ONLINE MONITORING OF HYDROPHOBIC COMPOUNDS AT SELF-ASSEMBLED MONOLAYER MODIFIED AMPEROMETRIC FLOW DETECTORS

Substantial improvements in the selectivity of amperometric monitoring of flowing streams are obtained by using detectors coated with neutra l n-alkanethiol monolayers. Permselective transport properties, based on solute polarity, are obtained and add a new dimension of informatio n to amperometric detection. An elegant way of varying the transport p roperties of hydrophobic drugs and the exclusion of hydrophilic compou nds is achieved by varying the chain length (i.e., hydrophobicity) of the n-alkanethiol modifier. The dynamic behavior of the detector is ev aluated with respect to the thiol chain length or concentration, flow rate, solute concentration, and other variables. The surface coating, and hence the discriminative properties, are highly stable under the v igorous hydrodynamic conditions existing in the flow cell. Highly sele ctive flow injection measurements of chlorpromazine in an untreated ur ine sample are illustrated.