Portable automatic sensor for toxic gases

Abstract

A method is provided for the integration of a low-volume liquid flow and ing system and a portable optical waveguide-based fluorescence detector for the chemical analysis of reagents in fluorescence-based reactions. The method is particularly applicable to the detection of enzyme inhibitors, modifiers, or ligands in cases where a fluorescent enzyme substrate or product exists. In a preferred embodiment, the presence and concentration of acetylcholinesterase inhibitors, such as chemical warfare nerve agents or certain insecticides, is determined by mixing aqueous samples with a dilute solution of n-methyl indoxyl acetate, and monitoring the formation of a fluorescent product (n-methyl indoxyl). The presence of an acetylcholinesterase inhibitor reduces the amount of fluorescent product formed in a given time period. The reaction product passes through a flow cell in which it is excited by the evanescent wave produced by light as the light undergoes total internal reflection within an optical rod or fiber, or by light coming out the end-face of an optical fiber or rod.

What is claimed is: 
     
       1. A method for the analysis of an aqueous sample for the presence of acetylcholinesterase inhibitors consisting essentially of simultaneously: monitoring the presence and concentration of an acetylcholinesterase inhibitor by measuring the fluorescence of a chemical in an acetylcholinesterase-mediated reaction;   carrying out the reaction in an automated reagent flow and mixing apparatus with small volumes of reagents; and   measuring the concentration of said chemical in solution by an optical fiber or rod through which the emitted fluorescent light travels to an optical detector.   
     
     
       2. The method of claim 1 wherein said chemical is a product of the reaction. 
     
     
       3. The method of claim 1 wherein said chemical is a reactant of said acetylcholinesterase-mediated reaction. 
     
     
       4. The method of claim 1 wherein said reaction occurs in said apparatus. 
     
     
       5. The method of claim 1 wherein said reaction occurs on the surface of an optical fiber of said apparatus. 
     
     
       6. The method of claim 5 wherein said reaction occurs adjacent to said surface of said fiber.