Understanding the movement and deposition of biocides in wood is a fundamental aspect of the supercritical wood impregnation process and a key issue in developing the process e.g. to handle wood of larger dimensions. Previous research on supercritical wood impregnation frequently reports of a biocide concentration gradient in impregnated samples i.e. a lower concentration of biocides in the core of the samples than nearer the surface. Researchers seldom comment on the reasons for the observed gradients, and the subject of biocide/wood interactions is generally overlooked. In this paper we investigate the interactions between wood and propiconazole in supercritical carbon dioxide and hypothesize that the reasons for the observed gradients is that wood has a chromatographic effect on the biocides as they move with the carbon dioxide through the wood matrix. The degree of interaction at different conditions is estimated by calculation of partition ratios.

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