Several flow-cell radiation detector systems are commercially available for quantification of aqueous radioactive solutions. These systems do not use the technique of pulse shape discrimination to identify the incident radiation and therefore are limited in environmental characterization application when coupled to an ion chromatography system. The advantages of the pulse shape discriminating flow-cell detector over the commercially available systems include: (1) lower minimum detectable activity for alpha radiation, (2) reduced radiological interferences that may exist between co-eluted alpha- and beta-emitting radionuclides, and (3) possible isotopic information from the ion chromatography system. For Tasks 1.1.1 and 1.1.2 of this project, several scintillation materials were investigated for pulse shape (alpha and beta) discrimination capabilities and the best candidate material was optimized. In addition, the following detector properties were also optimized: scintillator particle size, flow-cell tubing type, and electromagnetic as well as optical crosstalk between the photomultiplier tubes.