Wednesday, April 1, 2015

High Temp CNT Modified Colnatec QCM as a GC Detector

The QCM devices and measurement circuit that were used for this study were purchased from Colnatec LLC (Gilbert, AZ). Colnatec’s mass detectors are unique in that the sensors are capable of operation of up to 500 °C without the need of water cooling. Colnatec and others have developed temperature compensation algorithms that improve sensor stability at high temperatures. Also, special QCM discs for high temperature application were obtained from Colnatec LLC (Gilbert, AZ) and were used in this study when explicitly noted.

High Temperature Mass Detection Using a Carbon Nanotube Bilayer Modified Quartz Crystal Microbalance as a GC Detector
Marcel Benz*, Lauren Benz ‡, and Sanjay V. Patel †
† Seacoast Science, Inc., 2151 Las Palmas Drive, Suite C., Carlsbad, California 92011, United States
‡ Department of Chemistry and Biochemistry, University of San Diego, San Diego, California 92110, United States
Anal. Chem., 2015, 87 (5), pp 2779–2787

Abstract Image
A small, portable gas chromatograph (GC) was assembled for the trace detection of controlled substances using a novel quartz crystal microbalance sensor (QCM). The QCM crystal surface was modified with a variety of sorption materials to increase adsorption thereby amplifying mass detection. Single polymer thin film coatings increased the QCM response by 1–2 orders of magnitude, while operating at over 100 °C. Adding a layer of carbonaceous nanomaterial (graphene or carbon nanotubes) above such a film dramatically increased sensitivity by up to 3 orders of magnitude compared to uncoated crystals. Separation and detection of submicrogram quantities of controlled substances was carried out within minutes by employing a GC column and detector temperature ramp up to 220 °C. An additional 10-fold enhancement in sensitivity was achieved by mechanical abrasion of the sample swabs used in the sample introduction process. This study demonstrated a novel use of a polymer composite modified QCM as a chemical sensor at high temperatures


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