Sampling is performed using a high volume sampler. Particle bound polycyclic aromatic hydrocarbons (PAHs) are collected on a glass fibre filter, and more volatile PAHs are adsorbed to plugs of polyurethane foam (PUF) placed behind the filter. The filter and the plugs are soxhlet extracted with cyclohexane after sampling. The pre-concentrated extracts are cleaned using liquid/liquid extraction and HPLC before analysis using high-resolution gas chromatography combined with mass spectrometry (GC/MS).
Sampler:
NILUs PUF-High-volume sampler (see 3.13.2)
Pump: Siemens ELMO-vacuum pump
2BH5
Glass
fibre filter: Type A/E, 142 mm, Gelman no. 61635 (cleaned)
PUF-plugs:
11 x 5 cm (diam. x h), density 25 kg/m3, white type (cleaned)
PUF
may be replaced with XAD-2.
Aluminium
foil
Plastic
gloves
Tweezers
XAD-2,
polystyrene divinylbenzene co-polymer, 0.3-0.85 mm particle size
Similar or better qualities from other manufacturers may be used. For sampling also Sierra, Anderson or similar high volume samplers may be used.
All glass equipment must be decontaminated before use. Leave the equipment in 2.5% RBS in water for 16 hours. Flush well with hot tap water followed by MilliQ water. Leave to dry on a clean surface.
Put ca 50 filters (Gelman-Type A/E, 142 mm) on an Al-foil and heat to 450°C for 8 hours. After cooling to room temperature wrap each filter in Al-foil.
Extract thimbles for 8 hours ("1 day") with cyclohexane in a 600 ml soxhlet extractor. Dry in a desiccator connected to a vacuum pump (capacity 2.4 m3/h, and 80 kPa (0.8 bar) at 100°C. Connect pump outlet to a cooler to condense solvent. Wrap dry thimbles in Al-foil.
Dismantle the sampler. Wash glass, metal parts and gaskets with warm detergent (2.5% RBS 25 in water). Flush all parts except the gaskets, with warm water, distilled water and acetone. Flush the gaskets with warm water, distilled water, not acetone.
Clean new PUF-plugs with toluene (Merck no. 8389) in a 2000 ml soxhlet extractor. The extractor can take up to 8 plugs simultaneously. Use a 3000 ml round bottomed flask and fill toluene into the extractor until it empties the content into the round bottomed flask. Add ca. 500 ml toluene and mount the lid and cooler. Turn on the heater and the cooling water. Extract the plugs for 24 hours.
Squeeze toluene out of the plugs (solvent resistant gloves!) and transfer the plugs to another 2000 ml soxhlet extractor. Acetone is added as prescribed for toluene and the plugs are extracted for 8 hours.
Finally, extract with cyclohexane (new extractor) for 8 hours.
Observe! Used plugs (which previously have passed trough the whole cleaning procedure, toluene included) can be cleaned as follows:
1)
Soxhlet extraction with acetone for 8 h
2)
Soxhlet extraction with cyclohexane for 8 h
After final extraction squeeze the cyclohexane out of the plugs. Place the plugs in a desiccator. Put the desiccator in an oven at 60°C, and connect desiccator to a vacuum pump. Dry for 16 hrs and wrap the plugs in Al-foil individually. Store pairs of plugs and a filter in zip-shut plastic bags.
Fill XAD-2 in a thimble and put it in a soxhlet extractor. Extract for 8 h with each of the following solvents: Methanol, acetonitrile and diethyl ether. Leave the wet adsorbent on an Al-foil in a fume hood until it appears dry. Dry in an oven at 35°C overnight.
NILU's high volume sampler consists of a glass cylinder (10 cm diam.) with a filter holder at one end. The other end is connected to a Siemens vacuum pump with a hose. Before starting sampling it is important that the plugs fit firmly to the glass wall without forming channels
See chapter 3.13.3 for the sampling procedure using the NILU PUF sampler.
All new samples are stored in a freezer until extraction.
For the most volatile PAHs, especially the bicyclic compounds, "break-trough" will occur at high air temperature and/or long sampling time. At sampling times longer than 6 h and temperature 20 °C (or higher) a break-trough will normally occur for the bicyclic PAHs, and these should not be reported with accreditation.
For sampling XAD-2 may be used instead of PUF.
If the amount of particles in the sample is to be determined, the filter must be weighed before and after sampling. Condition the filter for 24 h at constant temperature and humidity before weighing.
Fold the filter over twice and cut the rim with a scissors cleaned with cyclohexane. Transfer the filter to a thimble (28 x 80 mm), in a 60 ml soxhlet extractor. Add internal standard directly to the filter using a 10, 20, 50 ml or 100 ml syringe or micropipette. Use 100 ml cyclohexane in a 250 ml round bottomed flask for the filter extraction.
Transfer the two PUF plugs to a 500 ml extractor, add internal standard, extract with 500 ml cyclohexane and use a 1000 ml round bottomed flask. Extract filter and plugs for 8 h (1 day).
If only the total PAH content in the sample is wanted, the whole amount of internal standard is added to the filter. Use 500 ml cyclohexane and a 1000 ml round bottomed flask for the extraction. After the filter extraction, remove the 60 ml extractor and replace with a 500 ml extractor containing the plugs. Continue the extraction without further addition of internal standard.
After the extraction, transfer the solvent in the extractor to the flask.
If the filter and plugs are to be analysed separately, the extracts must be cleaned separately. The extract is pre-concentrated before clean-up.
Extraction of XAD-2 is done using cyclohexane in a soxhlet extractor for 8 h. XAD-2 is transferred to a thimble of suitable size and internal standard is added before the extraction is started.
Pre-concentration is normally performed using a TurboVap pre-concentration system. This system has an automatic stop at a final sample volume of 0.5 ml. Manual control must be made to stop the pre-concentration at 4 ml.