BIOSENSORS BASED ON BILAYER-LIPID MEMBRANES FOR AUTOMATED CONTINUOUS MONITORING OR RAPID SCREENING OF ENVIRONMENTAL-POLLUTANTS

This report describes applications of bilayer lipid membranes (BLMs) i n the automated continuous monitoring or rapid screening fin a single format) of environmental pollutants. Filter-supported BLMs were used f or the electrochemical pow-injection analysis (FIA) of triazine herbic ides (simazine, atrazine, and propazine). A continuous flow mode was u sed and injections of herbicides were made into flowing streams of a c arrier electrolyte solution. A transient current signal (with a magnit ude related to the herbicide concentration) reproducibly appeared in l ess than 2 minutes after exposure of the lipid membranes to the herbic ides and increased in the order of simazine, atrazine, and propazine t hat allowed selective detection and analysis of these triazines in mix tures. The system is regenerable and can be used for repetitive cycles of injections. Self-assembled BLMs (s-BLMs) on metal supports were us ed for the rapid and sensitive electrochemical detection of above tria zine herbicides with detection limits on the order of ppb. Examples of uses of s-BLMs for the detection of gases such as NH3 (using gramicid in as ionophore) and of CO2 and cyanide ions (s-BLMs with incorporated hemoglobin or methemoglobin, respectively) are also provided herein. Electrochemical ion-current increases reproducibly appeared within sec ond(sl after exposure of the lipid membranes to the analyte of environ mental interest. The magnitude of the ion current was linearly related to the analyte concentration. The present minisensors have exhibited good mechanical stability and longevity (over 48 hours), and constant sensitivity and response to a given concentration of analyte in soluti on. The sensors can be simply and reliably fabricated at low cost and provide the advantages of fast response times (in the order of seconds ) to alterations of analyte concentration, low detection limits (ca. 1 0(-6) M for ammonium ions and ca. 10(-9) M for carbon dioxide, triazin es, or cyanide ions), and capability of analyzing small sample volumes . Results of interference studies are reported herein. (C) 1997 John W iley & Sons, Inc.