The two candidates for generic liquid membranes, DDMS:thymol (1:2) and 6methylcoumarin:thymol (1:2), were denoted as system A1 and A2 ("A" for Acid), respectively. As the next step, the final EME conditions for systems A1 and A2 were optimized. First, the final liquid membrane compositions were considered, specifically the addition of NPOE as a stabilizing component for increased robustness was evaluated. For both systems, 1 part NPOE was added to 2 parts of the original solvent. In system A1, addition of NPOE did not give any significant improvement in recovery or current during extraction, while system A2, on the other hand, doubled the recovery for several of the most hydrophobic analytes (Figure ) and yielded a minor reduction in extraction current. DDMS:Thymol (1:2) and [6-methylcoumarin:thymol (1:2)]:NPOE (2:1) were therefore selected as the final liquid membranes for A1 and A2, respectively. The improved recoveries for A2 may have resulted from the relatively weaker interactions provided by NPOE, thereby diminishing the trapping of hydrophobic analytes within the liquid membrane. Kamlet-Taft values for the final A2 mixture could not be determined due to high UV-absorbance of NPOE, but are expected to be similar to 6-methylcoumarin:thymol (1:2).