Go to one of the trade rags (http://www.eet.com) and search for 'chemical.'
you'll get a lot of results for this sort of sensor, ie:


1.Chemical sniffer relies on SAW-based technology

99% 2000/11/09 www.eet.com ORLANDO, FLA. . Sawtek Inc., through its
subsidiary Microsensor Systems Inc., has introduced the Hazmatcad
hazardous-material chemical agent detector, designed for hazardous-material
teams, federal agencies and military organizations. Package


2.Infrared lasers depict chemical bonds

99% 2000/11/11 www.eet.com An infrared laser experiment at the University of
Wisconsin has turned up a new way to create images of molecules and of the
bonds that hold them together. A laboratory setup at the university used a
pair of directed laser beams: one to stimulate vi


3.Cyrano's odor-sniffing chip will enable new breed of chemical analysis
  tools

95% 2000/11/11 www.eet.com PASADENA, Calif. ( ChipWire)- Cyrano Sciences
Inc. here is about to roll out a handheld chemical-analysis system built
around the company's proprietary Nose Chip, a sensor chip that can


4.Cyrano's system follows its nose

92% 2000/11/11 www.eet.com Cyrano Sciences Inc. is about to roll out a
handheld chemical-analysis system built around the company's proprietary
Nose Chip, a sensor chip that can smell.


5.Chemical sensor chip IDs tiny picoliter samples

91% 2000/11/14 www.eet.com University of Arkansas researchers have
demonstrated a sensor chip that harnesses semiconductor photolithography
equipment to pattern 2-micron-deep wells for identifying chemicals in
quantities as small as 1.2 picoliters.

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