Quantitative determination of tris-(2,3-dibromopropyl) phosphate by densitometry of thin layer chromatograms

The flame retardant tris-(2,3-dibromopropyl) phosphate (Tris) was chromatographed on silica gel thin layer plates, using ethyl acetate-hexane (30+70) as the developing solvent. Tris was visualized by spraying the chromatogram with 1% aqueous silver nitrate followed by exposure to ultraviolet light for 40 min. Tris appeared as dark gray spots on a white background; the spots were quantitated by densitometry at 660 nm. The lower level of sensitivity was 50 ng; calibration plots were linear from 50 to 800 ng. The procedure was developed to determine the levels of unmetabolized Tris remaining after exposure to sewage sludge suspensions. Recovery of Tris from 3 sewage sludge samples fortified at the 1.0 ppm level averaged 97%.