Phenytoin speciation with potentiometric and chronopotentiometric ion-selective membrane electrodes

S Jansod; M G Afshar; G A Crespo; Eric Bakker

doi:10.1016/j.bios.2015.12.011

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Phenytoin speciation with potentiometric and chronopotentiometric ion-selective membrane electrodes

Journal article

Peer reviewed

Phenytoin speciation with potentiometric and chronopotentiometric ion-selective membrane electrodes

S Jansod, M G Afshar, G A Crespo and Eric Bakker

Biosensors and Bioelectronics, Vol.79, pp.114-120

2016

DOI: https://doi.org/10.1016/j.bios.2015.12.011

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Abstract

Analytical Chemistry

Biomedical Engineering

Nanotechnology

chronopotentiometry

perm-selective membranes

phenytoin

potentiometry

speciation

We report on an electrochemical protocol based on perm-selective membranes to provide valuable information about the speciation of ionizable drugs, with phenytoin as a model example. Membranes containing varying amounts of tetradodecylammonium chloride (TDDA) were read out at zero current (potentiometry) and with applied current techniques (chronopotentiometry). Potentiometry allows one to assess the ionized form of phenytoin (pKa∼8.2) that corresponds to a negatively monocharged ion. A careful optimization of the membrane components resulted in a lower limit of detection (∼1.6μM) than previous reports. Once the pH (from 9 to 10) or the concentration of albumin is varied in the sample (from 0 to 30gL-1), the potentiometric signal changes abruptly as a result of reducing/increasing the ionized concentration of phenytoin. Therefore, potentiometry as a single technique is by itself not sufficient to obtain information about the concentration and speciation of the drug in the system. For this reason, a tandem configuration with chronopotentiometry as additional readout principle was used to determine the total and ionized concentration of phenytoin. In samples containing excess albumin the rate-limiting step for the chronopotentiometry readout appears to be the diffusion of ionized phenytoin preceded by comparatively rapid deprotonation and decomplexation reactions. This protocol was applied to measure phenytoin in pharmaceutical tables (100mg per tablet). This tandem approach can likely be extended to more ionizable drugs and may eventually be utilized in view of pharmacological monitoring of drugs during the delivery process. © 2015 Elsevier B.V.

Details

Title: Phenytoin speciation with potentiometric and chronopotentiometric ion-selective membrane electrodes
Authors: S Jansod (Author) - University of Geneva, Switzerland
M G Afshar (Author) - University of Geneva, Switzerland
G A Crespo (Author) - University of Geneva, Switzerland
Eric Bakker (Author) - University of Geneva, Switzerland
Publication details: Biosensors and Bioelectronics, Vol.79, pp.114-120
Publisher: Elsevier BV
Date published: 2016
DOI: 10.1016/j.bios.2015.12.011
ISSN: 0956-5663
Organisation Unit: University of the Sunshine Coast, Queensland
Language: English
Record Identifier: 99449582802621
Output Type: Journal article

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Web Of Science research areas: Biophysics; Biotechnology & Applied Microbiology; Chemistry, Analytical; Electrochemistry; Nanoscience & Nanotechnology