Location of Pentachlorophenol By Electron Microprobe and Other Techniques in Cellon Treated Douglas-Fir

Specimens of Douglas-fir were analyzed to determine the exact location and concentration of pentachlorophenol (PCP) after pressure impregnation by the Cellon process. Results from staining with chlordioxide and dimethylanilin indicated that PCP was located not only on the cell surfaces but also within the cell walls themselves. Specimens were also selectively extracted up to 12 days with benzene (which does not swell the wood structure) with the thought of removing surface PCP while leaving any PCP in the cell walls. These samples were then analyzed for PCP using X-ray spectroscopy. The results also indicated the presence of PCP in wood cell walls, although the data for sapwood were not as consistent as those for heartwood. Final examination of specimens was made using an electron probe microanalyzer testing for chlorine within cell walls. Data were collected on earlywood, latewood, and ray cells at various depths within treated boards. All three tissue types were found to have PCP within their cell walls. Latewood cells had more PCP than earlywood cells with ray cells having the greatest amount of the three. Sample boards treated at pressures of 30 and 60 psig were found to have less PCP totally and in, the cell walls than those impregnated at 100 and 145 psig. No significant difference was detected, however, between boards treated at 100 and 145 psig. Several possible explanations were advanced for the entrance of PCP into the cell walls.

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