Analysis of Hydrazines

Hydrazines are used in a variety of industrial applications. Both hydrazine and unsymmetrical dimethylhydrazine (1,1-dimethylhydrazine, UDMH) are used as rocket fuels because their combustion is highly exothermic. Hydrazine is also used as a corrosion inhibitor in boilers. Other derivatives of hydrazine are used in dyes, explosives, and pesticides.

Analysis of Hydrazines

Hydrazine and methylhydrazines can be determined by either gas chromatography (GC), liquid chromatography (HPLC), or ion chromatography (IC). Liquid or ion chromatography have limited resolving capability, and literature reports show that UDMH and SDMH are not resolved. The pros and cons of various methods are discussed below.

Hydrazines by GC

GC on the other hand resolves each compound very nicely. The chromatogram below showing a mixed hydrazine standard at approximately 5 ug/mL was obtained on a 30 m X 0.53 mm RTX-35 (Restek) at 40^oC and a nitrogen specific (TSD) detector.

Hydrazines are easily extracted with acetone, and the primary amine

functions derivatized as dimethylhydrazone groups. Hydrazine is derivatized during extraction to acetone azine. Derivatization produces compounds which are more amenable to GC. SDMH remains unreacted. The asymmetric peak shape for SDMH in the chromatogram is a result of the very polar, underivatized SDMH. Aqueous samples can be analyzed for ppm levels, while soils can be extracted, concentrated, and analyzed for ppb levels. For a quotation...

Hydrazine by HPLC

While GC has detection limits for hydrazine in water in the ppm range, derivatization coupled with HPLC with uv detection has a detection limit of ~4 ug/L in water.

Hydrazine is derivatized with 4-hydroxybenzaldehyde to form a hydrazone which is then analyzed by reverse phase HPLC according to H. Kirchherr, J. Chrom. 1993 (617), 157-162.

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Hydrazine by HPLC

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