Liquid chromatography-electrospray–tandem mass spectrometry method for determination of organophosphate diesters in biotic samples including Great Lakes herring gull plasma

• Analytical method for organophosphate (OP) diesters was developed for biotic samples.
• Addition of acetic acid greatly increased extraction efficiency of OP diesters.
• High ionic strength buffer was chosen as eluent of OP diesters.
• LC-ESI(−)–MS/MS is more ideal for the analysis of non-halogenated OP diesters.
• Three OP diesters were in field-collected plasma samples of Great Lakes herring gulls.

Environmentally relevant organophosphate (OP) triester flame retardants are known to degrade to OP diester phosphoric acids. In this study, a quantitatively sensitive method was developed for OP diesters in biological samples of varying complexity, bovine serum, chicken egg homogenate and pork liver. Fortified with 1 ng or 10 ng each of the six OP diester and six OP triester standards, samples were extracted by accelerated solvent extraction that completely separated OP diesters and triesters. OP diester fractions were cleaned up using weak anion exchange solid phase extraction and eluted with high ionic strength ammonium acetate buffer. Optimal analysis of chlorinated OP diesters was via decamethonium hydroxide dicationic reagent derivatization and by LC-ESI(+)–MS/MS, and for all non-chlorinated OP diesters by non-derivatized LC-ESI(−)–MS/MS. Except for derivatization LC-ESI(+)–MS/MS analysis of liver, at the 10 ng spiking level for the three matrices, recovery efficiencies, matrix effects and method limits of quantification (MLOQs) of OP diesters ranged from 55–116%, 92–119%, and 0.02–0.31 ng/g wet weight (ww) respectively. Plasma samples of n = 6 herring gulls (2010, Chantry Is., Laurentian Great Lakes) contained triphenyl phosphate and tris(1-3-dichloro-2-propyl) phosphate ranging from 1.3 to 4.0 ng/g ww and