Functionalized Metal Oxides As A Stationary Phase And A Surface Template For Micro Gas Chromatography Separation Columns

Abstract

The present invention provides a detector and method for detecting substances in complex mixtures. The detector includes a microfabricated preconcentrator, a separation column with an on-chip thermal conductivity detector, a controller for controlling flow and thermal management and a user interface. The thermal conductivity detector includes a first resistor located at an inlet of the separation column and a second resistor located at an outlet of the separation column.

What is claimed is: 
     
         1 . A method of fabricating a separation column for use with a gas chromatograph, comprising:
 depositing a metal oxide by atomic layer deposition to create a stationary phase medium on said separation column.   
     
     
         2 . The method of  claim 1  wherein said metal oxide is aluminum oxide. 
     
     
         3 . The method of  claim 3  wherein said aluminum oxide is deposited as a plurality of layers with each layer deposited in a cycle comprising (a) exposure to trimethylaluminum (b) purge (c) exposure to water (d) and purge. 
     
     
         4 . The method of  claim 3  wherein each cycle deposits a layer of about 1-2 angstroms. 
     
     
         5 . The method of  claim 2  wherein said aluminum oxide is functionalized by exposure to silane. 
     
     
         6 . The method of  claim 5  wherein said silane is an alkylsilane. 
     
     
         7 . The method of  claim 6  wherein said silane is chlorodimethyloctadecylsilane. 
     
     
         8 . The method of  claim 2  wherein said aluminum oxide is functionalized by exposure to a plurality of silanes. 
     
     
         9 . A detector comprising:
 a micro-purge extractor in communication with a micro-scale gas chromatography column for the extraction and analysis of water organic compounds from an aqueous sample;   said micro-purge extractor having a cavity in communication with a sample inlet port, a purge gas inlet port, a waste outlet port and a purged water organic compound outlet port;   said sample inlet port adapted to receive an aqueous sample;   said purge gas inlet port, spaced apart from said sample inlet port, and adapted to receive inert gas which is used to purge water organic compounds from said cavity of said micro-purge extractor;   said waste outlet opposingly located from said purge outlet port, said waste outlet adapted for draining water from the chip;   said purge outlet in communication with a micro-thermal preconcentrator;   said micro-thermal preconcentrator adapted to adsorb and desorb water organic compounds;   at least one resistive heating element that when activated, causes said water organic compounds to be desorbed; and   said micro-scale gas chromatography column adapted to separate said water organic compounds and a micro-thermal conductivity detector for identifying said water organic compounds.   
     
     
         10 . The detector of  claim 9  wherein said separation column has an aluminum oxide stationary phase medium. 
     
     
         11 . The detector of  claim 10  wherein said aluminum oxide is functionalized by exposure to silane. 
     
     
         12 . The method of  claim 11  wherein said silane is an alkylsilane. 
     
     
         13 . The method of  claim 11  wherein said silane is chlorodimethyloctadecylsilane. 
     
     
         14 . The method of  claim 10  wherein said aluminum oxide is functionalized by exposure to a plurality of silanes. 
     
     
         15 . The detector of  claim 9  wherein said purge outlet port and said sample inlet port are located on a top side of said micro-purge extractor, said purge gas inlet is located on a side of said micro-purge extractor, and said waste outlet port is located on a bottom side of said micro-purge extractor. 
     
     
         16 . A detector for detecting hazardous air pollutants at parts-per-billion concentrations in complex mixtures comprising:
 a microfabricated preconcentrator;   a separation column with an on-chip thermal conductivity detector;   a controller for controlling flow and thermal management; and   a user interface.   
     
     
         17 . The detector of  claim 16  wherein said thermal conductivity detector includes a first resistor located at an inlet of said separation column and a second resistor located at an outlet of said separation column. 
     
     
         18 . The detector of  claim 16  wherein said separation column includes a medium comprised of silica a nanoparticle layer with a Tenax TA coating. 
     
     
         19 . The detector of  claim 16  wherein said separation column includes at least one channel that linearly decreases in width. 
     
     
         20 . The detector of  claim 16  wherein said separation column includes at least one channel that decreases in width in a stepwise fashion.