High throughput direct analysis of water using solvothermal headspace desorption with porous thin films

Sample preparation has remained a bottleneck in analysis of biological and environmental samples. Thus, microextraction techniques to reduce time, cost, labor, and environmental impacts as compared to traditional solid phase or liquid-liquid extractions are appealing. In this work, a high throughput extraction method coupled with a novel desorption technique has been developed for the analysis of eight regulated PAHs in water. The targeted analytes were extracted by thin film microextraction (TFME) using single-use sorbents. The enriched analytes on thin films were directly introduced into a gas chromatography with a flame ionization detector (GC-FID) through solvothermal headspace desorption (ST-HD). The desorption of analytes was accelerated by adding a small volume of solvent into the headspace vial. The parameters that influence desorption, such as type and volume of solvent, oven temperature, and desorption time, were studied. As well, the key parameters (stirring rate, extraction time, and salt content) for TFME of PAHs from water were assessed and optimized. Reusability and durability of the film and background noise due to polymer decomposition were also assessed. The method was validated using standards in 3.5% aqueous NaCl. The limits of detection (LODs) were between 0.2 and 2.0 ng mL^-1, with linear ranges of 0.4-200.0 ng mL^-1 with R² > 0.99, and satisfactory accuracy and repeatability at three concentrations (low, mid, and high) within the linear range of the calibration curves. The calibration curves were also assessed for suitability as a matched matrix in the analysis of PAHs in a seawater sample. The technique was also applied for determination of PAHs in a produced water sample without the need for pretreatment and filtration of the sample. Although the complexity of produced water required the use of standard addition, we demonstrated that this approach is a useful tool for the analysis of complicated environmental samples.