Determination of 1,1-dimethylhydrazine (UDMH) in water by HPLC-UV using micellar catalysis for preparation of the derivatives

Abstract

The possibility of improving the HPLC-UV determination of 1, 1-dimethylhydrazine (unsymmetrical dimethylhydrazine, UDMH) with preliminary derivatization with 2-nitrobenzaldehyde (2NBA) and 4-nitrobenzaldehyde (4NBA) in an aqueous medium when using micellar catalysis of the reaction to obtain the derivatives is studied. Conditions of UDMH derivatization (pH, concentrations of the reagent and surfactant (SAS), temperature and reaction time) were optimized. It is shown that complete derivatization occurs at room temperature during 45 and 30 min (for 2NBA and 4NBA, respectively) at pH 9 in the presence of 87 mM sodium dodecyl sulfate (SDS) and the excess content of the reagents. Ion chromatography was used to prove the quantitative yields under conditions of derivatization by the absence of UDMH in the reaction mixture. Micellar catalysis provides the completeness of derivatization carried out under milder conditions and in the region of low UDMH concentrations thus expanding the linear range of UDMH determination in water. ZORBAX Eclipse Plus C18 column (150 × 3.0 mm, 3.5 μ m) was used for separation of the components. A mixture of acetonitrile and 10 mM ammonia buffer solution pH 7 (50/50 vol.%) at a flow rate of 0.7 ml/min in isocratic mode was used as a mobile phase. Detection of dimethylhydrazines (2NBA and 4NBA) was performed at 308 and 394 nm, respectively. The obtained detection limits of UDMH ( S / N = 3) were 3 and 1.5 μ g/L for 2NBA and 4NBA, respectively. Duration of chromatographic analysis was 15 min. The developed technique of water analysis provides simple, sensitive and reproducible HPLC-UV determination of UDMH in a concentration range of 5 – 1000 μ g/L without additional preconcentration.