reagents, media and consumables

Health and safety (OHS)

• Carbon disulphide is highly toxic, flammable and has a very low flash point — work only in a properly functioning fume hood, away from sources of ignition
• Pentane is extremely flammable; explosion hazard zones apply at workplaces with pentane
• Store the sorbent tubes tightly closed after sampling — loss of analyte lowers the result rather than raising it, so the error goes in the direction that is dangerous for the worker

Frequently asked questions