Quantification of mobilized copper(II) levels in micronized copper-treated wood by electron paramagnetic resonance (EPR) spectroscopy

Abstract

Sapwood sawdust from southern pine was treated with micronized copper (MC) under various conditions and the mobilized copper(II) (Cu mob ) concentrations were determined in the treated wood by electron paramagnetic resonance (EPR) spectroscopy. The spectral parameters for the copper sulfate (CuSO 4 )-treated sapwood and those of the MC-treated sapwood were very similar. A linear correlation was found between the intensities of copper (Cu) EPR spectra and those of Cu energydispersive X-ray fluorescence spectroscopy in a series of CuSO 4 -treated sapwood reference samples. Thus, the EPR signal intensities could be reliably correlated to the mass of reacted Cu present using this calibration curve. The amount of the Cu mob in sawdust treated by MC suspensions increased during the first 2-3 days after the initial treatment and then reached a maximum during the 7-day monitoring period. In the case of the treatment with MC alone or MC azole, an increased MC concentration led to an elevated amount of Cu (to a maximum of ∼0.23% Cu) solubilized by the sapwood. If the wood was treated with MC quat, the Cu mob initially increased, but at higher concentrations the Cu mob content decreased, due to the interference by the quat cobiocide on the acid reaction between the wood and the basic Cu carbonate. An examination of commercially-treated wood confirmed the laboratory observations.

Peroxide Post-Treatment of Wood Impregnated with Micronized Basic Copper Carbonate

“…These data demonstrate an association between the peroxide post-treatment and increased levels of reacted copper. The reacted copper content in the wood treated with micronized copper carbonate is typical of values previously reported [21,25]. The peroxide treatment may generate more reactive sites in the wood, leading to enhanced reaction between the wood and the micronized basic copper carbonate.…”

“…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.…”

Reacted copper(II) concentrations in earlywood and latewood of micronized copper-treated Canadian softwood species

“…Detailed methodology was reported by Xue et al (2012Xue et al ( , 2013. A series of sawdust samples treated with CuSO 4 solutions at 16 different concentrations was analyzed by EPR.…”

“…Earlier studies (Xue et al 2010(Xue et al , 2012 confirmed that hydrated Cu species were produced and fixed rapidly with wood upon treatment with an aqueous suspension of BCC. A quantification method based on EPR in combination with X-ray fluorescence (XRF) spectroscopy was developed for determining the reacted Cu concentrations in the treated wood (Xue et al 2013). In the study reported here, this quantification method will also be applied aiming at the investigation of the reacted and total Cu levels in EW and the LW of two Canadian softwoods, which were pressure treated with micronized Cu.…”

Micronized Copper Wood Preservatives: Efficacy of Ion, Nano, and Bulk Copper against the Brown Rot Fungus Rhodonia placenta

“…When wood is treated with MC, some Cu reacts with wood and part of it remains in the form of unreacted Cu particles that provide a reservoir effect [ 15 ]. Most of the studies [ 16 ] on Cu bioavailability of micronized Cu have focused on the release of Cu 2+ ions [ 17 – 21 ]. However, the superior efficacy of the treatment [ 22 – 25 ] may be partially due to insolubilized persistent CuCO 3 ·Cu(OH) 2 NPs that diffuse through the fungal cell wall and its membrane and exert their toxic effects, also described as the Trojan horse mechanism [ 26 ].…”