Plasticizer Effects in the PVC Membrane of the Dibasic Phosphate Selective Electrode

Abstract

The PVC membrane of an ion-selective electrode (ISE) sensitive to dibasic phosphate ions (HPO4-ISE) has not been optimized for maximum selectivity, sensitivity, and useable ISE lifetime and further work was necessary to improve its performance. Two areas of investigation are reported here: include the parameters for the lipophilicity of the plasticizer compound used and the amount of cyclic polyamine ionophore incorporated in the PVC membrane. Six candidate plasticizers with a range of lipophilicity were evaluated for their effect on the useable lifetime, sensitivity, and selectivity of the ISE against 13 different anions. Selectivity was determined by a modified fixed interferent method, sensitivity was determined without interferents, and the usable lifetime evaluated at the elapsed time where 50% of the HPO4-ISE failed (L50). The results show that choosing a plasticizer that has a lipophilicity similar to the ionophore's results in the best selectivity and sensitivity and the longest L50.

Ambient Processed, Water-Stable, Aqueous-Gated sub 1 V n-type Carbon Nanotube Field Effect Transistor

“…The active channel of the CNTFET is covered with a tailor lipophilic membrane layer. This membrane layer contains 31.3% poly-vinyl chloride (PVC) which provides the structural support to the membrane 30 and 63.6% dioctyl sebacate (DOS) which acts as a plasticizer 31 . The lipophilic ion additives of this layer are 3% tetradodecylammonium tetrakis(4-chlorophenyl)borate (ETH 500) and 2.1% methyltridodecylammonium chloride (MDDA - Cl).…”

A rapid cadmium determination based on ion selective membrane potentiometric sensor by bis (salicylaldehydo)ethylenediimine as carrier

“…This divergence in electrode response in higher concentration of the ionophore caused the less selectivity and enhanced interference of the lipophilic counter ions of the test solution as assumed in the phase boundary potential model of carrier based ISEs. Plasticizer also plays an important role in electrode responses and influences the detection limits [19,20], the sensitivity and selectivity [21] of the electrodes. Moreover, the nature of the additive may have significant effect on the sensitivity and selectivity [22][23][24].…”

Plasticizer for Liquid Polymeric Membrane of Ion Selective Electrode Based on Thiazole Derivatives as Ionophore

“…2 shows a structure of thiazole-4-carboxamide (Th) that act as ionophore in this experiment. The ideal plasticizer should have the following properties: softens the PVC membrane, solubilizes the ionophore, insoluble in water, and is inert with respect to ion exchange [3]. The plasticizers must have plasticity or fluidity properties to be physically compatible with the polymer, so as to give a homogeneous organic phase [4].…”

“…These plasticizers must be fulfilled the four criteria such as high lipophilic, soluble with no crystallize formed, Noor Wahidah ZAINOL JAMIL et al, 2018 no exudation and give a better selective behavior of ISE [5]. The appropriate plasticizer to use in the sensor membrane specifies that the lipophilicity of the plasticizer should be as close as possible to that of the ionophore [3]. DOP is an ester of phthalic acid that appears as a light colored, odorless liquid and is used as a plasticizer for many resins and elastomers.…”

“…Although the rate ion exchange of plasticizer is small compared to the rate ion exchange of ionophore, the plasticizer is important in the membrane as it does not just soften the membrane but it also helps to increase the selectivity of ISE without interfering with ion exchange of ionophore. The plasticizer in the membrane also had a large effect on sensitivity, selectivity and useable service life [3]. The objective of this study is to select the best plasticizer from a various range of plasticizers (dioctyl phthalate (DOP), dibutyl phthalate (DBP), benzyl acetate (BA) and nitrobenzene (NB)) for ISE with thiazole-4-carboxamide (Th) as an ionophore using solution as analyte.…”