Evaluation of Tenax TA thin films as adsorbent material for micro preconcentration applications

The purpose of this research was to evaluate Tenax TA in the form of thin films as an adsorbent material for micro preconcentration applications. The micro preconcentrator (μPC) consists of embedded high-aspect-ratio three-dimensional (3D) micro pillars coated with an adsorbent polymer. The silicon-glass die has outer dimensions of 7 mm × 7 mm, total inner surface area of ∼ 10 m2/g, and a total inner volume of ∼ 6.5 μL. The μPC has on-chip thermal desorption capability and comprises more than 3500 micro pillars with dimensions of 30 μm × 120 μm × 240 μm. It was found that the surface area of Tenax TA films varies with the solution's concentration. The lower concentration solutions produced films with larger surface area. Three modes of analyte uptake by the polymeric adsorbents were investigated. Experimental results showed that crystal-void-filling is the dominant mode of adsorption in Tenax TA as opposed to solid-phase dissolution and pore-filling modes. Representative VOC samples such as alkanes, ketones, and alcohols were used to compare the adsorption of Tenax TA films. With the exception of hexane, the adsorption efficiency of Tenax TA films for the VOCs tested was greater than 99.5%. The results showed that there is no difference in the adsorption properties between beads and films of the adsorbent polymer.