Performance comparison of straight circular and trapezoidal µGC columns for acetone–ethanol separation

This paper presents a comparative design and performance evaluation of two straight micro gas chromatography (µGC) columns with circular and trapezoidal cross-sectional geometries for the chromatographic separation of acetone and ethanol under identical operating conditions. Two geometries were simulated in a computational program, COMSOL Multiphysics, considering helium as a carrier gas and PEG (Polyethylene glycol) as a stationary phase. Parameters such as column length (10–100 cm) and hydraulic diameter (50–600 µm) were considered for both geometries and evaluated in terms of retention time, number of theoretical plates (N), resolution (R s ), and height equivalent to a theoretical plat (HETP). The findings show that there is a clear trade-off between efficiency and pressure drop for the two geometrical configurations considered. The straight column of circular cross section configuration results in lower efficiency, which can be noted from the lower theoretical plate number ranging from (0.5–3.9) × 10 3 plates, larger HETP value of 0.027–0.035 cm, and poor resolution R s < 1.25 at lower pressure drop (280–500) Pa and higher flow rate (approximately 0.5 m/s). However, the straight column of trapezoidal cross section shows better separation efficiency due to enhanced mass transfer, band broadening reduction, and a higher surface-to-volume ratio with better flow distribution. Though the performance is improved, this improvement is obtained at the expense of higher pressure drop (∼3.8 × 10 3 Pa) and lower flow rate (∼0.35 m/s). From the above considerations, it can be seen that the trapezoid shape is indeed a better geometry when compared to others in µGCs, especially when used for breath analysis.