Colloidal and dissolved organic matter (DOM), present in many forms in water, can affect the transport, bioavailabity, and laboratory detection of organic contaminants. Contaminants of emerging concern (CECs) are broadly defined to include endocrine disrupting compounds, pharmaceuticals and personal care products present in the environment.  We studied DOM-CEC interactions with fourteen different CECs under defined conditions using liquid chromatography tandem mass spectrometry (LCMSMS) and fluorescence spectroscopy experiments. Organic matter was used in bulk and fractionated form. Direct infusion of DOM into the mass spectrometer during LC injections of CEC mixtures was used to quantify interference, or matrix effects, on the accurate measurement of CEC target analyte concentrations. Most target analytes suffered signal suppression, however fractionated DOM produced greater interferences on target analyte measurements compared to the effects from bulk DOM. Sorption and complexation of CECs by DOM was also quantified using incubation and equilibrium dialysis experiments followed by fluorescence quenching and LCMSMS measurements. Incubation experimental results indicate that multiple populations of DOM molecules from both fresh and treated wastewater sources are involved in weak complexation interactions with CECs. Equilibrium dialysis experimental results also indicate that CEC interactions with DOM are DOM-concentration dependent and that CEC log K_ow can predict CEC affinity for high molecular weight DOM. LCMSMS and excitation emission matrix data will be interpreted.