*2.4. Copper Characterization*

To assess the impact of the peroxide treatment on the form of copper present in the treated wood, six red pine sapwood specimens (25 mm × 50 mm × 15 mm) were pressure impregnated with MBCC. Three of these specimens were then dip treated in a 20% aqueous solution of hydrogen peroxide. All specimens were then milled to pass through a 40-mesh screen. The resulting sawdust was analyzed by x-ray fluorescence spectroscopy for total copper. The remaining sawdust from each specimen was analyzed by Electron Paramagnetic Resonance (EPR) spectroscopy at the University of British Columbia (Vancouver, BC, Canada) using the methods developed by Xue et al. [21]. A Bruker Elexsis E500 series continuous wave EPR (Bruker BioSpin GmbH, Rheinstetten, Germany) was used for the analysis. The operating parameters were 77 K, at a frequency 940 GHz (X-band), 100 KHz field modulation and 1 G modulation amplitude. Frequency calibration was independently verified using 2,2-diphenyl-1-picrylhydrazyl. The spectral simulation was achieved using SIMFONIA (Bruker Biospin GmbH, Rheinstetten, Germany). Integration was OriginPro8 (Origin Lab). Baseline correction was applied before calculating the area under the curve. The sample tube was packed with wood sawdust to a height greater than 100 mm so that it exceeded the cavity height, thereby minimizing variation caused by the sample content.
