POTENTIOMETRIC, ENANTIOSELECTIVE SENSORS FOR ALKYL AND ARYL AMMONIUM-IONS OF PHARMACEUTICAL SIGNIFICANCE, BASED ON LIPOPHILIC CYCLODEXTRINS

Lipophilic alpha, beta and gamma cyclodextrins (CDs) have been systematically analysed in order to establish their selective binding to onium ions. They have been identified as excellent ionophores for a range of ions of vital importance in clinical, pharmaceutical and forensic analysis. From the results obtained we found the following. A peroctylated cyclodextrin provides a size-selective cavity for the binding and detection of onium ions. Potentiometric alpha, beta and gamma cyclodextrin-based electrodes selectively sense NH4+, NMe(4)(+) and NEt(4)(+) ions respectively. These experiments were performed in order to enable us to understand the nature of analyte recognition by the lipophilic cyclodextrins. Peroctylated alpha CD is a suitable ionophore for dopamine hydrochloride, - log [C] = 5.4, - log K = 2.0 (in serum level of Na+, K+, Ca2+) whereas peroctylated and 2,6 didodecyl beta CD sense acetylcholine chloride, - log[C] = 5.0, - log K = 4.2 (in serum level of Na+, K+, Ca2+) and creatinine hydrochloride, - log K = 2.7 (in serum level of Na+, K+, Ca2+), respectively. The 2,6 didodecyl beta CD responds to more bulky aryl ammonium ions such as the anaesthetics procaine, prilocaine and lignocaine hydrochlorides, - log K = 4.2 (in serum level of Na+, K+, Ca2+). Partially octylated alpha CD has been identified as an enantioselective sensor for ephedrine hydrochloride, - log K = 4.5 (in serum level of Na+, K+, Ca2+), - log K-+/-(pot) = 2.6, and related compounds such as amphetamine hydrochloride. The 2,6 didodecyl beta CD is enantioselective for propranalol hydrochloride, - log K = 4.2 (in serum level of Na+, K+, Ca2+), - log K-+/-(pot) = 2.7. Complexation has also been studied by electrospray mass spectrometry (ESMS).