Development and evaluation of sample preparation methods for the determination of organic micropollutants in soil samples utilizing GC-APCI-QToF MS

Soil pollution poses a serious threat to terrestrial ecosystems and human health, yet studies often focus on a handful of pollutant classes per study. Wide-scope methodologies are necessary to account for the complexity and diversity of the soil matrix and the organic micropollutant mixture of both known and novel compounds it may contain. Thus, to facilitate comprehensive monitoring of the organic micropollutant burden in soil with gas chromatography coupled with high-resolution mass spectrometry (GC-HRMS), three wide-scope methods were developed and compared: modified QuEChERS (mQuEChERS), Accelerated Solvent Extraction (ASE), and Ultrasonic Assisted Extraction (UAE). Comparison of the three methods and the final choice of the modified QuEChERS were achieved via an examination of the performance characteristics, such as the number of analytes detected, recoveries, matrix effect, and precision, through a smart validation scheme that encompassed 38 analytes belonging to diverse pollutant classes. The mQuEChERS method was then fully validated for the simultaneous quantification of 75 analytes, including pesticides, polycyclic aromatic hydrocarbons (PAHs), polychlorinated biphenyls (PCBs), polychlorinated naphthalenes (PCNs), and organochlorine pesticides (OCPs). The method's limits of detection (MLOD) ranged from 0.04 to 2.77 μg kg^-1 d.w. Linearity was demonstrated within a concentration range of 30 to 300 μg kg^-1 d.w. Recoveries ranged from 70 to 120%. Method precision was deemed optimal (RSD < 11%). As proof of concept, six soil samples from Greece were analyzed, with results indicative of potential temporal variations in pollutant concentration, underscoring the necessity for extensive monitoring campaigns employing GC-HRMS.