Development of a dispersive liquid–liquid microextraction method for organophosphorus flame retardants and plastizicers determination in water samples

A fast, inexpensive and efficient sample preparation method for the determination of 10 organophosphorus compounds in water samples is presented. Analytes were extracted using the dispersive liquid–liquid microextraction (DLLME) technique and determined by gas chromatography with nitrogen–phosphorus detection (GC-NPD). The influence of several variables (e.g. type and volume of dispersant and extraction solvents, ionic strength, shaking time and mode, etc.) on the performance of the sample preparation step was carefully evaluated. Under final working conditions, 1 mL of acetone containing a 2% of 1,1,1-trichloroethane (20 μL) was added to 10 mL of water with 20% of sodium chloride. The ternary mixture was centrifuged at 3500 rpm to allow phase separation. After removing the aqueous supernatant, an aliquot of the settled extract was injected in the GC-NPD system. Under the above conditions, the method provided enrichment factors between 190 and 830 times (depending on the considered compound), relative standard deviations below 10%, except for tris(2-ethylhexyl) phosphate (TEHP), and quantification limits between 0.01 and 0.08 ng/mL. Matrix effects were assessed using different water samples, and accuracy was evaluated by comparison with solid-phase microextraction.