Standard-free kinetic calibration for rapid on-site analysis by solid-phase microextraction

In this study, a new calibration method, standard-free kinetic calibration, is proposed for rapid on-site analysis by solid-phase microextraction (SPME), based on the diffusion-controlled mass transfer model and equilibrium extraction. With this calibration method, all analytes can be directly calibrated with only two samplings. The feasibility of this calibration method was validated in a standard aqueous solution flow-through system and a standard gas flow-through system. The distribution coefficients of five polycyclic aromatic hydrocarbons (PAHs), including naphthalene, acenaphthene, fluorene, anthracene, and pyrene, between water and the PDMS fiber coating were determined and the concentrations of the PAHs in the flow-through system were successfully calibrated with the proposed standard-free calibration method. The extracted amounts of BTEX (benzene, toluene, ethylbezene, o-xylene) at equilibrium were also successfully calibrated with this method with two rapid sampling periods at 5 and 10 s. Compared with the previous calibration methods for rapid on-site analysis by SPME, this method does not require a standard to calibrate the extraction, nor does it require additional equipment to control or measure the flow velocity of the sample matrix. In addition, all of the extracted analytes can be quantified without considering whether the system reached equilibrium. The newly proposed standard-free kinetic calibration approach enriched the calibration methods available for on-site analysis by SPME.