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Ion-pairing agents in ion-selective electrodes for diquat, paraquat and 4,4-dipyridinium dications

Biomedical Sciences Research Institute Computer Science Research Institute Environmental Sciences Research Institute Nanotechnology & Advanced Materials Research Institute

Marnoch, Gordon, Owusu, RK and Thomas, JDR (1987) Ion-pairing agents in ion-selective electrodes for diquat, paraquat and 4,4-dipyridinium dications. The Analyst, 112 (10). pp. 1347-1353. [Journal article]

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URL: http://dx.doi.org/10.1039/AN9871201347

DOI: doi:10.1039/AN9871201347

Abstract

Phosphorus hexafluoride (PF6), anthraquinone-2-sulphonate (AS), octylsulphate (OS), picrate (PIC), dipicrylaminate (DPA), Diamine Green B (DGB), tetraphenylborate (TPB) and tetrakis-4-chlorophenylborate (T4CIPB) have been studied as possible ion-pairing agents for use in PVC-type liquid membrane ion-selective electrodes (ISEs) for diquat (DQT), paraquat (PQT) and 4,4′-dipyridinium (4,4′-DPy). Of these, only PF6, PIC, DGB, TPB and T4CIPB formed precipitates with DQT, PQT and 4,4′-DPy in aqueous solution, and only PF6, TPB and T4CIPB gave good electrodes; PF6-based electrodes were not selective.The analogy between ISE function and ion-pair extraction into an organic phase system is explored in detail. ISE characteristics, e.g., selectivity and minimum detectable activity of sample ion [a(min)] are quantitatively related to the sample ion membrane site association equilibrium and the lipophilicity of the ion pair formed.In agreement with the proposed theory, PIC is not sufficiently lipophilic to form the basis of a functional ISE for DQT, PQT or 4,4′-DPy. ISEs with T4CIPB as the membrane site show the best sensitivity for DQT (3 × 10–8M) or PQT (2 × 10–7M). The experimental selectivity coefficients for these ISEs in both instances are shown to be near to those calculated. Electrodes for 4,4′-DPy, studied as model systems, show an anomalously poor selectivity or sensitivity.

Item Type:Journal article
Faculties and Schools:Faculty of Life and Health Sciences
Faculty of Life and Health Sciences > School of Biomedical Sciences
Research Institutes and Groups:Biomedical Sciences Research Institute
Biomedical Sciences Research Institute > Northern Ireland Centre for Food and Health (NICHE)
ID Code:17395
Deposited By:Dr Richard Owusu-Apenten
Deposited On:03 Mar 2011 14:04
Last Modified:28 Jan 2014 14:47

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