A BOND GRAPH MODEL FOR THE SAMPLE EXTRACTION INJECTION SYSTEM OF A MICROSIZED GAS-CHROMATOGRAPHIC INSTRUMENT/

A bond graph model of the sample extraction/injection system of a prot otype portable gas chromatographic instrument has been developed. In a ddition to performing the same functions as current portable gas chrom atographs (GCs), the new generation of GC instruments is designed to p erform extraction of analytes from liquid and solid samples. The proto type instrument achieves these improvements by taking of advantage of microfabrication technologies and microprocessor control in the design . A novel sample extraction/injection module is essential to the impro ved performance of the portable instrument, which will include microfa bricated components such as inlets, interface chips, fluid channels, c ontrol valves, optimal heater/sensor combinations, and multiport conne ctors. In order to achieve the desired analytical performance, all of the major components are heated to 250 degrees C during different stag es of a sample analysis. Predicting the performance of the system in t his operating regime requires the modeling and analysis of system beha vior in two interacting energy domains, fluid and thermal. This articl e represents the first effort to understand the dynamic behavior of th e thermofluid aspect of micro-GC instruments and one of the first atte mpts to apply the widely-used bond graph technique to modeling and ana lysis of microsized thermofluid systems. Simulation results using the bond graph model closely match available experimental data, with diffe rences typically less than 10%. This demonstrates that fluid dynamic t heory for macroscale systems, and the bond graph method based on it, c an be readily applied to microscale systems with these dimensions. The bond graph method can be a useful computer-aided design tool for the development of a new generation of truly integrated micro-GC instrumen ts and sensors fabricated with micromachining technology. (C) 1996 Ame rican Institute of Physics.