A preliminary study of preservative retention and penetration in ACQ-treated timbers using near infrared spectroscopy
Near infrared (NIR) spectroscopy has been previously used in our laboratory to predict copper, chromium, and arsenic levels in samples of chromated copper arsenate (CCA)-treated wood. In the present study, we utilized our custom-made NIR scanning system, NIRVANA (near infrared visual and automated numerical analysis), to scan cross sections of ACQ (alkaline copper quat)- treated timbers to assess whether this technology can be used as a quality control tool for wood treaters. Models for CuO retention were created using ACQ-treated and untreated southern yellow pine (SYP) wood blocks. Strong correlations were obtained between the CuO retentions predicted by NIR and those based on elemental analysis. NIRVANA was then utilized for automated spectra collection from ACQ-treated SYP timbers. The resultant plots showed both the variation of CuO retention and the preservative penetration depth along the specimens from the pith to the timber surface. NIRVANA appears to be ideally suited to the assessment of ACQ- treated timber providing both rapid and detailed analysis of the preservative treatment applied to the timber. This preliminary study will be extended to other preservative components (e.g., organic co-biocides), in which the preservative penetration and concentration cannot be readily assessed.