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) in the automated continuous monitoring or rapid screening fin a single format) of environmental pollutants. Filter-supported BLMs were used for the electrochemical pow-injection analysis (FIA) of triazine herbicides (simazine, atrazine, and propazine). A continuous flow mode was used and injections of herbicides were made into flowing streams of a carrier electrolyte solution. A transient current signal (with a magnitude related to the herbicide concentration) reproducibly appeared in less than 2 minutes after exposure of the lipid membranes to the herbicides and increased in the order of simazine, atrazine, and propazine that allowed selective detection and analysis of these triazines in mixtures. The system is regenerable and can be used for repetitive cycles of injections. Self-assembled BLMs (s-BLMs) on metal supports were used for the rapid and sensitive electrochemical detection of above triazine herbicides with detection limits on the order of ppb. Examples of uses of s-BLMs for the detection of gases such as NH3 (using gramicidin 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 second(sl after exposure of the lipid membranes to the analyte of environmental 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 solution. 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. 10(-6) M for ammonium ions and ca. 10(-9) M for carbon dioxide, triazines, or cyanide ions), and capability of analyzing small sample volumes. Results of interference studies are reported herein. (C) 1997 John Wiley & Sons, Inc.