Biosolids from a municipal sewage treatment plant were studied from the standpoint of partially characterizing the polar components in the matrix as well as targeting specific substances. Targeted analytes were determined byHPLC/fluorescence detection in some cases and confirmed through high resolution mass spectrometry (accurate mass determination) or both. The bacterial endpoints consisting of surfactants and products from surfactants were present as expected and were generally greater than mg/kg levels meaning that they could pose significant interferences to target analytes at low ïg/kg levels. Thus, one goal in characterization was to identify some of these major components as an aid in formulating cleanup strategies. Target analytes consisted of fluoroquinolone antibiotics. These occurred in the ïg/kg levels for some compounds. The target analytes and matrix characterization were further studied using accurate mass UPLC/TOF-MS which revealed many components containing polyethylene glycol moieties and a group of quartenary ammonium surfactants. Anionic components remain to be characterized more fully by UPLC/TOF-MS but some major components were identified using derivatization (trimethylsilylation) and GC/MS.