Evaluating factors affecting the sample processing for trace analysis of organophosphate tri- and di-esters in seawater: Application in the Loire estuary (France).

Organophosphate esters (OPE) are high production volume chemicals largely used as plastic additives, which are widely distributed in the marine environment. In this study, a design of experiments (DoE) approach was used to assess the major factors affecting the performance of a sample treatment workflow for the simultaneous trace analysis of 19 organophosphate triesters (tri-OPEs) and 6 degradation metabolites, organophosphate diesters (di-OPEs), in seawater samples. The influence of key factors in the recovery rate of each target compound was evaluated. HLB cartridges were selected as the best option for the majority of compounds in a workflow which also includes an acid washing step of the SPE column followed by a basified methanol first elution and a second elution with ethyl acetate. The method developed was validated in terms of accuracy (51-125 %), precision (1-21 %RSD), detection (0.0058-1.7 ng/L) and quantification (0.014-4.4 ng/L) limits and then applied to study the OPE occurrence in seawater from the Loire estuary (north-west France). Obtained results revealed differential pollution profiles and levels, generally in line with the anthropogenic pressures present in the area. Concentrations ranged 18-100 ng/L for ∑19tri-OPEs and 1.7-56.6 ng/L for ∑6di-OPE. TCIPP showed the highest concentrations among studied OPEs (up to 45 ng/L in the most polluted site). TEP, Tn/iBP, TCEP and DPhP also showed a ubiquitous presence in the area. The developed workflow allowed a faster and simultaneous study of both tri-/di-OPEs, becoming a useful analytical tool for monitoring these plastic additives in marine environments.