Accurate quantitative determination of monoaromatic compounds for the monitoring of bioremediation processes

This work demonstrated that the protocol for sample treatment, necessary to remove the microbial biomass prior to an analysis, is a critical issue for obtaining accurate results when volatile compounds are present. Two phenomena were observed, solute adsorption and stripping in the gas phase in contact with the liquid. It was demonstrated that the best protocol involved centrifugation using poly tetra fluoro ethylene (PTFE) capped tubes completely filled with the liquid suspension, i.e. without any gas phase inside it. This approach allowed a solute loss lower than 1%. The results also indicated that the optimum centrifugation conditions were 10000g at 10 °C for 10 min. Alternatively, it was found that the centrifugation technique developed could be used for the experimental determination of the activity coefficient of solubilized volatile compounds. This study additionally highlighted the fact that polyvinylidene fluoride micro filters (PVDF) and propylene GH polypro membranes (GHP) with a pore size of 0.45 μm could be used for biomass separation, although 10–12% monoaromatic adsorption by membrane was still present. In addition, a simple and sensitive method using high performance liquid chromatography (HPLC) with a UV detector set at the optimum point of 208 nm was developed for assessing the concentrations of BTX in samples taken from bioremediation processes. Minimum detection limits of 5, 4 and 10 μg L−1 were obtained for benzene, toluene and mixed xylenes, respectively.