Photochemically induced fluorescence studies of 1,3-diethyl-1,3-diphenylurea as stabilizer and its quantitative determination.

The photochemically induced fluorescence (PIF) studies of 1,3-diethyl-1,3-diphenylurea or ethyl centralite (EC) as stabilizer have been carried out under various conditions. Influences of solvent type (water, methanol, acetonitrile and chloroform), oxygen dependence and UV irradiation time on the spectroscopic properties of EC were studied. In order to obtain a better understanding of the photochemical mechanism, products were identified by mass spectrometry study. A novel fluorimetric method has been developed for the determination of EC based on the PIF. The method is based on the use of UV irradiation to produce fluorescent derivatives from EC as a non-fluorescent molecule. The determination is carried out by UV irradiation for 4min through measuring the fluorescence intensity in 354nm when an excitation wavelength of 227nm was used. Parameters related to the analytical signal and to the PIF are optimized. The linear range for determination of EC was 4×10(-8) to 2×10(-6)mol L(-1) and the limit of detection (LOD) was 2×10(-8)mol L(-1) with relative standard deviation (R.S.D.) of 3% (n=5). Finally, the proposed method was successfully applied for the determination of EC in real propellant samples and the acquired results were favorably compared to those obtained with HPLC method.