A NEW ISFET DEVICE FOR COCAINE ANALYSIS

We have fabricated and characterized two new cocaine-sensitive ISFET d evices based on a PVC-sebacate membrane containing cocaine-reineckate or cocaine-tetraphenylborate as exchanger. Both the ISFET sensors disp lay a linearity range for cocaine hydrochloride between about 3X10(-6) and 2X10(-2) mol l(-1) and a fast response (less than or equal to 25 s), which remain almost the same in the pH range 3-7. For the cocaine- reineckate and cocaine-tetraphenylborate ISFETs, the slope values are -53.9 and -51.3 Delta mV/Delta log c (c=mol l(-1)), and the precision of the measurements, as 'pooled SD%' is 1.1 or 3.5, respectively. Sele ctivity coefficient values for several possible interferences have bee n determined and the application of these sensors to the analysis of a uthentic samples containing cocaine and other substances commonly asso ciated with it is also reported.