Determination of Hydrazine and Its Derivatives

The reaction is achieved in hydrogen carbonate buffer. It is a back titration. The excess iodine is titrated with thiosulfate. Phenylhydrazine, semicarbazide, and thiosemicarbazide are determined according to the same principle  

Some organic arsenicals, where arsenic exhibits the +ni oxidation state, can be titrated directly with an iodine solution. They are methylarsine CH3ASH2, methyldiiodoarsine CH3ASI2, and methylarsine oxide CH3ASO  

Methylarsinic acid is formed. In methylarsine and methyldiiodoarsine, arsenic is at oxidation state +III, and both hydrogen atoms and both iodine atoms bound to arsenic atom must be considered at oxidation state —I. Some other organic arsenicals must be mineralized before their arsenic content can be determined (see Sect. 18.10.7). 

Antimony +III in the antimonyl cation SbO+ belongs to the redox couple Sb20s/Sb0+ and obeys the half-redox equilibrium 

The reaction of the oxidation of Sb -I-III with iodine in acidic medium is 

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Titrimetric proceedures for the determination of KjEefCN) in alkaline media, also using hydrazine sulphate, have been desaibed. Determination of hydrazine and its derivatives is also important. A back-titration technique involving iodine monochloride in 5M-HC1 as the oxidant is simpler and of wider applicability than previous methods. ... 

It is therefore clear that reliable and sensitive analytical methods are needed for the determination of hydrazine and its derivatives. Techniques have been developed for hydrazine measurements based on spectrophotometry [5], fluorimetry [6], chemiluminescence [7], and chromatography [8]. However, drawbacks of these procedures include diflhcult sample preparation, the need for derivatization, and insufficient sensitivity, which limit their utility. In contrast, electrochemical methods generally present the advantages of simplicity and high sensitivity. 

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