Challenges in the Analyses of Organophosphate Esters

Organophosphate esters (OPEs) have been subject to considerable scientific and public scrutiny in recent years. The combination of their physicochemical characteristics and lack of standard analytical methods has resulted in growing concerns with respect to the validity of OPE concentrations reported in the literature. The goal of this study was to address the analytical challenges in analyses of OPEs by comparing the precision and accuracy of data generated for individual target analytes by different laboratories. Eleven international research laboratories were recruited in this study, and a total of 16 OPEs, chosen among the most frequently reported ones, were targeted. Results demonstrate the participating laboratories had generally good to very good consistency for the suite of OPEs analyzed, but accuracy was found to be a problem for several OPEs and laboratories. Methods utilized for the quantification of tri-m-tolyl phosphate, tri-p-tolyl phosphate, and tris(2butoxyethyl) phosphate performed worst overall, as highlighted by their zeta-scores, suggesting that interpretation and comparison of results for these OPEs should be made with caution and that current analytical methods may need to be improved. Liquid chromatography and tandem mass spectrometry performed best for both precision and accuracy.