An LC‑MS/MS method addressing the volatility challenge for trace analysis of halogenated phenols and their structurally related analogs in wastewater.

Abstract

Halogenated phenols (HPs) and their transformation products are frequently detected in wastewater and sludge, but accurate determination remains challenging because analyte volatility can cause significant losses during sample preparation and instrumental analysis. In this study, a solid-phase extraction coupled with liquid chromatography-tandem mass spectrometry (SPE-LC-MS/MS) method was developed for the simultaneous determination of 12 halogenated phenols and structurally related compounds in wastewater and sludge. Method optimization focused on minimizing volatility-induced losses by controlling solvent evaporation, reducing ion source temperatures, optimizing extraction/elution conditions, and avoiding freeze-drying during sludge pretreatment. Correlation analysis revealed that volatilization rather than thermal degradation dominated analyte loss, and compounds with saturated vapor pressure above 0.001 Pa were particularly susceptible to volatility effects. The optimized method exhibited good linearity (R² ≥ 0.99), low detection limits (0.01-3.51 ng/L for water and 0.01-1.63 ng/g for sludge), satisfactory recoveries (64.1-130.3%), and good precision. Application to a municipal wastewater treatment plant revealed para-chloro-meta-xylenol (PCMX) as the predominant contaminant, while its dimeric products, di-PCMX-1 and di-PCMX-2, were identified in wastewater treatment processes for the first time. These dimers persisted in effluent and sludge despite efficient removal of most parent HPs, suggesting their formation during wastewater treatment. The proposed method provides a reliable analytical approach for monitoring halogenated phenols and their transformation products in environmental matrices.