BS 6069-3.4:1991

Committees responsible
National foreword
Method
1. Scope
2. Normative references
3. Principle
4. Reagents
5. Apparatus
6. Sampling
7. Procedure
8. Expression of results
9. Test report
Annexes
A. Determination of breakthrough volume
B. Determination of desorption efficiency
C. Chromatographic columns suitable for use for the
    analysis of aromatic hydrocarbon solvent vapours
D. Bibliography
Tables
1. Sample size and sampling rate
2. Optimum sampling rate during 8 h as a function of
    the relative humidity and the presence of light
    hydrocarbons
B.1 Desorption efficiency data
C.1 Retention data for aromatic hydrocarbon solvents and
    carbon disulfide on SE 30 and C20M relative to
    toluene

Applicable to a variety of aromatic hydrocarbons in the range 1 mg/m³ to 1000 mg/m³ when sampling 10 litres of air.

This International Standard specifies a charcoal tube/gas chromatographic method for the determination of the concentration of vaporous aromatic hydrocarbons in workplace air.

The method is valid for the measurement of the concentrations of airborne vapours of any of the following compounds:

1. benzene;
2. toluene;
3. ethylbenzene;
4. m-xylene;
5. o-xylene;
6. p-xylene;
7. styrene (vinylbenzene);
8. cumene (isopropylbenzene);
9. 1,2,3-trimethylbenzene;
10. 1,2,4-trimethylbenzene;
11. 1,3,5-trimethylbenzene;
12. 4-tert-butyltoluene;
13. 3-methylstyrene;
14. 4-methylstyrene;
15. isopropenylbenzene.

The method is valid for concentrations of airborne vapours of these compounds in the range from approximately 1 mg/m³ to 1 000 mg/m³ (about 0,2 ml/m³ to 200 ml/m³; see 8.1) when sampling 10 litres of air.

NOTE 1 The upper limit of the useful range is set by the adsorptive capacity of the first section of the charcoal tube (5.1) used. This capacity is measured as a breakthrough volume of air, which should not be exceeded during sampling (see clause 6 and Annex A).

The lower limit is set by a number of parameters, including the noise level of the detector (5.9), blank concentrations due to the contamination of the charcoal and carbon disulfide by the substance analysed, desorption efficiency (see Annex B) and interference of the solvent peak in the gas chromatographic analysis.

The method is also valid for the measurement of airborne concentrations of mixtures of these compounds. In such cases, the unique properties of each compound have to be considered when determining the volume of air to be sampled and the gas chromatographic conditions to be used. The method may be applicable for other substituted monocyclic aromatic hydrocarbons, but its validity has to be tested.

NOTE 2 When analysing aromatic hydrocarbon mixtures with very large differences in concentrations and in which several compounds are present, the reproducibility and repeatability of the compounds of minor importance might be influenced.

The method has been validated for a selection of typical aromatic hydrocarbons[1].

This procedure is compatible with low flow rate personal sampling equipment, and can be used for personal and fixed location sampling for obtaining time-weighted-average concentrations of aromatic hydrocarbon solvent vapours in air. It cannot be used to measure instantaneous or short-term fluctuations in concentrations. Alternative on-site procedures, such as gas chromatography or infrared spectrometry, shall be used to measure rapidly changing concentrations.

Organic components which have the same or nearly the same retention time as the substance analysed during the gas chromatographic analysis will interfere. Interferences can be minimized by proper selection of gas chromatographic columns and programme conditions.