Organophosphate esters by GC-MS: An optimized method for aquatic risk assessment

Organophosphate esters used as flame retardants and plasticizers are ubiquitous contaminants in surface waters. Many studies indicate that these compounds are neurotoxicants, endocrine disruptors, and may affect reproduction and development of aquatic organisms. Thus, analytical methods that allow accurate quantification of these contaminants at environmentally relevant concentrations are desirable for risk assessment studies. In this study, a method based on solid phase extraction and gas chromatography coupled to mass spectrometry was developed for determination of organophosphate esters in river water extracts. Multivariate optimization was used to determine the best conditions for injection of larger volumes of sample in a Programmable Temperature Vaporization inlet. Furthermore, the matrix effect on the instrumental response was evaluated and compensated by association of extraction-blank-matched calibration and isotopically labeled focus standards. The method quantification limits ranged from 0.009 to 0.11 µg/L, staying below the predicted non-effect concentration for the aquatic compartment for all analytes, which is a requisite for using in risk assessment studies. The method was applied to freshwater samples collected in rivers from the Sao Paulo State, Brazil, and eight out of the ten target organophosphate esters were quantified, being tris(2-chloroisopropyl) phosphate and tris(phenyl) phosphate the most frequently detected compounds.