A novel injection technique for high-speed gas chromatography is demonstrated. Synchronized dual-valve injection is shown to provide peak widths as low as 1.5 ms (width at half-height) for an unretained analyte. This was achieved using a 0.5-m DB-5 column with an internal diameter of 100 μm and a film thickness of 0.4 μm operated at a temperature of 150 °C with a column absolute head pressure of 85 psi, resulting in a dead time of only to = 26 ms (∼1900 cm/s, 26 mL/min). Using the DB-5 column in a 1-m length under the same instrumental parameters, with a resulting linear flow velocity of 935 cm/s (12.7 mL/min, to = 117 ms), a minimum peak width of 3.3 ms was obtained. During an isothermal separation, 10 analytes were separated in a time window of 400 ms. A rigorous comparison of experimental and theoretical band-broadening data based on the Golay equation showed that band broadening is limited almost entirely by the chromatographic band broadening terms expressed by the Golay equation and not by extra column band broadening due to the injection process. Synchronized dual-valve injection offers a rugged and inexpensive design, providing extremely reproducible injections with peak height precision of 2.4% (RSD) and low run-to-run variation in retention times, with an average standard deviation less than 0.1 ms. Herein, synchronized dual-valve injection is demonstrated as a proof of principle using high-speed diaphragm valves. It is foreseen that the injection technique could be readily implemented using a combination of thermal modulation and high-speed valve hardware, thus optimizing the mass transfer and not significantly sacrificing the limit of detection performance for high-speed GC. Further implications are that, if properly implemented, high-speed temperature programming coupled with this new technology should lead to very large peak capacities for ∼1-s separations.
The recent COVID-19 pandemic and the prospect of future global pandemics highlight the long-standing need to passively eliminate viruses and bacteria on surfaces. Conventional antimicrobial surfaces and coatings are typically constrained by a trade-off between antimicrobial efficacy and physical durability. A biphasic polyurethane coating has been developed that breaks this trade-off by incorporating a durability-imparting polycarbonate (PC) discrete phase with a continuous poly(ethylene glycol) (PEG) transport phase that absorbs, stores, and releases antimicrobial active compounds for extended microbial inactivation. The biphasic polymer was shown to absorb carboxylic acid and quaternary ammonium antimicrobial active compounds, maintained their levels after five years of simulated cleaning, and inactivated up to 99.99% of Human Coronavirus 229E and Influenza A H1N1. Furthermore, the levels of antimicrobial active compounds on the biphasic coating could be augmented by cleaning the substrate with a disinfectant. The practicality of biphasic coatings for automotive and commercial aerospace environments was demonstrated by showing control of hardness and stain resistance through biphasic composition, showing environmental durability through heat, humidity, and light exposure, and passing flammability protocols.
Since its introduction over 60 years ago, gas chromatography (GC) has become a cornerstone technique of analytical chemistry. While the basic components of a GC instrument have not changed since its introduction by Martin and James in 1952, instrumentation refinement has answered demands for faster, more sensitive and selective separations of complex samples. This review will discuss the advances made in GC instrumentation within the past few years as found in the literature, granted patents and commercial advances. The revival of older instrumentation techniques for current applications will also be discussed. Hardware advances discussed include new injection techniques, advances in heating technology (including resistive heating and two source heating for GC ovens) , with the largest volume of work being done in the development of new detectors. A brief discussion on commercially available portable GCs is also included. Advances in the realm of column technology, such as commercialization of high temperature silica capillaries and stationary phases stable to 480°C, are also discussed. Novel GC stationary phase development has incorporated such materials as sol-gel poly(ethylene glycol), nanoparticles, ionic liquids, and co-polymers. Stationary phases are also discussed in relation to microfabricated GC, i.e. chip-based GC. The extensive work being completed in μGC is discussed herein, including column interfacial components for rapid heating, as well as sensitive and selective detection. Keywords: gas chromatography, analytical instrumentation, hardware advances
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