Dust filter sampling

Inert material of the sampling device (bags, tubes, valves), no losses by diffusion Preflushing Prediction equipment Volume of the sample Sampling time.pump speed Storage time(<24h) Inert tube material (PTFE. stainless steel, glass) Preflushing Predilution equipment Heated probe jf Dust filters required... 

To remove lint, dust, or other solid material from the sample, filter sample using a 10-ml syringe fitted with a syringe filter holder and a nylon filter. 

When small samples (less than 200mg) are to be crystallized it is particularly important to remove traces of insoluble material and to avoid contamination by dust, filter paper, etc. Thus it is essential to use carefully cleaned glassware and purified solvents, and to filter the hot solution. The paratus shown in Fig. 11.1 is convenient for small scale (5-200mg) crystallizations. Place the sample in the bulb and wash it with a few drops cf solvent. The procedure is as follows ... 

Figure 12 Plot comparing calculated saturation indices of various minerals of interest in SLF blank, and filtered (<0.45 p,m) SLF leachates of an indoor WTC dust sample (WTC-20) and outdoor WTC dust sample (WTC-16). The extreme supersaturations in the WTC dust leachate samples may result in part (but not entirely) from inclusion of some colloidal material less than 0.45 p,m in size in the analyzed filtrate.

Figure 1.4-1. Scheme of a sampling device for PCDDs/PCDFs, PAHs and PCBs 1 glass fiber filter, 2 solid sorbent (e.g. PUF or XAD-2), 3 pump, 4 timer, 5 dust filter, 6 cooling unit, 7 flow meter. 

Many proposals have been made in which OM (mainly PAni) blends could be used. Some of them are visionary and creative, like roofs coated with photovoltaic cells, wallpaper with electrical heating capability, heated textiles, dust filters, and many more [62]. Often the expectation that such blends would have properties superior to those of carbon black-fiUed blends, in conductivity or in mechanical or colour aspects, guided the vision. Whereas PAni blends can actually deliver somewhat higher conductivity values (up to 50 S/cm, the best value for laboratory samples, see Ref [22b] and Ref [23a], 5 S/cm for technical scale [65]) compared to those of carbon black compounds (best values around 0.5 S/cm), the other presumed advantages are not there. Nor are mechanical or processing properties, electrochemical stability under applied voltage and current (like for heating devices), or the color aspects of PAni blend any better than with carbon black compounds. 

Analysis of the resulting filter samples would be possible by nondestructive methods such as gamma spectrometry or X-ray fluorescence but these do not represent the most sensitive methods. Bulk analysis would be affected by the high dust loading of the filter and perhaps by the filter material itself, e.g., glass-fiber filters would be difficult to destroy chemically... 

Fig. 12-10. Schematic view of the analytical system for mercury determination by CVAFS (CVAAS) 1 pressure bottle for inert gas (Ar, N2,...) 2,15 flow meters 3 dust filter 4 gas-cleaning trap (Au) 5 reaction vessel (500 mL) (including stirring bar, PTFE-encased), seawater sample (200 mL) and (magnetic) stirring device) 6 three-way cocks 7 septum (Hg injection) 8 collection trap (Au) 9 analytical trap (Au) 10 voltage control 11,12 gas outlets (optional via three-way cocks) 13 AFS (AAS) detector and 14 mercury scrubber (charcoal trap).

Preparation of REAOENTS.t It is essential for this preparation that the zinc powder should be in an active condition. For this purpose, it is usually sufficient if a sample of ordinary technical zinc powder is vigorously shaken in a flask with pure ether, and then filtered off at the pump, washed once with ether, quickly drained and without delay transferred to a vacuum desiccator. If, however, an impure sample of zinc dust fails to respond to this treatment, it should be vigorously stirred in a beaker with 5% aqueous sodium hydroxide solution until an effervescence of hydrogen occurs, and then filtered at the pump, washed thoroughly with distilled water, and then rapidly with ethanol and ether, and dried as before in a vacuum desiccator. The ethyl bromoacetate (b.p. 159 ) and the benzaldehyde (b.p. 179 ) should be dried and distilled before use. 

Various methods are used for evaluatiag the quaflty, ie, physical strength and ensyme dust formation, of the granulate. In the elutriation process, a sample of product is fluidised ia a glass tube with a perforated bottom plate for 40 miautes. Dust from the sample is collected oa a filter and the ensyme activity measured. An acceptable dust level is when less than 5—10 ppm of the activity of the sample has been collected. In the so-called Heubach method, 20 g of granulate is elutriated. During the elutriation, four steel balls are rotated ia the bed ia order to evaluate the impact of attritioa oa the dust release of the ensyme. The dust is collected oa a filter and measured. The acceptable dust level is very low. 

Simple gravimetry of the sample is likely to be an integral component of the determination of, e.g., the concentration of, or exposures to, airborne dust. Care is required to avoid errors arising from absorption of atmospheric moisture. Tliis can be avoided by using blank filters, by conditioning the filters in an atmospherically-controlled room, or use of a desiccator. 

Discrimination between fire types in samples of airborne dust on filters using microscopy... 

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