The Solution-polymer Interface: PVC ISE-s and MIP-s

George Horvai 1Timea Pap 2

1. Budapest University of Technology and Economics, Dept. Chem. Inf. Techn., Gellert ter, Budapest H-1111, Hungary
2. Hung. Acad. Sci., Techn. Anal. Res. Group, Gellert ter 4, Budapest H-1111, Hungary

Abstract



Polymer-liquid interfaces constitute the sensing area of several sensors. Adsorption at this interface contributes to sensing the analyte and to various types of interferences. In this lecture we show results concerning the structure of two interesting systems:
1. Ion-selective membranes made from plasticized PVC and used in aqueous solutions
2. Molecularly imprinted polymers used in different solvents

Most commercial ion-selective sensors for clinical analysis are made with plasticized PVC membranes. The structure of plasticized PVC is not well understood and the compositional changes in the immediate vicinity of the surface were completely unknown. We have shown by various spectroscopies that concentration gradients of different components penetrate at different depths into the membrane. Interestingly the surface-near region was found to be almost pure liquid plasticizer without much polymer. This result has been used recently by others for different purposes. Plasticized polyurethane sensor membranes were found to behave in the same way and this is important for biocompatibility. Fundamental electrochemical studies to determine ion transfer rates at ITIES could be carried out using the plasticized PVC interface.

Molecular imprinting is an attractive way to create very selective adsorbents. These can be used for example in QCMB sensors. The response and particularly the selectivity of such sensors depends crucially on the adsorption isotherms of individual substances and mixtures. We could recently show that simultaneous adsorption of two substances may not only lead to competition but also to synergy. Selectivity studies have also helped to understand how individual molecules are adsorbed and what can be the structure of the binding sites.

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Presentation: Tutorial lecture at SMCBS 2003 Workshop, by George Horvai
See On-line Journal of SMCBS 2003 Workshop

Submitted: 2003-09-16 19:41
Revised:   2009-06-08 12:55
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