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

A stabilized liquid membrane device (SLMD) is described forpotential use as an in situ, passive, integrative samplerfor cadmium (Cd), cobalt (Co), copper (Cu), nickel (Ni), lead(Pb), and zinc (Zn) in natural waters. The SLMD (patent pending)consists of a 2.5-cm-wide by 15-cm-long strip of low-density polyethylene (LDPE) layflat tubing containing 1 mL of an equalmixture (v/v) of oleic acid (cis-9-octadecenoic acid) and EMO-8Q (7-4-ethyl-1-methyloctyl]-8-quinolinol). The reagentmixture continuously diffuses to the exterior surface of the LDPE membrane, and provides for sequestration of several divalent metals for up to several weeks. Depending on samplerconfiguration, concentration factors of several thousand canbe realized for these metal ions after just a few days. In addition to in situ deployment, the SLMD may be useful for laboratory determination of labile metal species in grab samples. Methods for minimizing the effects of water flow onthe sampling rate are currently under investigation.