Stabilized Liquid Membrane Device (SLMD) for Passive, Integrative Sampling of Bioavailable Metals in Water

The SLMD (U.S. patent no. 6,296,760) is a passive, integrative sampler that provides an alternative or complementary approach to conventional water sampling for trace metals. A water-insoluble organic complexing mixture diffuses in a controlled manner to the exterior surface of the sampler membrane (Figure 1), which provides for continuous sequestration of labile (bioavailable) forms of trace metals including cadmium (Cd), cobalt (Co), copper (Cu), nickel (Ni), lead (Pb), and zinc (Zn) for up to several weeks. In-situ deployment of SLMDs in both “bare ” and “sheathed ” configurations (Figure 2) provides for a passive, time-integrated analogue of unfiltered and filtered samples. The SLMD can also be utilized for in-laboratory preconcentration and speciation of labile trace metals from grab water samples. The advantage of the SLMD for detecting transient pulses of metals has been demostrated by field studies conducted in Missour