Validation of a measurement method for cyproconazole retention in pressure-treated wood through an interlaboratory study

The Japanese Agricultural standard (JAS) defines national regulations for preserved wood and wooden materials, in Japan. Traditionally the JAS focused on quality of product, however, the revision of the JAS Act in 2017 enabled standardisation of test or measurement method for the quality evaluation. The Japan Wood Protection Association (JWPA) has been working toward standardisation of methods for determining wood preservatives retention in treated wood. This presentation reports on an inter-laboratory study to evaluate a method for measuring the retention of cyproconazole (CYP) in pressure-treated wood using CUAZ and AZN, in accordance with ASTM E691. In this method, CYP is extracted from treated materials using ultrasound extraction with methanol and quantified by high-performance liquid chromatography (HPLC) with UV detection. Solid phase extraction was employed to remove wood components that could interfere with HPLC-UV analysis. Nine laboratories participated the interlaboratory study. Test samples at six concentration levels of CYP were prepared, and each laboratory carried out measurement for three samples in each concentration level. The results from the laboratories were analysed to determine within-laboratory relatively standard deviation (repeatability) and between-laboratory relatively standard deviation (reproducibility). These results confirmed the validity of the measurement method for CYP in treated wood materials.