EPA Method 9079
Method 9079 may be used to screen hydrocarbon based electrical insulating fluids for polychlorinated biphenyls (PCBs) at preset levels of 20, 50, 100, or 500 µg/g. The method is designed to provide screening data outside of a laboratory environment in under 10 minutes, providing a colorimetric indication that the concentration of PCBs is above or below the fixed end point. Screening procedures may significantly reduce the number of samples requiring laboratory testing. 1.2 Chlorines are removed from the PCB molecule using an organo-sodium reagent. The resulting chloride ions are measured using a colorimetric indicator. 1.3
This method is restricted to use by or under the supervision of trained analysts. Each analyst must demonstrate the ability to generate acceptable results with this method. 2.0 SUMMARY OF METHOD 2.1 A sample of the oil to be tested is reacted with a mixture of metallic sodium catalyzed with naphthalene and diglyme at ambient temperature. This process converts all organic halogens to their respective sodium halides. All halides in the treated mixture, including those present prior to the reaction, are then extracted into an aqueous buffer, a premeasured amount of mercuric nitrate is added, followed by a solution of diphenylcarbazone as the indicator. 2.2
The color of the solution at the end of the test indicates whether the sample is above or below the preset chlorine level. A yellow end point indicates a concentration greater than the set point of the test and a blue-violet end point indicates a concentration less than the set point of the test. 2.3 The end point at which each of the test kits turns positive is calibrated using Aroclor 1242 standards. Aroclor 1242 provides a conservative end point due to its low chlorine content relative to the other Aroclors used in electrical equipment. A list of Aroclors used in electrical equipment and the PCB concentration that gives a positive indication using the 50 µg/g test kit is given in Table 1.
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