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RECEIVED for review April 10, 1980. Accepted June 11, 1980.
Determination of Polychlorinated Biphenyls in Silicone Fluids Helen M. Klimisch" and Donald N. Ingebrigtson
Downloaded by UNIV OF MANITOBA on September 2, 2015 | http://pubs.acs.org Publication Date: September 1, 1980 | doi: 10.1021/ac50061a032
Do w Corning Corporation, Midland, Michigan 48640
Two independent methods, using gas chromatography (GC) and high performance liquid chromatography (HPLC), have been developed for the determination of polychlorinated biphenyls (PCB) in polydimethylsiloxane(PDMS) fluids. For low levels ( C 5 ppm) of PCB, charcoal column chromatography is used to separate the PCB from the slloxane matrix for subsequent GC analysis. At higher levels, the sample may be diluted in hexane and analyzed directly by gas chromatography with electron capture detection. For HPLC with UV detection, the PCB are separated from the siloxane by an acetonitrile extraction and analyzed by reverse-phase chromatography. The GC method is preferred for low concentratlons of PCB. HPLC Is often convenient for higher PCB levels or when trichlorobenzene concentrations are to be determined. The lower detection limit for PCB by GC is 25 ppb (wt/wt). The lower detection limit for PCB by HPLC is 100 ppb. I f interfering species are present, the detection limits may be higher.
For a number of years, askarels have been used as dielectric coolants and heat exchange fluids. T h e term askarels refers t o fluids composed of polychlorinated biphenyls (PCB) containing 0 t o 50% trichlorobenzene (TCB). In the late 1960's, several unfortunate incidents occurred resulting from the toxic effects of P C B on man and animals. T h e environmental studies t h a t followed resulted in legislation to eliminate the use of P C B in t h e United States. Polydimethylsiloxane (PDMS), 50 centistoke, is an excellent candidate for replacement of askarels. Most importantly, the fluid is inert, has low toxicity ( I , 2) and offers no serious threat t o t h e environment (3-5). P D M S is currently being used as a dielectric coolant in the manufacture of new transformers as well as a replacement coolant in existing installations (6). Transformers retrofilled with silicone oils require subsequent charcoal treatment to remove residual PCB extracted from the insulation, laminates, paper, and other materials of construction during the initial weeks of operation. During the cleanup, both P C B and T C B are adsorbed by the charcoal. Analytical methods were needed t o identify and quantify the levels of P C B and TCB remaining in the silicone fluid during and after clean-up procedures. Methods for the determination of PCB in aqueous streams, organic oils, fish, and animal tissue have been reviewed by Hutzinger e t al. (7). However, these methods could not be 0003-2700/80/0352-1675$01 OO/O
applied directly to PCB in silicone oils because the procedures are incapable of separating the P C B from the silicone and other oleophilic contaminants. In the present study two independent methods have been developed for the analysis of trace quantities of P C B in PDMS. T h e techniques can be used interchangeably within certain limits. For routine analyses, a simple dilution of the sample for separation and detection by electron capture gas chromatography (EC-GC) is suggested. However, for quantitation of the T C B level, high Performance liquid chromatography (HPLC) is recommended. Fluids contaminated with ultraviolet (UV)-absorbingcomponents other than T C B and P C B may necessitate the use of a specific detector such as electron capture (EC). T h e H P L C method is more easily adapted to measure P C B levels >1% and still remain within t h e detector linearity. T h e EC-GC method is more straightforward with less interference from extraneous contaminants for P C B concentrations < LO ppm. Extremely low PCB concentrations,
