PVC membrane electrode has ionophore/plasticiser membrane composition optimised for the determination of ionic surfactants
The Metrohm High Sense Surfactant Electrode renders two-phase titration obsolete - no more need for toxic chloroform. Surfactant analysis is extremely important the world over. Surfactants are crucial constituents, particularly in cosmetics, detergents, cleansers and pharmaceuticals.
Whether in formulations or starting materials - the content should be determined as quickly, precisely and accurately as possible.
The hitherto usual two-phase titration employs chloroform, a solvent nowadays frowned upon.
Further, in several cases the titration endpoint can be detected only with difficulty and the titration cannot be automated.
The Metrohm High Sense Surfactant Electrode is a PVC membrane electrode whose membrane composition (ionophore/plasticiser) has been especially optimised for the determination of ionic surfactants.
The potential is formed by a specific interaction between the ion carrier incorporated in the PVC membrane and the analyte ions (surfactants) in the sample solution.
This interaction produces an electrical potential difference at the phase boundary sample solution/membrane that can be measured against a reference electrode.
The High Sense Surfactant Electrode has a working life of about one year or around 10,000 titrations, but should not come into contact with organic solvents such as acetone, tetrahydrofuran and chloroform. The Titroprocessors or Titrinos are suitable for use as a titrator.
The choice of titrant is very important.
The lower the solubility of the compounds formed, ie, the longer the chains, the steeper and more pronounced the potential jumps.
The titrants are preferably used as 0.004mol/l solutions.
For anionic surfactants, the Tego trant A 100 titrant, available from Metrohm, has proved outstanding, whereas for cationic surfactants sodium dodecylsulphate (Merck 12533 or Fluka 71727) is normally used.
A large number of practical titrations have been performed in the Metrohm application laboratory.
These are described in Application Bulletin No 233 available free from Metrohm UK.
