FLUORESCENT DETECTION OF HYDRAZINE, MONOMETHYLHYDRAZINE, AND 1,1-DIMETHYLHYDRAZINE BY DERIVATIZATION WITH AROMATIC DICARBALDEHYDES

A chemical derivatization scheme has been developed for the sensitive and selective determination of hydrazine, monomethylhydrazine (MMH) an d 1,1-dimethylhydrazine (UDMH) by fluorescence spectrometry. Incorpora tion of hydrazine into an aromatic framework by derivatization with o- phthalaldehyde (OPA), naphthalene-2,3-dicarbaldehyde (NDA), or anthrac ene-2,3-dicarbaldehyde (ADA) creates an efficient fluorophore the emis sion wavelength of which is red-shifted from the original reagent. The fluorescence emission for each of the different derivatizing reagents (OPA, NDA, and ADA), is minimal and nearly within the noise of the ba ckground. The hydrazine derivatives, on the other hand, are intensely fluorescent and characterized by a broad fluorescence emission centred at 376 nm for OPA, 500 nm for NDA, and 549 mm for ADA. For the NDA hy drazine derivative, a linear concentration dependence is observed from 50 ng l(-1) to 500 mu g l(-1) of hydrazine (correlation coefficient, r > 0.999). The response time necessary to give 90% of a full-scale re sponse is <2 min. The response of the ADA reagent is similar; however, its response time is faster (<0.5 min), and its detection limit is hi gher (150 ng l(-1)). By careful control of the pH and the aromatic dic arbaldehyde chosen, it is possible to differentiate quantitatively bet ween the hydrazine, MMH, and UDMH levels present in mixed samples. The detection limits for MMH and UDMH using the NDA reagent are 120 ng l( -1) and 40 mu g l(-1), respectively.