Cationic detergents surfactants after ion exchange

In the determination of nonionic surfactants according to the method described above (. 1.7.3), cationic surfactants are also detected. The 

Determination of the nonionic surfactants passing through the cation exchanger is performed exactly as described in Method 4.1.7.3. 

If there are reproducible differences between the results of determination of the nonionic surfactants without cation exchange in comparison with those subjected to cation exchange, this means the water under analysis 

Direct determination of the cationic surfactants (detergents) is advisable only if considerable differences arise in the determination of nonionic surfactants (detergents) with and without ion exchange. The method using bromophenol blue may be employed as a more semi-quantitative determination of cationic surfactants (detergents) in water. 

Cetyltrimethylammonium bromide (CTAB, molecular weight 36. 3) may be used as a cationic calibration surfactant. Dissolve 1 g of this substance 

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