A simple and rapid capillary electrophoresis method with capacitively coupled contactless conductivity detection (CE-(CD)-D-4) for the simultaneous determination of inorganic and organic anions in liquid product obtained from the hydrothermal treatment of biomass residues is presented. Under the optimal analytical conditions, limits of detection ranged from 1.8 to 9.4 mu M for most target solutes and 53 mu M for citrate. Relative standard deviations were below 0.5% for migration times and within 0.6-6.5% for peak areas for all solutes. The proposed method was successfully applied for the rapid determination and screening of inorganic and organic anions in liquid product produced following differing hydrothermal treatment temperatures for banana and pineapple biomass, and the contribution of organic acid formation to acidity in the liquid was evaluated. CE-(CD)-D-4 could be a suitable method for the optimization or tailoring of HTT conditions for desired liquid product composition, and additionally for determination of the best variety(s) of biomass to use in such processes.