Development and performance evaluation of extraction and purification procedures for halogenated DBPs in soil and lettuce.

Reuse of treated wastewater in agriculture exposes soils and edible crops to halogenated disinfection byproducts (DBPs), toxic compounds formed during chlorination. While DBPs are well characterized in water, analytical methods for soil and plant matrices remain scarce, limiting risk assessment for food safety and groundwater contamination. This gap hinders the implementation of EU Regulation 2020/741 on safe wastewater reuse. We developed and evaluated two solid-liquid extraction methods for 36 DBPs across 8 families (THMs, HANs, HNMs, HKs, HALs, HAcAms, HAs, and HAAs) in artificial/natural soils and lettuce, combined with pass-through SPE clean-up (ENVI-Carb for lettuce, Florisil for soils), to reduce matrix effects and enhance system stability and sensitivity. Extraction parameters (pH, ionic strength, and agitation/sonication time) were optimized using GC-ECD. HAAs were esterified prior to clean-up to avoid retention. Recovery rates ranged from 54.3-117.4% (29/36 analytes >80% for soil, 28/36 for lettuce), with method detection limits 14 times lower than prior work on lettuce (0.06-11.69 ng g-1 dry soil or fresh lettuce). The clean-up step was optimized using both GC-ECD (quantitative) and GC-MS (qualitative). Matrix effects were minimized, improving system robustness using the SPE approach. Stability tests revealed rapid degradation of HNMs, HALs, HANs and HKs in moist soils (<24 h) with halohydrins, HAcAms and HAAs identified as degradation products. This work provides sensitive, reliable tools for monitoring halogenated DBPs in agricultural soil/plant systems, supporting compliance with wastewater reuse regulations and addressing critical gaps in food safety risk assessment.