The DarkSide-50 experiment at the LNGS underground laboratory is using a dual-phase liquid argon TPC to search for particle dark matter. A recent analysis, based on the use of only the ionization signal from very low energy events, shows the potential of liquid argon to detect low-mass WIMPs (<10 GeV/c^2). The null result of this search is currently the world-leading exclusion limit on WIMP-nucleon cross sections for WIMPs with mass between 2 and 6 GeV/c^2. In this region, noble liquids experiments were expected to have only limited sensitivity due to the vanishing scintillation signal. I will discuss the details of this analysis and briefly address the requirements for a future improvement.