Improved and Novel Methods for Investigating Organophosphate Esters in Particulate Matter

A pressurized liquid extraction (PLE) method for the extraction of 31 organophosphate esters (OPEs) and novel organophosphate esters (NOPEs) has been developed. Unlike previously published methods, this method utilizes the high-throughput nature of PLE (as opposed to Soxhlet or sonication methods) without using potentially harmful organic solvents like methylene chloride. Combinations of hexane and acetone and hexane and ethyl acetate at various temperatures were examined. Extracts were concentrated and analyzed via gas chromatography-mass spectrometry. The final optimized method utilized 1:1 <i>v</i>/<i>v</i> hexane/ethyl acetate at 100 °C for three static cycles (5 min each) at 80% flush volume and a 100 s N₂ purge. This provided average surrogate corrected target analyte percent recoveries in spike and recovery experiments (<i>n</i> = 6) for OPEs and NOPEs of 106 ± 13%, with average surrogate recoveries of 88.6 ± 7.3%. The developed method was further validated using standard reference materials and was then applied to atmospheric particulate matter samples collected in the city of Providence, RI. The dataset reflected ambient concentrations of 16 OPEs and NOPEs (reported in pg m^-3) for the first time in the greater Providence metropolitan area, including one of the first reports of NOPEs in atmospheric particulate matter in the U.S.