Both gas-phase and liquid-phase systems were evaluated for their potential application in continuous on-line high performance liquid chromatography (HPLC) detection of arsenic species in oil shale byproduct waters. Previous work on related building blocks was reviewed in detail and possible systems chosen for additional laboratory evaluation. The basic system proposed includes on-line arsine generation followed by continuous gas phase detection with a thermionic ionization detector (TID) operated in the nitrogen/phosphorus mode, or liquid-phase colorimetry with silver diethyldithiocarbamate/pyridine (AgDDTC) reagent. Detection limits were calculated for arsenic based on static tests. The TID was tested in conjunction with gas chromatography of triphenylarsine, yielding 0.1 ng/min As sensitivity. The arsine AgDDTC system calculation was 50 ng/mL. Either system was deemed feasible for application to fractional ppM-level arsenic species detection on-line in HPLC effluents even though on-line sensitivities could be poorer than those calculated from the static tests by an order of magnitude. 62 refs., 4 figs., 4 tabs.