engleski

Investigation of the homologs of tallow fatty alcohol and oleyl alcohol ethoxylates using high sensitive potentiometric sensor for non-ionic surfactants

Tallow fatty alcohol and oleyl alcohol ethoxylates are groups of commercialy interesting polyethoxylated non-ionic surfactants (EONS) widely represented in detergents, household cleaning and personal care products. For the investigation of mentioned groups of EONS, in a recent work we optimised and characterised PVC liquid membrane surfactant sensitive electrode, with the aim to obtain stable, reproducible and long lived device applicable for the end-point detection in potentiometric titrations of EONS in reaction based on the formation of tetraphenylborate (TPB) salts of pseudocationic complexes of EONS with barium cation. Membrane incorporates the 1, 3-didecyl-2-methylimidazolium-tetraphenylborate (DMI-TPB) as the electroactive recognition element, previously developed in our laboratories and succesfuly employed in potentiometric titrations of ionic surfactants, and bis(2-ethylhexyl) phthalate (DEHP) as plasticizer. This study included characterisation of the sensor: response characteristics and dynamic response of the sensor, with special emphasis on Ba-ethoxylates of EONS investigated. Because of non-stoichiometric reaction of EONS and barium ion we designed a special testing procedure with which we investigated dynamic responses of the electrode on Ba-ethoxylates of EONS homologs investigated, Triton X-100 and Brij 35 as representatives of analytical grade EONS and two polyethylene glycols (PEG 600 and PEG 1000). Stoichiometry of barium ethoxylates for the investigated EONS was examined with well known titration procedure, using here presented self-designed potentiometric sensor as end-point indicator. Sensor is usable in real solutions with high accuracy and precision, with some exceptions for low ethoxylated EONS, and presense of strong interferents, for example high concentration of anionic surfactants.

Non-ionic surfactants; ethoxylates; potentiometric sensor

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