Determination of phosphate esters in formulated products

If no other phosphate is present, determine the total phosphate content of both product and raw material. 

If no other salt of a weak acid is present, determine the monoester content of both product and raw material by cation exchange and potentiometric titration. If no weak base is present, the cation exchange can be omitted. 

Determine the triester content, if any, of both product and raw material. The triester is isolated in the nonionic fraction. If other nonionic matter is present, determine the triester from its total phosphate content. This is likely to be less useful for monoesters than for diesters. 

Analyse by NMR. This is the simplest and best approach, but the apparatus is expensive. 

ASTM Method D 4251-89 Standard Test Method for Active Matter in Anionic Surfactants by Potentiometric Titration. American Society for Testing and Materials, Philadelphia, USA. 

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