La noción de competencia interactiva de Habermas como herramienta

Each Hi-Vol w as equipped w ith a sam pling m odule. This m odule held a circular 10 cm diam eter W hatman G F /A filter (pore size 1.5 pm) and two in line p o ly u reth an e (PUF) foam plugs (vapour trap). The m odule could be rem oved as a single unit to prevent handling contam ination. The filters w e re b ak ed at 450 ®C for 14 h p rio r to m odule co n stru ctio n and gravim etrically weighed after cooling. The PUF plugs were pre-extracted in

dichlorom ethane (DCM) for 16 h, loosely w rapped in alum inium foil, and air dried in a clean air cabinet. The dried PUF plugs were placed into a pre­ cleaned glass sleeve which fitted into the m odule behind the filter head. An a lu m in iu m plate was screw ed into place over the exposed filter, and alum inium foil was w rapped over the rear air vent to avoid contam ination w hen the m odules were being transported.

The 5 L jar of the deposition sam pler was rinsed w ith DCM and MilliQ® w ater prior to its transport to the field. 25 mL of 5% copper sulphate solution w as ad d ed to the jar as an algicide. Similarly, the inverted metal frisbee and anti-splash m esh were thoroughly rinsed in DCM. A plastic cover was taped over the frisbee when in transport to and from the field or w hen in storage.

3.3.2 First stage sam ple clean up

A ir samples. A schematic diagram showing the steps taken for atm ospheric sam ple clean u p is presented in Figure 3.3. Basically this involved solvent extraction followed by solid phase extraction using open column adsorption chrom atography to remove interfering contaminants from the analyte.

The sam pling m odule was dism antled in the clean air cabinet and the PUFs w ere w rap p ed separately in alum inium foil. The filter was placed into a desiccator for 24 h and then re-weighed to obtain the mass of the collected particulate or total suspended particulate (TSP). TSP concentrations (pg n r 3)

Figue 3.3. Flow chart showing the various stages in sample clean up and analysis of air samples.

Filter sample

Solvent exchange to 10 mL of dichlorom ethane (PCM)

Elute through 1 g of Florisil™ and reduce volume to 1 mL Filter and PUFs separately extracted

in n-hexane for 16 hr

PAH analysis

HPLC - Fluorescence detector

Elute through 1 g Florisil™

Solvent exchange to 1 mL of dodecane Facilitate solvent exchange

to 10 mL of n-hexane 1st stage clean up 2nd stage clean up PCB analysis HRGC-ECD

are presented for the Manchester, Cardiff and Hazelrigg sites in A ppendix 1. The filter w as w rapped in alum inium foil and placed into a plastic bag, along w ith the PUF plugs and stored at 4 °C prior to analysis. Samples were stored for no longer than 1 m onth before analysis. Kloster et al. (1992) found sam ple integrity to be preserved for PAHs after 4 m onths of storage at room tem p eratu re. The PUF plugs and the glassfibre filters w ere extracted se p a ra te ly in a 6-place Biichi soxhlet u sing p esticid e-g rad e hexane (R athburns Ltd.). The extraction was run for 16 h, before being taken dow n to n e ar d ry n ess and rem oved from the soxhlet. Extracts w ere then quantitatively transferred to 10 mL glass vials, using several DCM washings (to facilitate solvent exchange). The volume was then gently reduced to 1 mL on a heating block (at 35 °C) under nitrogen. The 1 mL extract w as then passed through 1 g of Florisil™ (60-100 mesh) packed into a glass pasteur pipette and eluted with 9 mL of DCM. This volume was then reduced again to 1 mL, passed through a 0.5 pm syringe filter and transferred to H ew lett Packard (HP) 2 mL chromatography vials for analysis of PAHs.

Deposition samples. A schematic diagram showing deposition sam ple d e a n u p is presented in Figure 3.4. T he first step involved filtering th e w ater th ro u g h a 18.5 cm W hatm an p ap er filter to rem ove large p articu late m aterial. This filter w as carefully air d rie d in a d e a n a ir c ab in e t a n d so x h let

extracted along w ith a q u a rte r PU F p lu g u s e d to w ip e th e in te rio r o f th e

m etal frisbee. PAHs and PCBs w e re e x tracted w ih p e stic id e -g ra d e n-hexane

Figure 3.4 Flow chart showing the various stages in clean up and analysis of deposition samples.

Sample reduced to 1 mL and filtered

Disk w ashed with two 10 mL aliquots of DCM___________

Solvent exchange to 10 mL of DCM

Deposition filtered through 18.5 cm W hatman filter paper

Filtered w ater passed through conditioned C-18 extraction disk

Filter dried and extracted

with quarter PUF (frisbee wipe) for 16 h in n-hexane

DCM aliquots bulked and reduced to ~ 1 mL. Elute through 1 g Florisil

with a further 9 mLs DCM

PAH analysis

Elute through 1 g Florisil

Solvent exchange to 1 mL of dodecane Facilitate solvent exchange

to lOmL n-hexane

exchange to DCM after soxhlet extraction. The filtered water was conditioned w ith 5 mL of m eth an o l/L of water. This was then filtered through a pre­ treated C-18 Empore disk which retained organic compounds from the w ater sample. The C-18 disk was subsequently washed with two 10 mL aliquots of DCM; these were added to the DCM from the filter paper and PUF extract an d ev ap o rated u n d er a gentle stream of nitrogen. Clean u p by colum n chrom atography followed the same procedure as the air samples. In the case of dep o sitio n sam ples each Florisil™ colum n h ad ~0.2 g of anhy d ro u s sodium sulphate added to the column to remove any w ater left w ithin the sam ple.

3.3.3 Second stage sam ple clean up

A ir and deposition samples. After PAH analysis the 1 mL of DCM extract w as then gently evaporated under nitrogen and solvent exchanged back into 1 mL of hexane. This was eluted through 1 g of Florisil™ w ith a further 9 mL of hexane. This volume was gently evaporated under a nitrogen stream to approxim ately 5 mL. 1 mL of dodecane (Aldrich Inc.) was added and the volum e further reduced until 1 mL of dodecane was left (evaporative losses of dodecane were considered to be negligible relative to hexane). The final extract volume of dodecane, was transferred to a 2 mL HP vial for analysis of PCBs.