Demonstrating the application of a liquid chromatography-mass spectrometry method for the determination of phthalate diesters in complex solid and liquid environmental samples.

Phthalate diesters are ubiquitous contaminants of concern, yet their reliable determination in complex environmental matrices remains analytically challenging due to low environmental concentrations, matrix interferences, and widespread background contamination. Here, we present a robust LC-MS/MS workflow for the simultaneous quantification of eleven low- and high-molecular weight phthalates across four contrasting matrices: surface water, landfill leachate, soils, and municipal solid wastes. Sample preparation was streamlined using ultrasonication or filtration followed by solid-phase extraction (SPE), providing recoveries of 70-98% without the need for derivatisation. The method delivered sub-ng L^-1 detection limits (as low as 0.2 ng L^-1) and high reproducibility (RSD <5%), while integrated contamination-control strategies, including delay columns and phthalate-free materials, enabled reliable trace analysis. Systematic evaluation of matrix effects confirmed robustness across diverse environmental samples. This method combines sensitivity, selectivity, and broad applicability, offering a practical platform for routine environmental monitoring of phthalates at trace levels.