Precision of chlorophenols and chloroanisoles measurement in cooperage oak woods

This work was the first step of a study initiated by the FFT (Federation Francaise de la Tonnellerie) to review the different aspects of the oak wood contamination, and especially contamination by chlorophenols and chloroanisoles. This paper deals with the precision of chlorophenols and chloroanisoles measurement in cooperage oak woods. The analytical methods used were those developed and single validated by the 4 laboratories that did this work. Material was obtained by adding substances to sawdust and making dilution between supplemented sawdust and blank one. Thus, material was homogenous and has a theoretic level. Recovery values for chlorophenols were between 70% and 80%, except one, for the lowest PCP's level (theoretic 7.5 ng/g), which was 95%. For chloroanisoles, recovery values varied from 50% for the highest levels to more than 100% for the lowest levels. Measured reproducibility, expressed in variation coefficient of the standard deviation, was about 25% for TCP and PCP, 45% for TeCP, TCA and TeCA and more than 50% for PCA. For TCP, PCP, TCA and TeCA, despite the use of different methods, these values are of the same order as those given by the Horwitz formula. These values may help to compare results and to build a decision rule of the conformity of the oak wood. The heterogeneousness of the material is another source of the final result variability. This last source was not quantified in this work.