A variety of degradation products are produced upon pretreatment of lignocellulosic biomass under different thermochemical conditions. Production and release of degradation products is affected by the concentration of solids initially present in the pretreatment reactions. Qualitative and quantitative interrogation of hydrolysates is also paramount to identifying potential correlations between pretreatment conditions and microbial inhibition in downstream bioconversion processes. 
Samples of poplar wood and corn stover were pretreated in batch mode with 0.7% H₂SO₄ for eight minutes at 180ºC. Concentration of initial solids tested included: 0.3%, 1%, 3% and 10%. Resulting pretreatment liquids were then filtered, extracted with MTBE and analyzed by LC-PDA-MS/MS (liquid chromatography-photodiode array-tandem mass spectrometry). Compounds quantified include aromatic acids, aliphatic acids, aldehydes and phenolic degradation products. The influence of initial solids concentration on product accumulations are presented.