Per- and polyfluoroalkyl substances (PFAS) are persistent environmental contaminants known for their toxicity, mobility, and bioaccumulation. Efficient sample preparation and analysis of these compounds are critical for environmental monitoring. In this study, a novel analytical methodology is presented, integrating dynamic headspace extraction (DHS) and thermal desorption (TD) with one-dimensional (1D) and two-dimensional (2D) gas chromatography-time-of-flight mass spectrometry (GC-TOFMS) for the quantification of target volatile and semi-volatile PFAS. Such an approach also enables the non-targeted screening of other classes of contaminants in aqueous samples. The method was optimized and validated for nine (semi-)volatile PFAS, including fluorotelomer alcohols (FTOHs), acrylate (FTAc), and alkyl sulfonamides (FOSA, FOSE). Three types of adsorbent materials were evaluated during the enrichment step, among which Tenax TA demonstrated superior recovery and reproducibility. Extraction volumes of 1 L, 2 L, and 5 L were tested, with 1 L providing the most consistent recoveries and reproducibility. The optimized method achieved detection limits as low as 2.17 ng L-1, indicating high sensitivity. In a case study involving water from an industrial site, the enhanced separation and detection capabilities of GC×GC-TOFMS enabled the identification of 115 additional environmentally relevant compounds, including halogen-containing compounds, monoaromatics, and polycyclic aromatic hydrocarbons. This integrated DHS-TD-GC×GC-TOFMS approach provides a robust and suitable analytical solution for targeted PFAS monitoring, combining high sensitivity and selectivity with simultaneous non-targeted analytical capabilities - a particularly advantageous feature for the environmental monitoring of (semi-)volatile chemicals in real samples.