EPR is currently being used to help elucidate the nature and extent of the chemical reactions occurring between wood and copper based timber preservatives. In the work reported here treated Scots pine samples were examined at room temperature and in the frozen state. Plots of the electronic parameters A|| vs. g|| were found to be a useful index of the electronic properties of the various formulations. Those containing copper bound to nitrogen could clearly be distinguished from chromated-copper and other nitrogen-free systems and the technique was extremely useful in the interpretation of spectra where a formulation generated more than one copper signal. In two of the nitrogen containing systems one of the forms of copper, identified as being bound to nitrogen was well fixed whereas the other form, not bound to nitrogen, was more leachable. In the chromated-copper formulations tested (CC and CCA) a small amount of the chromium was identified as a stable concentration dependent Cr(V) species (g = 1.974 - 1.978) which presumably disproportionates during leaching into Cr(III) and Cr(VI). In general, chromated copper formulations gave poor quality spectra in comparison to copper only formulations and this should allow the newer, chromium free preservatives to be more widely studied by EPR.

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