Particulate filter sampling

Sample Extractions. Both filter particulate samples and Tenax adsorbent samples were extracted with organic solvents to remove the adsorbed organic material. Pentane was used for Soxhlet extraction of Tenax samples whereas dichloromethane was used for ultrasonic extraction of particulate filter samples (5). Extracts were concentrated by rotary evaporation. For gravimetric analyses of some of the extracts, the concentrate from the rotary evaporator was transferred to a small vial and taken to dryness under a stream of nitrogen. 

Total airborne particulates are determined using a high-volume air sampler equipped with either cellulose fiber or glass fiber filters. Samples taken from urban environments require approximately 1 h of sampling time, but samples from rural environments require substantially longer times. 

Method 25 applies to the measurement of volatile organic compounds (VOC) as nonmethane organics (TGNMO), reported as carbon. Organic particulate matter will interfere with the analysis, and, therefore, in some cases, an in-stack particulate filter will be required. The method requires an emission sample to be withdrawn at a con-... 

Because a filter sample includes particles both larger and smaller than those retained in the human respiratory system (see Chapter 7, Section III), other types of samplers are used which allow measurement of the size ranges of particles retained in the respiratory system. Some of these are called dichotomous samplers because they allow separate measurement of the respirable and nonrespirable fractions of the total. Size-selective samplers rely on impactors, miniature cyclones, and other means. The United States has selected the size fraction below an aerodynamic diameter of 10 /xm (PMiq) for compliance with the air quality standard for airborne particulate matter. 

Figure 15-1 shows the Los Angeles, California, basin stationary air monitoring network, one of the most extensive in the United States (6). At most of these locations, automated instruments collect air quality data continuously. Five pollutant gases are monitored, and particulate matter filter samples are collected periodically. 

PCCD/PCDFs have been found to be present in Arctic air samples, e.g. during the winter of 2000/2001 in weekly filter samples (particulate phase) collected at Alert in Canada. PCDD/PCDFs have been monitored since 1969 in fish and fish-eating birds from the Baltic. The levels of PCDD/PCDFs in guillemot eggs, expressed as TEQ, decreased from 3.3 ng/g lipids to around 1 ng/g between 1969 and 1990. Since 1990, this reduction seems to have levelled off and today it is uncertain whether there is a decrease or not. Fish (herring) show a similar picture. 

The problem with filter sampling is that only particulate matter is collected. In many cases the concentration of organometallics is of interest. Robinson (83) has des-... 

Fresh ambient particulate POM sampled near a freeway was also exposed in this passive system for 3 h in the dark to 200 ppb of 03 in air at 1% RH. Concentrations of specific PAHs determined in the ambient particles and their percent reacted were similar for samples collected on both kinds of filters (glass fiber and TIGF). Again, under passive exposure conditions to approximately ambient levels of 03, BaP and BaA were found to be significantly more reactive than BeP. 

Modified filter sampling methods that are available will measure ambient levels of strong acid in ambient aerosol samples, and these methods do so with acceptable precision and accuracy [as indicated by the balance between measured anions and cations (56, 57)] in the absence of significant levels of particulate weak acids. Additional intercomparisons involving intrinsically different techniques for particulate strong acidity [e.g., IR spectroscopy (48), thermal speciation (38, 45), and filter methods (28)] are needed. Further information on the occurrence of various weak acids in airborne particles is needed, along with further studies of techniques for their specific determination in atmospheric aerosol samples. 

Speciation. Most of the Mn found in the water column of Lake RBR occurred in the Mn(II) oxidation state, as both soluble-colloidal and particulate species. This conclusion rests on the following evidence. At station 120, for all of 1988 at all depths (N = 52), there was no statistically significant difference between total Mn determined by AA spectrophotometry on unfiltered samples after acidification (0.62 mg/L), dissolved Mn determined by AA spectrophotometry on filtered samples after acidification (0.60 mg/L), and Mn2+ determined by ESR spectroscopy on unfiltered samples (0.63 mg/L). 

Microspectroscopy applies the identification power of infrared spectroscopy to the microscopic realm. Contaminants on printed circuit boards, blemishes in coatings, and other production defects can be isolated in situ and analyzed (see Electronics, coatings). Analysis of flaws that develop during use illuminates the method of failure. Microscopic samples, such as particulates filtered from air, can be analyzed individually. The forensic applications are many paint chips, single fibers, explosive residues, and inks on currency can all be identified nondestmctively (see Forensic chemistry). The structures of layered materials, such as laminated polymer films, are studied via microspectroscopy by cross-sectioning the materials and examining the individual layers edge on (47). 

That depends on what you are analyzing. Interfering compounds need to be removed as much as possible proteins precipitated, lipids extracted, cells and particulates filtered or removed. Some samples need to be concentrated to aid in detecting trace amounts in dilute samples. Check the literature for your particular compound, use traditional procedures for compound purifications, and look into the possibility of using SPE columns for pre-column purification and concentration (see Chapter 12). 

The May Pack has been used world-wide to characterise radioiodine. In some applications, glass fibre-filters have replaced membrane filters and copper or silver gauzes have been used to trap elemental iodine. The separation of iodine species in the May Pack is at best qualitative. Some inorganic iodine vapour may be adsorbed on the particulate filter. Conversely, iodine adsorbed on particles, and trapped on the particulate filter, may be desorbed during extended periods of sampling. 

NIOSH has recommended Methods 7013 (FAAS) and 7300 (ICP-AES) for detecting aluminum and other elements in filter samples of workplace air particulates. The applicable working ranges are 0.5-10 mg/m3 for a 100-L air sample by Method 7013 and 0.005-2.0 mg/m3 for a 500-L air sample by Method 7300 (NIOSH 1984b). 

Particulate and gaseous atmospheric components have been sampled using a multiple-filter system. A Teflon filter for particle collection preceded four LiOH/ glycerol treated Whatman-41 filters in a stacked filter arrangement. Up to fifty elements were detected on the particulate filter, while ten elements (B, N, S, Cl,... 

Semivolatile analytes in vapor-phase samples are often associated with particulate matter or aerosols that are collected on glass or quartz fiber filters in a flowing air stream.1 However some semivolatile analytes that have higher VPs, for example, 3,3 ,5,5 -tetra-chlorobiphenyl in Fig. 8.2, can slowly vaporize from a particle trapped on a filter in the flowing air stream, and will be lost unless captured by an in-stream sampling device. Small glass or metal tubes containing polyurethane foam are often used to capture vaporized semivolatile analytes. Other-solid phase adsorbents, which are described in the next section, are also used to trap semivolatile analytes vaporized from particulate filters. 

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