Single step derivatization with CF3 enone of thiophene at ambient temperature to determine propellant grade hydrazines: a study by GC and GC-MS

Abstract

A simple, highly selective and rapid gas chromatography method (packed column with flame ionization detection) has been developed to determine hydrazine and monomethylhydrazine individually and for selective determination of hydrazine in the UH 25 mixture in organic medium. This method is based on the derivatization of hydrazine (at ambient temperature) with 1,1,1-trifluoro-4-(3-thienyl) (CF₃ enone) in the absence of catalyst/buffer which leads to the formation of corresponding pyrazolidine/pyrazoline/pyrazole. The organic derivatives thus formed are then detected and their presence is confirmed by GC-MS. The GC method provides good resolution between CF₃ enone and its derivatives with a total analysis time of 20 min. The concentration of CF₃ enone and derivatization time are optimized to determine hydrazines in the concentration range of 0.4 mM to 0.2 M. The calibration curves based on peak areas of CF₃ enone and its derivatives showed good linearity with r² ≈ 0.999 for the working range and the precision was found to be less than 1% for hydrazine, MMH and hydrazine in UH25. The recovery was found by the standard addition method. Under the established conditions, limits of detection were 20 μM for hydrazine, 10 μM for MMH and 20 μM for hydrazine in UH25. The tolerance limit for interfering amines was also found. The advantage of this method is the selective detection and determination of hydrazine in the UH25 mixture as 1,1-dimethylhydrazine present in UH25 cannot be derivatized with CF₃ enone.