Stabilized liquid membrane device (SLMD) for the passive, integrative sampling of labile metals in water

A stabilized liquid membrane device (SLMD) is described for potential use a s an in situ, passive, integrative sampler for cadmium (Cd), cobalt (Co), c opper (Cu), nickel (Ni), lead (Pb), and zinc (Zn) in natural waters. The SL MD (patent pending) consists of a 2.5-cm-wide by 15-cm-long strip of low-de nsity polyethylene (LDPE) layflat tubing containing 1 mL of an equal mixtur e (v/v) of oleic acid (cis-9-octadecenoic acid) and EMO-8Q (7-[4-ethyl-1-me thyloctyl]-8-quinolinol). The reagent mixture continuously diffuses to the exterior surface of the LDPE membrane, and provides for sequestration of se veral divalent metals for up to several weeks. Depending on sampler configu ration, concentration factors of several thousand can be realized for these metal ions after just a few days. In addition to in situ deployment, the S LMD may be useful for laboratory determination of labile metal species in g rab samples. Methods for minimizing the effects of water flow on the sampli ng rate are currently under investigation.