A stamped aluminium gas chromatographic column disk employing directly grown anodic aluminium oxide stationary phase for the separation of aromatic and chlorinated compounds.

In this study, mesoporous anodic aluminium oxide (AAO) with moderate polarity was used as a GC stationary phase to demonstrate the applicability to various compound species. The fluidic channel measured 6 meters in length and had a cross-section area of 0.127 mm2. The column disk measured 6.2 cm in diameter and was fabricated through a stamping process on an aluminium substrate. The AAO stationary phase was directly grown on the aluminium substrate through an anodization process using oxalic acid as the electrolyte. The pore size of the AAO stationary phase was approximately 50-70 nm, with film thicknesses ranging from 6-20 µm. AAO based on oxalic acid exhibited significantly reduced surface polarity, making it suitable for separating polarizable and slightly polar compounds. The theoretical plate number for benzene had reached 1800 plates per meter, and for n-butane, it had reached 2500 plates per meter. A complex mixture of 16 compounds spanning alkanes, olefins, aromatics, and chlorinated hydrocarbons was effectively separated in 8 minutes with the temperature programmed to 200 °C.

Separation of C1-C15 Alkanes with a Disk-Shaped Aluminum Column Employing Mesoporous AAO as the Stationary Phase.

A new type of gas chromatographic (GC) column employing a mesoporous anodic aluminum oxide (AAO) layer as the stationary phase was developed. The gas fluidic channels were fabricated on both sides of an aluminum disk via a mechanical stamping process. The tops of the gas fluidic channels were sealed with a thick aluminum foil and a thin glass liner. The cross section of this fluidic channel is triangular in shape and consists of two aluminum surfaces and one glass surface. The diameter of the aluminum disk is 8.7 cm, and the length of the GC column is 6.0 m. The AAO layer was grown on the aluminum surface and had an average pore diameter of 50 nm and a specific surface area of 4.13 m2 g-1. The thickness of the AAO stationary phase ranged from 6-150 µm. Although thin AAO is insufficient for separating light alkanes, methane and ethane can be separated with a resolution of 4.25 using a 150 µm thick AAO stationary phase at room temperature in less than 100 s. C1 to C15 alkanes can be completely separated within 20 min when using a temperature program ramped from room temperature to 350 °C. Some limitations of this preliminary design, such as peak broadening probably arising from the triangular cross section, not yet being suitable for polar compounds, and the lack of a stationary phase on one-third of the column surface are discussed.