Mitigating Matrix Effects in Groundwater: A Simple and Versatile Method for Quantifying Contaminants in Groundwater Using Online SPE-UHPLC-MS/MS

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This manuscript describes a novel and simple strategy for optimizing the determination of contaminants in groundwater using online solid-phase extraction (SPE) coupled with ultrahigh-performance liquid chromatography (UHPLC) and tandem mass spectrometry (MS/MS). The methodology optimization process considered several factors: analyte sorption in the syringe filter material, SPE conditions for effective cleanup, maximum injection volume, and spiking samples with additives to mitigate matrix effects. Matrix effects posed the greatest challenge, which was addressed by adding a few microliters of additives (citric acid and hydroxylamine) directly into the groundwater samples. This simple yet advantageous approach was also demonstrated with UHPLC coupled to high-resolution mass spectrometry without employing SPE. Under the optimized conditions, ten contaminants were evaluated, yielding excellent results at detected levels ranging from parts per billion (ppb) to parts per trillion (ppt), even without using isotopically labeled internal standards. These findings highlight the importance of investigating possible experimental issues that have a critical influence on the performance of analytical protocols. Finally, this work provides valuable insights for other researchers working on LC-MS/MS methods for determining organic contaminants in groundwater.