Liquid water is described in two-state theory as mixture of localised molecular arrangements having different structure and density, the low-density (LDW) and high-density water (HDW). Theoretical calculations describe the formation of LDW and/or HDW domains, while their lifetime remains unknown. As ions partition selectively into LDW or HDW, modifying the water structuring, time-resolved photoinduced Delayed Luminescence (DL) of different salts solutions was measured. When formation of LDW domains is foreseen, significant DL signal was found, whose decay-time probability distribution is maximum in microsecond range. This result suggests the existence of such long lifetimes structures, which can participate in biological processes. (C) 2010 Elsevier B.V. All rights reserved.