Partially Buried Microcolumns for Micro Gas Analyzers

• Published in: Analytical chemistry (Washington) 2009-05, Vol.81 (9), p.3471-3477
• Main Authors: Radadia, Adarsh D, Morgan, Robert D, Masel, Richard I, Shannon, Mark A
• Format: Article
• Language: English
• Subjects: Analytical chemistry; Chemistry; Chromatographic methods and physical methods associated with chromatography; Chromatography; Chromatography, Gas - instrumentation; Comparative analysis; Exact sciences and technology; Feasibility Studies; Gas chromatographic methods; Microtechnology; Other chromatographic methods; Temperature; Time Factors
• ISSN: 0003-2700; 1520-6882
• DOI: 10.1021/ac8027382

This article demonstrates the feasibility of making a partially buried micro gas chromatography (μ-GC) column with a rounded channel wall profile, which enables coating the stationary phase more uniformly and shows better separation characteristics than a square deep reactive ion etched (DRIE) wall profile. A buried structure fabrication method was adapted to fabricate 34 cm long, 165 μm wide, and 65 μm deep partially buried microcolumns, which had a unique rounded microcolumn wall profile similar to that of a flattened circular tube. The separation characteristics were compared to that of a 34 cm long, 100 μm × 100 μm square DRIE microcolumn, which had a similar hydraulic diameter. Minimum height equivalent to a theoretical plate (HETP) and reduced HETP of 0.39 mm and 6.02, respectively, with a retention factor of 6.3 were obtained on the coated partially buried microcolumn compared to 0.66 mm and 6.73, respectively, on the coated square DRIE microcolumn with a similar retention factor. The partially buried microcolumn was found to perform closer to the theoretical approximation and this could be attributed to the uniform phase deposition in the partially buried microcolumn compared to the square DRIE microcolumn. A 10 component mix was separated on the partially buried microcolumn in 3.8 s with the maximum peak width at half-height equal to 0.2 s, while a similar mix separated at higher pressure and temperature conditions on the square DRIE microcolumn in 4.6 s. The rounded corners allowed depositing thinner stationary phase, which was reflected in the faster elution of n-C 12 on the partially buried microcolumn compared to the square DRIE microcolumn. The better performance of the partially buried microcolumn may be attributed to either the rounded channel wall profile, the clean channel structures produced by the fabrication process, or the double-etched wall profile, which lowers the Taylor-Aris dispersion.