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Show improve recovery [20, 21] although performance of this procedure and acceptability by regulatory agencies has not been well-established. When combining sample trains, the fmal recovery rinse to be included in analysis is usually toluene. This should be followed by a final hexane rinse to remove traces of toluene which may contaminate subsequent P AH sample analysis if the equipment is reused. One of the key problems with this procedure has been high background levels of naphthalene. This is a contaminant of the XAD-2 sorbent resin manufacturing process. Improved procedures for pre-test cleaning of the XAD-2 resin have been developed to minimize naphthalene contamination [17]. EER's experience shows that this leads to improved (lower) naphthalene contamination but that detectable background levels are still found in many cases. Thus, quantification of naphthalene emissions remains uncertain if concentrations in the flue gas are very low. Contamination also is an issue and appropriate precautions in the field should be taken such as installation of activated carbon air futers and prohibition of smoking in sample handling areas, requiring personnel to scrub before handling samples, recovering high-level and low-level samples in different areas, etc. Formaldehyde and Other Carbonyls Emissions of carbonyls such as formaldehyde and possibly other aldehydes and ketones are detennined by derivitization of carbonyls in aqueous acidic 2,4 dinitrophenylhydrazine (DNPH). The sample is drawn through impingers containing the DNPH solution as illustrated in Figures 2e and 2f. Aldehydes react with the DNPH by nucleophobic addition on the carbonyl followed by 1,2-elimination of water and formation of a hydrazone derivative. The formation of the derivative stabilizes the aldehyde in the solution. After organic extraction and concentration, the solution is analyzed using reverse-phase high performance liquid chromatography (HPLC) with an ultraviolet absorption detector operated at 360 run. Two test methods using this technique are EPA Method 0011 [22] and CARB Method 430 [16]. One of the key problem areas with this technique is high formaldehyde background levels. This is generally believed to be due to contamination of the sample in the field or in the laboratory when handling the sample. Ambient air, personnel respiration, carpeting and construction materials in the sample handling areas are potential sources of formaldehyde contamination. Another problem is acetone contamination, which is extremely difficult to avoid because it is a ubiquitous solvent in the field and in the laboratory. CARB Method 430 has the advantage of using 50 ml (midget or Wheaten) impingers. If screw-top impingers are used in the field, once sampling is completed they 7 |