DETERMINATION OF DRUG SUBSTANCES USING IO N-SELECTIVE ELECTRODES

The use of ion-selective electrodes for the determination of drug subs tances is reviewed. Although the primary emphasis is placed on drugs i n the field of forensic chemistry, for example, paraquat, methamphetam ine, amphetamine, and cocaine, other clinically important drugs such a s procainamide, bretylium, disopyramide, and salicylate, as well as se rotonin, a biogenic amine, are also discussed. Sensor membranes of the se ion-selective electrodes can be prepared by incorporating a lipophi lic ion-exchanger (or neutral carrier) and an appropriate membrane sol vent in a poly(vinyl chloride) membrane matrix. In many cases, the com bination of the ion-exchanger, sodium 3,5-bis(2-methoxyhexafluoro-2-pr opyl)phenyl]borate and the membrane solvent, 2-fluoro-2'-nitrodiphenyl ether afforded the most sensitive sensor membrane for drugs. In some cases, the choice of membrane solvent was important and tris(2-ethylhe xyl) phosphate, tricresyl phosphate, and tetrakis (2-ethylhexyl) pyrom ellitate became excellent membrane solvents for making sensor membrane s responding to serotonin, methamphetamine and cocaine, respectively. Neutral carriers may be useful to make highly selective electrodes to specific drugs, but have not been studied in detail. We discussed here amphetamine-selective and salicylate-selective electrodes using the n eutral carriers, dicyclohexano-18-crown-6 and heptyl-4-trifluoroacetyl -benzoate, respectively, as typical examples.