Electrochemical characterisation and sensing of diclofenac anion and dibucaine cation by ion transfer across water and dichlorohexane interface
Ion sensing is a significant challenge in both clinical diagnosis and environmental monitoring. Ion transfer reactions at liquid | liquid interfaces allow detection of substances that are not easy to oxidise/reduce or that undergo significant interference in these reactions. In addition, it offer...
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| Main Author: | |
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| Format: | Thesis |
| Language: | English |
| Published: |
2021
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| Subjects: | |
| Online Access: | http://psasir.upm.edu.my/id/eprint/104172/1/FS%202022%2029%20IR.pdf |
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| Summary: | Ion sensing is a significant challenge in both clinical diagnosis and
environmental monitoring. Ion transfer reactions at liquid | liquid interfaces
allow detection of substances that are not easy to oxidise/reduce or that
undergo significant interference in these reactions. In addition, it offers the
advantages of simplicity of instrumentation, easily of miniaturisation and
portability. However, very few sensing applications have been reported for the
quantitative analysis of organic molecules, including drugs. This study
discussed the characterisation, and application of ion transfer at the interface
between two immiscible electrolyte solutions (ITIES) using cyclic voltammetry
(CV) and differential pulse voltammetry (DPV). Early studies have relied on the
exploration of the electrochemical behaviour of diclofenac anion (DCF-) and
dibucaine cation (DIC+) via water|1,6-dichlorohexane (1,6-DCH) at such regular
ITIES and in particular examination of the pH of the aqueous phase. Both ions
were found to undergo ion-transfer voltammetry at the liquid | liquid interface.
Some of the analytical parameters, such as standard transfer potential, the
Gibbs energy of transfer and the partition coefficient, for DCF- and DIC+ were
determined. Subsequently, essential modifications to the ITIES by micropores
silicon nitride membrane were brought to enhance the analytical performance
and lower the detection limits. The micro-ITIES array formed with 2500
micropores arranged in a cubic close-packed (CCP) arrangement, with a
diameter of 2.5±0.09 μm, a pore centre-to-centre separation of 12.65±0.13 μm
and 100 nm membrane thickness, was electrochemically characterised by ion
transfer of the model analyte, tetramethylammonium cation (TMA+), across the
water | 1,6-DCH interface. The resulting voltammogram has showed the linear
diffusion dominance within the arrays, suppressing the radial diffusion at the
edge of the arrays, due to overlapping diffusion profiles at adjacent micro-ITIES
resulted in lower experimental current. The analytical performance of micro-
ITIES to drug molecules (DCF- and DIC+) detection in the aqueous phase was
investigated, with the limits of detection (LODs) in the ranges of 8–56 μM and 4–24 μM were calculated to be 1.5±0.05 μM and 0.9±0.06 μM for DCF- and
DIC+, respectively. In addition, the influence of possible interfering substances
(ascorbic acid, sugar, amino acid, urea, and metal ions) on the detection of
DCF- and DIC+ was investigated. Finally, the ability to use electrochemistry at
liquid | liquid micro-interface for direct determination of the targeted drugs in
bio-mimic fluids (serum and saliva) and in a realistic mixture (human urine)
were assessed. Both drugs could be detected in biological matrices, despite of
deproteinisation of samples is required for detecting DCF in artificial serum.
The LODs were 12.9±.5 μM and 1.4±0.02 μM in artificial serum, 1.8±0.2 μM
and 1.5±0.14 μM in artificial saliva and 2.6±0.2 μM and 1.2±0.12 μM in human
urine sample for DCF- and DIC+, respectively. |
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