FACILITATED CATECHOLAMINE TRANSPORT THROUGH BULK AND POLYMER-SUPPORTED LIQUID MEMBRANES

A series of crown boronic acids, 1-4, were synthesized and studied as carriers for catecholamine transport through bulk liquid membranes (BL Ms) and supported liquid membranes (SLMs). Carrier 1 greatly facilitat ed the transport of primary catecholamines through BLMs; whereas, the more lipophilic analogues 3 and 4 were less effective. A combination o f kinetic, mass spectral, and NMR evidence suggests that the transport ed species in BLMs is the cyclic, zwitterionic, 1:1 complex 7. The SLM transport studies used a liquid membrane of 2-nitrophenyl octyl ether supported by a thin, flat sheet of porous polypropylene. In the absen ce of carrier there was neglible dopamine transport (<5 x 10(-9) mol/m (2) . s) at pH 7.2. When the membrane contained carrier 3 (33 mM or ab out 2% wt), facilitated catecholamine transport was observed in the or der of dopamine (5 x 10(-7) mol/m(2) . s) > epinephrine (1.5 x 10(-7) mol/m . s) > norepinephrine (0.8 x 10(-7) mol/m(2) . s). SLMs containi ng carrier 3 were stable, implying that carrier 3 is a very good candi date for transport mechanism studies. Crown boronic acid 4 was an even better transport carrier of primary catecholamines with a transport o rder of norepinephrine (4.7 x 10(-6) mol/m(2) . s) > dopamine (3.5 x 1 0(-6) mol/m(2) . s) much greater than epinephrine (3 x 10(-8) mol/m(2) . s). It is 10 times more effective than an equimolar mixture of boro nic acid 5 and crown 6, which is one of best examples of ditopic coope rativity yet observed in SLM transport. SLMs containing 4, however, di d not exibit long-term stability. Overall, it is possible that a devic e based on SLMs containing crown boronic acid carriers can be develope d to selectively extract catecholamines from clinical samples.