Stainless-Steel Column for Robust, High-Temperature Microchip Gas Chromatography

This paper reports the first results of a robust, high-performance, stainless-steel microchip gas-chromatography (GC) column that is capable of analyzing complex real-world mixtures as well as operating at very high temperatures. Using a serpentine design, a 10 m column with an approximately semicircular cross-section with a 52 μm hydraulic diameter ( D_h) was produced in a 17 × 6.3 × 0.1 cm rectangular steel chip. The channels were produced using a multilayer-chemical-etch and diffusion-bonding process, and metal nuts were brazed onto the inlet and outlet ports allowing for column interfacing with ferrules and fused silica capillary tubing. After deactivating the metal surface, channels were statically coated with a ≈0.1 μm layer of 5% phenyl-1% vinyl-methylpolysiloxane (SE-54) stationary phase and cross-linked with dicumyl peroxide. By using n-tridecane ( n-C13) as a test analyte with a retention factor ( k) of 5, a total of 44 500 plates (≈4500 plates per meter) was obtained isothermally at 120 °C. The column was thermally stable to at least 350 °C, and rapid temperature programming (35 °C/min) was demonstrated for the boiling-point range from n-C5 to n-C44 (ASTM D2887 simulated-distillation standard). The column was also tested for separation of two complex mixtures: gasoline headspace and kerosene. These initial experiments demonstrate that the planar stainless-steel column with proper interfacing can be a viable alternative platform for portable, robust microchip GC that is capable of high-temperature operation for low-volatility-compound analysis.