Stabilized liquid membrane devices

[5] The first type of passive sampler made for use in the aqueous environment was the semipermeable membrane device (SPMD).

Most metals dissolved in the aqueous environment are present as any of several ionic, complex-ion, and organically bound states.

[2] The outer portion of a SLMD consists of a section of sealed, flat, semi-permeable polyethylene tubing.

Sealed inside this tubing is a 1:1 mixture of a hydrophobic metal complexing agent and a long chain organic acid.

[2] Oleic acid is commonly used as the other half of the 1:1 hydrophobic reagent mixture, as it readily forms calcium oleates in the aqueous sampling media.

[1][2] Variable water flow can alter the sampling rates of metals by SLMDs, making a time-averaged concentration difficult to determine.

The purpose of the sampling was to investigate potential causes of sublethal effects of young trout and loss of benthic biodiversity in the creek.