3 research outputs found
Capacitive Model for Coulometric Readout of Ion-Selective Electrodes
We
present here a capacitive model for the coulometric signal transduction
readout of solid-contact ion-selective membrane electrodes (SC-ISE)
with a conducting polymer (CP) as an intermediate layer for the detection
of anions. The capacitive model correlates well with experimental
data obtained for chloride-selective SC-ISEs utilizing polyÂ(3,4-ethylenedioxythiophene)
(PEDOT) doped with chloride as the ion-to-electron transducer. Additionally,
Prussian blue is used as a simple sodium capacitor to further demonstrate
the role of the transduction layer. The influence of different thicknesses
of PEDOT as a conducting polymer transducer, different thicknesses
of the overlaying ion-selective membranes deposited by drop casting
and spin coating, and different compositions of the chloride-selective
membrane are explored. The responses are evaluated in terms of currentâtime,
chargeâtime, and chargeâchloride activity relationships.
The utility of the sensor with coulometric readout is illustrated
by the monitoring of very small concentration changes in solution
Solid-Contact Ion-Selective Electrodes with Highly Selective Thioamide Derivatives of <i>p</i>-<i>tert</i>-Butylcalix[4]arene for the Determination of Lead(II) in Environmental Samples
Thioamide derivatives of <i>p</i>-<i>tert</i>-butylcalixÂ[4]Âarene were used as ionophores in the development of
solid-contact ion-selective electrodes based on conducting polymer
polyÂ(3,4-ethylenedioxythiophene)/polystyrene sulfonate (PEDOT/PSS)
which was synthesized by electrodeposition on the glassy carbon electrodes.
The typical ion-selective membranes with optionally two different
plasticizers [bisÂ(2-ethylhexyl)Âsebacate (DOS) and 2-nitrophenyl octyl
ether (NPOE)] were investigated. The potentiometric selectivity coefficients
were determined by separate solution method (SSM) for Pb<sup>2+</sup> over Cu<sup>2+</sup>, Cd<sup>2+</sup>, Ca<sup>2+</sup>, Na<sup>+</sup>, and K<sup>+</sup>. High selectivity toward Pb<sup>2+</sup> was
obtained. By applying two conditioning protocols, a low detection
limit logÂ(<i>a</i><sub>DL</sub>) â â9 was
achieved. The fabricated ion-selective electrodes were used to determine
Pb<sup>2+</sup> concentration in environmental samples. The obtained
results were compared to analysis done by inductively coupled plasma
mass spectrometry (ICPMS)
Reduced Graphene Oxide Films as Solid Transducers in Potentiometric All-Solid-State Ion-Selective Electrodes
The development of ion-selective electrodes (ISEs) using
solid-state
transducer materials is of great interest for advanced potentiometric
detection systems. At present, conducting polymers are the most used
solid-state transducing materials. However, their reliability is strongly
related to their chemical stability and the formation of internal
water films. Here we report on the use of reduced graphene oxide (RGO)
films of different thicknesses as transducer materials in potentiometric
all-solid-state ISEs. First, the transduction mechanism is fully analyzed,
revealing that RGO films act as asymmetric capacitors where their
electron density is in contact with ions of the electrolyte solution,
creating a capacitance due to the constant phase elements present
in the system. Second, as a proof of concept, RGO films are used in
a calcium ISE showing highly reproducible sensing responses and outstanding
increased signal-to-noise ratios with drifts of only 10 ÎŒV/h.
These performance parameters are among the best compared to those
of other ISE transducer materials so far. With its ease of fabrication
and processing into reproducible films of controlled thickness and
ease for further tailoring chemical composition and tailoring electrical
properties, RGO offers great promise as a reliable high-performance
transducer material for solid-state ISE sensors