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Method TO-10A Pesticides/PCBs <br /> 6.2 The ECD responds to a wide variety of organic compounds. It is likely that such compounds will be <br /> encountered as interferences during GC/ECD analysis. The NPD,FPD,and HECD detectors are element specific, <br /> but are still subject to interferences. UV detectors for HPLC are nearly universal, and the electrochemical <br /> detector may also respond to a variety of chemicals. Mass spectrometric analyses will generally provide positive <br /> identification of specific compounds. <br /> 6.3 PCBs and certain organochlorine pesticides(e.g.,chlordane)are complex mixtures of individual compounds <br /> which can cause difficulty in accurately quantifying a particular formulation in a multiple component mixture. <br /> PCBs may interfere with the determination of pesticides. <br /> 6.4 Contamination of glassware and sampling apparatus with traces of pesticides or PCBs can be a major source <br /> of error,particularly at lower analyte concentrations. Careful attention to cleaning and handling procedures is <br /> required during all steps of sampling and analysis to minimize this source of error. <br /> 6.5 The general approaches listed below should be followed to minimize interferences. <br /> 6.5.1 Polar compounds,including certain pesticides(e.g., organophosphorus and carbamate classes)can be <br /> removed by column chromatography on alumina. Alumina clean-up will permit analysis of most organochlorine <br /> pesticides and PCBs(4). <br /> 6.5.2 PCBs may be separated from other organochlorine pesticides by column chromatography on silicic acid <br /> (5,6). <br /> 6.5.3 Many pesticides can be fractionated into groups by column chromatography on Florisil(6). <br /> 7. Equipment and Materials <br /> 7.1 Materials for Sample Collection <br /> 7.1.1 Continuous-Flow Sampling Pump (see Figure 1). The pump should provide a constant air flow <br /> (:!�±5%),be quiet and unobtrusive,with a flow rate of 1 to 5 L/min. Sources of equipment are Supelco, Supelco <br /> Park,Bellefonte,PA; SKC, 334 Valley View Road,Eighty Four,PA and other manufacturers. <br /> 7.1.2 Sampling Cartridge(see Figure 2). Constructed from a 20-mm(I.D.)x 10-cm borosilicate glass tube <br /> drawn down to a 7-mm (O.D.) open connection for attachment to the pump by way of flexible tubing (see <br /> Figure 1). <br /> 7.1.3 Sorbent,Polyurethane Foam(PUF). Cut into a cylinder,22-mm I.D. and 7.6-cm long,fitted under <br /> slight compression inside the cartridge. The PUF should be of the polyether type, (density of 0.0225 g/cm3). <br /> This is the type of foam used for furniture upholstery,pillows,and mattresses. The PUF cylinders(plugs) should <br /> be slightly larger in diameter than the internal diameter of the cartridge. The PUF sorbent may be cut by one of <br /> the following means: <br /> • With a high-speed cutting tool,such as a motorized cork borer. Distilled water should be used to lubricate <br /> the cutting tool. <br /> • With a hot wire cutter. Care should be exercised to prevent thermal degradation of the foam. <br /> • With scissors,while plugs are compressed between the 22-mm circular templates. <br /> Alternatively,pre-extracted PUF plugs and glass cartridges may be obtained commercially. <br /> Page 10A-4 Compendium of MethodsJor Toxic Organic Air Pollutants January 1999 <br />