Determination of short-chain sulphonates

It is sometimes necessary to determine sodium (or potassium) toluene, xylene or cumene sulphonate present as a hydrotrope in products containing alkylbenzene sulphonates. This can be done by removing the alkylbenzene sulphonate and determining the short-chain sulphonate by ultraviolet spectroscopy. BS 3762, Part 3.10 [12], describes a method for toluene and xylene sulphonates. A similar method can also be used for cumene sulphonate. 

Extract the alkylbenzene sulphonic acid as described in section 5.2.4. The aqueous extracts contain the short-chain sulphonate. 

Combine all the aqueous extracts and washes and evaporate to dryness. 

Dissolve the residue in water and neutralise to pH 4.5 with 2.5 M sodium hydroxide. 

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