Comparison of three analytical methods for cocaine analysis of illicit powders

A new cocaine-sensitive ISFET device based on a cocaine-reineckate ion-pair complex dispersed in a PVC-sebacate matrix has been fabricated. This sensor displays a linear range for cocaine hydrochloride between about 3 x 10(-6) and 2 x 10(-2) M and a fast response (less than or equal to 25 s), which remains almost constant over the pH range 3-7. The sensor has been applied to the analysis of authentic illicit powders containing cocaine hydrochloride and other substances commonly associated with it, or of cocaine free base (crack). Experimental results were compared with those obtained employing two more common instrumental methods of analysis: gas chromatography (GC), and UV absorption spectrometry (the latter applied directly or based on second derivative absorption spectroscopy). Good agreement was found between results obtained by ISFET and GC methods, while UV absorption spectrophotometry proved suitable only in the case of pure cocaine hydrochloride and free base, or in samples also containing lidocaine, but using second derivative absorption spectroscopy.