Ion exchange resins used to polish UPW are a major source of dissolved particle precursors, many of which are aromatic and optically active. This presentation introduces absorbance-transmittance excitation-emission matrix (A-TEEM) spectroscopy for measuring these resin leachates and compares the results with CPC, TOC, and high-resolution FT-ICR mass spectrometry. It shows that A-TEEM can quantify and speciate leachates in seconds to minutes at ppb sensitivity, making it suitable for laboratory, at-line, and potential continuous monitoring.