Analysis of cationics and amphoterics

As in previous chapters, this chapter deals with the analysis of cationics and amphoterics either alone, as raw materials or as fractions isolated by ion exchange or otherwise, or in formulated products. Fractions isolated by ion exchange are likely to contain other materials, analogously with anionics. Amines, ethoxylated amines and amine oxides are included in this chapter because they are bases and capable of a cationic function. They are retained as cations by ion-exchange columns and do not appear in the nonionic fraction of separated mixtures, they can be titrated with acids and, in acid solution, with sodium dodecyl sulphate, provided the ethylene oxide chains of ethoxylates are not too long. 

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Takano S, Tsuji K (1983) Analysis of cationic and amphoteric surfactants. III. Structural analysis of imidazolinium cationic surfactants. J Am Oil Chem Soc 60 870... 

Mass sjrectrometry is not routinely applied to analysis of cationic and amphoteric surfactants. The most common cationic surfactants, the quaternary amine salts, cannot be analyzed directly by conventional GC-MS or by direct electron impact MS because of their low volatility. Under El or Cl conditions, quaternary amines normally decompose to tertiary amines, which can become ionized or protonated for MS detection. Thus, ordinary MS shows only fragments and rearrangement products, and its use is quite limited in the analysis of materials of unknown composition. 

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