Quartz fibre filters

Sampling of these substances has been carried out following three approaches liquid absorbents [47], solid-phase microextraction (SPME) fibres [43] and filter substrates (mostly quartz fibre filters but also PTFE membranes [1, 42, 48, 49]). When filter substrates are used, atmospheric particles are collected over 24-h periods using high-volume (dichotomous or single-filter instruments [1, 48]), medium-volume or low-volume samplers (operated to ensure collection of sufficient aerosol mass [37, 50]). Samples were always stored at low temperamres (refrigerated or frozen) to ensure sample preservation. 

A high-volume sampler equipped with a size selective inlet and a quartz fibre filter was used to collect particulate matter less than or equal to 10 pm in diameter, PMi0 (Figure 1) [ ] ... 

At the Eotvos Lorand University - Department of Chemical Technology and Environmental Chemistry, a coupled Eulerian photochemical reaction-transport model and a detailed ozone dry-deposition model for the investigation of ozone fluxes over Hungary have been developed and are used in collaboration with Leeds University of the UK. As part of a research project with Ghent University, aerosol samples were collected using several filter-based devices (Nuclepore polycarbonate membrane. Teflon membrane and quartz fibre filters) over... 

Pressurized liquid extraction (PLE) or accelerated solvent extraction (ASE) can be used e.g. to desorb PEGS bound to airborne particles collected on a quartz fibre filter (Sasaki et al. 2003). Nine pesticides were extracted from PM2.5 by a rapid PLE procedure using acetone (Coscolla et al. 2008). Regarding indoor dust, different solvents have been chosen for PLE extraction of several compounds such as parabens and triclosan (Canosa et al. 2007), PCBs (Harrad et al. 2009), PAHs (Naspinski et al. 2008), PBDEs (Toms et al. 2009 Sjodin et al. 2008 Stapleton et al. 2008), and hexabromocyclododecanes (HBCDs) (Harrad et al. 2009). 

For the determination of particulate mercury, add-cleaned Teflon and quartz fibre filters, the latter combusted at 500 °C (Coquery and Cossa, 1995), are recommended. A significant fraction of the mercury in seawater is present in colloidal forms and separated with the aid of add-cleaned ultrafiltration cartridges (Stordal et oL, 19%). 

Gas chromatography, coupled with flame-ionisation, electron capture (for halogenated species) and mass spectrometric detectors, is the most popular tool for determination of SVOCs in melted snow samples [44]. A prerequisite is the efficient separation of the analytes from the aqueous matrix, which can be accomplished using filtration onto quartz fibre filters and sohd phase extraction [88]. Solid phase micro-extraction, which utilises equihbrium-based adsorption of analytes onto a polymer fibre bundle, has also been proposed and tested in laboratory studies [13, 89]. Both methods allow for an efficient transfer into the injection port of a gas chromatograph without water contamination. Directly coupled inlet sampler with GC-EID instrumentation has also been used [90]. The air sample was pre-concentrated using adsorbents (Carbotrap B, Carbosieve), followed by heating and collection on a cryofocuser (a fused silica capillary tube packed with... 

Chromium speciation is very often performed in workplace air and a careful selection of the filter medium used for collecting dusts is of paramount importance. Cellulosic filters and glass fibre filters containing binders are ordinarily unsuitable, as these filter types can lead to significant reduction of Cr(Vt). Filter materials acceptable for sampling of airborne Cr(VI) include PVC, PVF, PTFE or quartz fibre filters. ... 

Filtration Is the sampling method most frequently used in industrial hygiene work (personal monitors) on account of its operational simplicity. A filter assembly typically consists of a sampling head and a filter (passive atmospheric samplers) or a sampling head, filter and pump (active samplers), all of which are constructed In a material introducing no contamination In the samples. The different types of filters (depth, membrane) and materials (glass fibre, quartz, cellulose esters, PFTE, sliver) used can be readily adapted to the unknown analyte. 

The abrasive forces in this context arise from the shape and the nature of the particles in the slurry. Materials with hard, sharp quartz-like edges may lead to internal abrasion, the breakage of fibres and filaments and ultimately a weak point, and possibly a pinhole in the fabric. Being the point of the lowest resistance to flow, enlargement of such a hole then follows (Fig. 3.15), eventually resulting in excessive solids in the filtrate. The filter fabric should therefore be designed, as far as possible, to withstand the impact of such forces. This may be achieved by appropriate yam and fabric constmc-tion, ideally manufactured from the toughest polymer consistent with the chemical conditions in the application. 

Figure 1 A diagram of the optical arrangement of a stopped-flow system capable of simultaneous observation of changes in absorbance and fluorescence. The light from the xenon lamp is diffracted by monochromator 1 (MCMl) to select the excitation wavelength. Usually quartz optical fibres conduct the light to the observation cell and absorption is detected at 180° and fluorescence emission (wavelength selected by a cutoff filter or MCM2) Is detected at 90° relative to the incident light...

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