The determination of quaternary ammonium compounds (QAC) by means of a 2-phase-titration or photometry is a well established procedure for the quantification of cationic detergents in aqueous solutions. It is known that this analytical principle can also be used for the measurement of QAC extracted from treated timber. However only few information are available concerning the reproducibility or the recovery rate of this procedure. In order to validate the whole technique an extended ring test was performed by 8 participants. Impregnated milled spruce with a QAC content of 1000mg/kg was distributed between the partners in a first stage. In a second step milled spruce with an “unknown” lower concentration (220mg/kg) and finally impregnated EN 113 test specimens (3-4kg QAC/m³) were investigated. The sample preparation, the extraction of QAC as well as the quantitative determination were performed according to standard or “in house” procedures. The analytical procedures were used successfully for the quantification of QAC in treated timber ranging from 200 to 1000mg/kg. Furthermore it could be shown that in general the recovery rate varies between ± 5% independent of the analytical method used whereby a higher deviation was found for material with a low QAC content. It was also to be seen that the extraction procedure is by far the most important factor of the analysis.

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