The Influence of Plasticizers on the Response Characteristics of the Surfactant Sensor for Cationic Surfactant Determination in Disinfectants and Antiseptics

Abstract

Surfactant liquid-membrane type sensors are usually made of a PVC, ionophore and a plasticizer. Plasticizers soften the PVC. Due to their lipophilicity, they influence the ion exchange across the membrane, ionophore solubility, membrane resistance and, consequently, the analytical signal. We used the DMI-TPB as an ionophore, six different plasticizers [2-nitrophenyl-octyl-ether (P1), bis(2-ethylhexyl) phthalate (P2), bis(2-ethylhexyl) sebacate (P3), 2-nitrophenyl phenyl ether (P4), dibutyl phthalate (P5) and dibutyl sebacate (P6)] and a PVC to produce ionic surfactant sensors. Sensor formulation with P1 showed the best potentiometric response to four usually used cationic surfactant, with the lowest LOD, 7 × 10−7 M; and potentiometric titration curves with well-defined and sharp inflexion points. The sensor with P6 showed the lowest analytical performances. Surfactant sensor with P1 was selected for quantification of cationic surfactant in model solutions and commercial samples of disinfectants and antiseptics. It showed high accuracy and precision in all determinations, with recovery from 98.2 to 99.6, and good agreement with the results obtained with surfactant sensor used as a referent one, and a standard two-phase titration method. RDS values were lower than 0.5% for all determinations.

Potentiometric Surfactant Sensor for Anionic Surfactants Based on 1,3-dioctadecyl-1H-imidazol-3-ium tetraphenylborate

“…There are mainly two types of surfactant sensors: solid-state surfactant sensors [16,17] and PVC-based liquid membrane-type surfactant sensors [18]. Membranes based on PVC consist of a high molecular weight PVC and a plasticizer in a 2:1 weight ratio, and usually a 1% ionophore, which is an active substance of the sensing membrane [19]. The plasticizer softens the PVC and serves as a solvent for the highly lipophilic ionophore.…”

Titrimetric methods for determining cationic surfactants

“…This eliminates the need to manufacture a special liquid membrane or other electrodes, which were most often used until now for the potentiometric titration of surface-active substances. The reverse titration of CS with the standard solution of sodium dodecyl sulfate is usually performed [63]. It is important to note that when the concentration of CS is very low, its adsorption by glassware is significant.…”

The 1,3-Dioctadecyl-1H-imidazol-3-ium Based Potentiometric Surfactant Sensor for Detecting Cationic Surfactants in Commercial Products

“…The employment of potentiometric chemical sensors [ 8 ] for the quantitative analysis of cationic surfactants represents a valuable substitution for existing methods. These devices can be divided into solid-state [ 9 ] and liquid membrane-type potentiometric sensors [ 10 , 11 ], which contain an ion-pair (ionophore) sensing element in the PVC-based liquid membranes. The ionophore is incorporated into the sensing membrane together with a plasticizer and a PVC [ 12 , 13 , 14 ].…”

“…The ideal ionophore should have low solubility in water (inorganic solvent) and high solubility in the sensor membrane, which acts as an organic solvent (for the ionophore), as well as high stability. Suitable plasticizer selection has a crucial role in improving the sensor response and stability [ 10 , 11 ]. The addition of carbon-based nanomaterials to the sensing membrane can also improve the response properties [ 17 , 18 ].…”