Effect of Thermal Desorption Kinetics on Vapor Injection Peak Irregularities by a Microscale Gas Chromatography Preconcentrator

摘要

Microscale gas chromatography ((mu)GC) is an emerging analytical technique for in situ analysis and on-site monitoring of volatile organic compounds (VOCs) in moderately complex mixtures. One of the critical subcomponents in a (mu)GC system is a microfabricated preconcentrator (mu-preconcentrator), which enables detection of compounds existing in indoor/ambient air at low ((approx)sub ppb) concentrations by enhancing their signals. The prevailing notion is that elution peak broadening and tailing phenomena resulting from undesirable conditions of a microfabricated separation column (mu-column) are the primary sources of poor chromatographic resolution. However, previous experimental results indicate that the resolution degradation still remains observed for a mu-column integrated with other (mu)GC subcomponents even after setting optimal separation conditions. In this work, we obtain the evidence that the unoptimized mu-preconcentrator vapor release/injection performance significantly contributes to decrease the fidelity of (mu)GC analysis using our state-of-the-art passive preconcentrator microdevice. The vapor release/injection performance is highly affected by the kinetics of the thermal desorption of compounds trapped in the microdevice. Decreasing the heating rate by 20percent from the optimal rate of 90 deg Cs~(-1) causes a 340percent increase in peak tailing as well as 70percent peak broadening (30percent peak height reduction) to the microscale vapor injection process.