Planar microfluidic devices and selective detection in gas chromatography : techniques and applications

This graduate research work addresses current techniques and method developments in gas chromatography. The two major themes of the work are to enhance the chromatographic performance and reliability of contemporary capillary column chromatography with the use of planar microfluidic devices, and to garner the power rendered by selective detectors such as micromachined differential ion mobility detection for the improvement of chromatographic aspects related to the portability, selectivity, sensitivity, and throughput of analytical systems. Included in this work are innovative analytical methods developed and successfully implemented to address difficult, unmet, and unarticulated chromatographic needs that have been encountered by the community of practice, particularly in the petrochemical and chemical industries. Over the course of the development of gas chromatography as a technique, many useful analytical approaches were developed to take advantage of the availability of hundreds of packing materials employed as stationary phases. However, the tools and devices designed for the use in column connectivity for the packed column era are not purposely meant for contemporary capillary column technology. Unfortunately, reliable options are few and far between. Recent advances in metallurgy, metal injection molding, deactivation chemistry, laser etching, and diffusion bonding techniques have resulted in the availability of planar microfluidic devices with features such as built-in fluidic gates, leak-free durability, improved inertness, in-oven and non-contact switching. Therefore, planar microfluidics becomes an important area of research in chromatography. In this work, the important tactical and strategic use of the aforementioned devices in capillary gas chromatography was realized with multiple chromatographic system configurations developed. The use of the device(s) for multi-dimensional gas chromatography, for hyphenated techniques, epitomized by a unified 1D/2D analytical configuration and two-dimensional gas chromatography ‚Äö- mass spectrometry were attained. When properly applied, selective detection can substantially ease the burden of separation traditionally imposed on the analytical column especially when the matrices of the samples are increasingly complex to tackle. Selective detection is an enabler to high-speed gas chromatography which is a key component in the development of portable and hand-held analytical devices. Therefore, research conducted in this field is not only important but critical to the capability of and sustainable development for gas chromatography as a technique. In the current research, the performance, benefit, and impact of using differential ion mobility spectrometry with resistively heated temperature programmable micromachined gas chromatography is investigated and its usefulness highlighted. The synergy of hyphenated techniques with other contemporary selective detectors such as the pulsed sulfur chemiluminescence detector and mass spectrometry detector operating in selected ion monitoring mode are also reaffirmed and illustrated in challenging industrial applications.