Aged wooden stake, extraction of wood, gas chromatograph and gas chromatogram of the extract

Aged wooden stake (A), extraction of wood (B), gas chromatograph (C) and gas chromatogram of the extract (D)

Source: BAM, Division Contaminant Transport and Environmental Technologies

The contents of biocidal active substances in treated wood need to be quantified to control the quality of treatments performed in the past, e.g. in wood that has already been in service. This is a task for laboratories from producers, material testing and research institutes. Applied analytical procedures differ among laboratories and include extraction of the substances in question from the wood followed by gas or liquid chromatography combined with different detectors.

For this study wood stakes with a known content of the biocides propiconazole, tebuconazole and permethrin were weathered outdoor by exposure to UV light and humidity over several years. Ten laboratories received samples from the weathered stakes along with samples from stakes kept dry in the dark for the same period of time and performed quantification of the biocides using their specific equipment combination of chromatography and detection.

The results revealed interfering signals in case of several liquid chromatographic methods, which affected quantification of tebuconazole and propiconazole by non-specific UV detection. This effect could be circumvented by optimization of the separation conditions or the use of mass selective detectors. Overall, slightly lower amounts of active substances were determined in weathered wood samples compared to samples stored dry in the dark. However, this difference was too small to be observed by liquid chromatography combined with UV detection due to the higher standard deviation among the respective laboratories.

Suitability of analytical methods to determine tebuconazole, propiconazole and permethrin in aged wood samples
Ute Schoknecht, Petra Drescher, Martin Fischer, Christina Fürhapper, Jan Gunschera, Rainer Hill, Eckhard Melcher, Robby Wegner, Ursula Wilken, Joachim Wittenzellner
published in European Journal of Wood and Wood Products , Vol. 78, pages 271 - 279, 2020
BAM, division Contaminant Transport and Environmental Technologies