A clear,amine-containing poly(vinyl chloride) membrane for in situ optical detection of 2,4,6-trinitrotoluene

A membrane has been developed for the direct determination of 2,4,6-trinitrotoluene (TNT) in natural waters at levels as low as 10 ng ml^?1. A typical membrane is prepared by dissolving the following in tetrahydrofuran: 0.5 g of poly(vinyl chloride) (PVC), 0.2 ml of dioctyl phthalate to serve as a plasticizer and 0.12 ml of Jeffamine T403, a polyoxyethyleneamine which reacts with TNT to produce a colored product. The membrane is formed by casting the solution into a glass Petri dish with a diameter of 8 cm and allowing the solvent to evaporate slowly. Trace amounts of 1,3,5-trinitrobenzene (TNB), 2,4,5-trinitrotoluene (2,4,5-TNT) and N-picryl-N-methylnitramine (tetryl) also react with the membrane to produce a reddish brown color, but their visible absorption spectra differ from that of TNT. The membranes remain clear indefinitely in water. After storage for 80 days in air in a sealed container, over 80% of the amine remains in the membranes. After exposure to water for 10 days, over 40% of the amine remains in the membranes, which continue to respond to TNT. The membrane can be used to determine TNT in untreated water samples of pH 6–9. Recoveries of 0.1–4.0 mg l^?1 of TNT from spiked groundwater ranged from 95 to 105%. Results by direct analysis of turbid water samples agreed with those obtained by high-performance liquid chromatography.