Determination of Hydrazine and 1,1 -Dimethylhydrazine as Salicyldehyde Derivates by Liquid Chromatography With Electrochemical Detection P. E. Kester 1) / N. D. Danielson* Department of Chemistry, Miami University, Oxford, OH 45056, USA Key Words Liquid chromatography Electrochemical detection Hydrazine derivatives Derivatization with salicylaldehyde Summary Determination of hydrazine and 1,1-dimethylhydrazine after derivatization with salicylaldehyde was done using high-performance liquid chromatography with electro- chemical detection. The oxidation of the phenolic group of salicylaldazine (S-HY) and salicylaldehyde-l,l-dime- thylhydrazone (S-UDMH) was optimized with respect to ionic strength, pH, and applied potential. Less than 5 ng of S-HY and S-UDMH could be detected. The detection limits for hydrazine and 1,1 -dimethylhydrazine solutions were estimated to be 0.025 and 0.20 ppm, respectively. Introduction Hydrazine is widely used as a synthetic reagent, blowing agent, rocket fuel, and oxygen scavenger in boiler feedwater systems [1]. Considerable interest has been taken in the quantitative determination of hydrazine and its methyl derivatives due to their toxicity and suspected carcinogenic characteristics [2]. Hydrazine, monomethylhydrazine, and 1,1-dimethylhydra- zinc have been determined by a variety of methods. Oxidative or acid-base titrations [3] tend to lack selectivity for a particular hydrazine compound and are generally not sui- table for trace amounts. The colorimetric method of Pezes and Petit [4] is well accepted for hydrazine but cannot be used for other hydrazino compounds. Selectivity in deter- mination of hydrazines was added by gas chromatography analysis; however, in general only percentage levels from 1) Present Address: Champion International Corp., Knightsbridge, Hamilton, Ohio 45020 (USA) 2-30 were determined [5, 6]. In addition, these methods are plagued by heavy liquid phase coatings and subsequent peak tailing [5, 6], short column lifetimes [7], and indirect methods of calculating percent hydrazine [8]. High-performance liquid chromatography (HPLC) has been used successfully in both separation and quantitation of hydrazine and methyl hydrazines. A direct method was pro- posed by Fiala and Kulakis [9] using a cation-exchange sep- aration at pH 8.9 followed by electrochemical oxidation at + 1.00 V vs. Ag/AgCI. Since hydrazine compounds such as hydralazine can undergo facile air oxidation in basic solu- tions, sample integrity might be in question particularily if long sample storage before analysis was unavoidable. Very recently, the reversed-phase separation of hydrazines by HPLC with electrochemical detection was reported [10]. Application of quite low oxidation potentials was possible due to electrochemical pretreatment of the glassy carbon electrode. The lack of hydrophobic character of the hydra- zino compounds caused retention times to be less than 5 minutes even with use of a completely aqueous mobile phase. The possibility of sample matrix interference with the separation seems quite likely. Abdou, Medwick and Bailey [ 11 ] proposed the derivatization reactions of hydrazine (HY) and 1,1-dimethylhydrazine (UDMH) with salicylaldehyde to be used prior to separation by reversed-phase HPLC and UV detection. 0% / H H H2NNH2 "4- 2 OH ) -P 2 H20 OH HO HY Salicylaldazine (S-HY) ,/H H 3C.~ H3c/N-NH2 Jr" H UDMH H3C /H ) H3c/N --NHo~_~ ~ H20 Salicylaldehyde-l,1- dimethylhydrazone (S-UDMH) ChromatographiaVol. 18, No. 3, M~irz 1984 Originals 125 0009-5893/84/3 0125--04 $ 03.00/0 1984 Friedr. Vieweg & Sohn Verlagsgesellschaft mbH