A high-throughput screening technique, developed earlier1 for reaction systems with primarily gaseous products, has been extended with quantitative and qualitative analysis of condensed reaction products. The technique is based on catalytically inert quartz capillaries (2 mm internal diameter) as microreactors, which allows for cheap and safe experimentation. To validate the technique, hydrothermal conversion (T 350 °C, P 200 bar) of beech wood and model compounds was used. Separation and sample preparation methods have been developed to recover the condensed reaction products. These methods, combined with the chemical analysis techniques, have shown to be accurate with respect to product recovery and detecting trends in the yield and composition of the products as a function of the operating conditions.