The Carboxen-PDMS fiber is a bi-polar fiber, possessing both adsorption and absorption mechanisms. While benzene falls within the molecular weight range of the fiber, overload can result in peak tailing. The linear range for C2-C10 hydrocarbons of this fiber is approximately 10ppb-10PPM.
To address this, it is advisable to increase the temperature of the injection port (i.e., 290-300 oC) to enhance the desorption of benzene from the fiber, thereby improving the peak shape. Furthermore, consider using a different column type that can withstand higher temperatures than a 624 phase, allowing the inlet temperature to be raised to more effectively drive benzene off the fiber.
To optimize the sample preparation process, it is recommended to use salt (i.e., 0.5 -1 g NaCl) to increase the analyte in the Headspace (HS). Additionally, using an Inlet Liner, Direct (SPME) Type, Straight Design (unpacked) can also improve peak shape.