Integrated optical sensors based on refractometry of ion-selective membranes

2012

The aim of this work was to develop cation-sensors of clinical interest, i.e. potassium, calcium, magnesium sensors. Initially, new PVC based selective membranes were obtained. The potassium sensor using benzo18-crown 6 shows a slope of 57.51 mV.dec -1 , while the calcium sensor using ETH 129 presents a slope of 29.11 mV.dec -1 and the magnesium sensor using benzo-15-crown-5 has a slope of 27.77 mV.dec -1 .

Analytical Chemistry, 2008

A novel type of self-plasticizing polyacrylate-based membrane was developed for all-solid-state ion-selective potentiometric electrodes. The membrane composition contains a conducting polymer (CP): poly(3,4-ethylenedioxythiophene) end capped with methacrylate groups, chemically grafted with the membrane during the photopolymerization step. This composition results in ionselective membranes with the following advantages: lower electrical resistance compared to the CP-free membrane, facile ion-to-electron transduction between the membrane and the electrode support, controlled low activity of analyte ions, and high concentration of interferent ions (incorporated with the CP) within the membrane, potentially resulting in improved analytical parameters. Ca 2+and K + -selective membranes were chosen as model systems to study the effect of pretreatment and CP content on the potentiometric sensor's characteristics. For Ca 2+ sensors, reproducible and stable Nernstian characteristics were obtained within the range from 0.1 to 10 -9 M CaCl 2, without a time-consuming preconditioning step. For K +selective sensors, the influence on Nernstian response range was observed for varying KCl concentrations in the conditioning solution, with the lowest detection limit found close to 10 -8 M KCl. Mass spectrometry coupled with laser ablation studies of the membranes revealed that in this case the detection limit is not related to primary ion content in the membrane contacting a sample solution, but is affected by interfering ion concentration close to the membrane surface.

Analytica Chimica Acta, 2002

An optical strip test to determine calcium is proposed. The membrane consists of a polyester sheet and an active layer composed of a cation-selective neutral ionophore, such as 18-crown-6-ether, a proton selective neutral chromoionophore, such as lipophilised Nile Blue, and potassium tetrakis(4-chlorophenyl)borate as a lipophilic salt. The membrane responds reversibly to calcium ions by an ion-exchange mechanism, changing its colour from blue to red. All experimental variables that influence test strip response, especially in terms of selectivity and response time, have been studied. The system responded linearly in activities in the range 0.046-134 mM. The detection limit is 0.046 mM, the reproducibility intermembrane at a medium level of the range was 8.5%, as relative standard deviation (R.S.D.) of loga Ca 2+ and 2.7% as intramembrane. Calcium was determined by using the test strip proposed in different types of waters (tap, mineral and spring) validating results against a reference procedure. This proposed method for calcium determination in waters is quick (less than 5 min), inexpensive, selective and sensitive and uses only conventional instrumentation.

Analytical Chemistry, 2004

An all-solid-state calcium-selective electrode was constructed with poly(pyrrole) solid-contact doped with calcium complexing ligand Tiron. The potentiometric response of this sensor can have a linear range down to 10-9 M with a slope close to Nernstian and detection limit equal to 10-9.6. The effects of pH and the activity of the interfering ion in the conditioning solution on the potentiometric behavior of the constructed sensors were examined. Potential stability, reproducibility, and impedance studies were performed. The selectivity of the constructed electrode is better than that of the conventional calcium-selective electrode with internal filling solution of 10-2 M CaCl 2 and comparable to that of the best liquid-contact electrodes.

Electrochimica Acta, 2006

Synthetic calix arene-crown ionophores for selective Na + (ionophore L1) and Cs + -ions (ionophore L2) recognition find application in ion-selective membrane electrodes (ISE) for analytical purpose. Selectivity coefficients for the electrodes with compounds L1 and L2 are log K pot Na,Cs = −2.6 and log K pot Cs,Na = −2.4, respectively. Electrodes of two different construction: all-solid-state (ASS) (with conducting polymer layer on glassy carbon or platinum as ion-to-electron transducer) and conventional ion-selective electrode (ISE) (with liquid electrolyte and Ag/AgCl) are presented and their properties and lifetime are being compared. Resistance of PVC membrane with ionophores L1 and L2 were within the range 0.15-1.4 M depending on the type of the outer electrolyte and its concentration. Conductivity of the membranes was in the range 0.7 × 10 −8 to 6 × 10 −8 −1 cm −1 . Warburg coefficients σ were within 0.16 × 10 4 to 12.7 × 10 4 s −1/2 , dielectric constant values ε were in a range 28-60 depending mainly on the type of plasticizer.

Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy, 2015

A novel approach for the determination of Al 3+ from aqueous samples was developed using an optode membrane produced by physical inclusion of Al 3+ selective reagent, which is morin into a plasticized poly(vinyl chloride). The inclusion of Triton X-100 was found to be valuable and useful for enhancing the sorption of Al 3+ ions from liquid phase into the membrane phase, thus increasing the intensity of optode's absorption. The optode showed a linear increase in the absorbance at λ max = 425 nm over the concentration range of 1.85 × 10-6 molL-1 to 1.1 × 10 −4 molL-1 (0.05-3 µg mL-1) of Al 3+ ions in aqueous solution after five minutes. The limit of detection was determined to be 1.04 × 10-6 molL-1 (0.028 µgmL-1). The optode developed in the present work was easily prepared and found to be stable, has good mechanical strength, sensitive and reusable. In addition, the optode was tested for Al 3+ determination in lake water, river water and pharmaceutical samples, which the result was satisfactory.

Membranes, 2020

Ion sensors, conventionally known as ion-selective membrane electrodes, were devised 100 years ago with the invention of a pH electrode with a glass membrane (in 1906 Cremer, in 1909 Haber and Klemensiewicz) [...].

Advanced Functional Materials

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Analytical Chemistry, 2012

Proceedings, 2018

It is demonstrated for the first time that the registration of the optode signal under non-equilibrium conditions reduces analysis time and shifts the sensor working range. The fabrication of optode-like color standards for digital color analysis (DCA) is described, and a multi-parameter color scale for calibration-free sensor arrays is proposed. Advantages and limitations of monochrome and color camera for DCA with colorimetric optodes are discussed.

A second-generation sensor is proposed that aims to enhance both the selectivity and sensitivity of the crown ether system. This sensor uses a calix(4)crown-based ionophore, a receptor that offers a greater affinity for sodium over the simple crown ether receptor. When combined with a switchable dye, this chromoionophore will selectively amplify the refractive index change upon binding sodium over other cations. We shall present the latest developments towards a highly sensitive and selective sodium sensor using a calix(4)crown-based chromoionophore receptor surface.

Analytica Chimica Acta, 1999

Ion-selective optode membranes incorporating calix[4]arene derivatives for cation recognition, and a lipophilic acidochromic dye for transduction have been prepared. The response of the resulting optode membranes has been measured over the range 400-800 nm. Comparisons are made between the analytical performance of a commercially available pH indicator (ETH 5294) and an alternative dye 9-(4-diethylamino-2-octadecanoatestyryl)-acridine with respect to dynamic range, selectivity and stability/lifetime. K exch values and other membrane parameters have been estimated by means of fitting experimental data to theoretically derived equations. (D. Diamond) arenes are already well-established as ionophores for potentiometric ion-selective electrodes. They are frequently chosen because they offer a convenient path to producing ligands that are easily chemically modified. The ligands presented here, tetramethoxy ethyl ester (Ligand 1) and tetraphosphine oxide (Ligand 2) calix[4]arene derivatives, have been reported previously by the authors [3] in ion-selective optode membranes incorporating the acidochromic dye ETH 5294.

Analytical Chemistry, 2002

The development of an integrated analysis system for small ions based on ion-selective optodes and centrifugal microfluidics is reported. The performance of this system was evaluated through five-point calibration plots for two types of optode membranes, one being cation-selective and the other anion-selective, which were incorporated into a microfluidics platform on which fluid motion is induced via angular rotation. Additionally, the application of the microfluidic platform to ion analysis is studied via a two-point calibration protocol used to quantify an unknown sample. Calibrant solutions are delivered from reservoirs fabricated onto the platform to a measuring area that contains the optode membrane, with a change in membrane fluorescence being monitored. This work demonstrates the first instance of a microfluidic-based analysis system with detection based on ion-selective optode membranes monitored with fluorescence transduction. Furthermore, in addition to employing a standard excitation source where a fiber-optic probe is coupled to a tungsten-halogen lamp, laser diodes such as those employed in portable CD/DVD players were studied as excitation sources to enhance the observed fluorescence signals.

Analytica Chimica Acta, 2002

A sensor membrane has been developed for the determination of copper(II) ions that displays excellent performance due to internal referencing of luminescence intensities. The applied sensing scheme (dual lifetime referencing) makes use of the indicator lucifer yellow (LY) and an inert reference luminophore (a ruthenium complex entrapped in polyacrylonitrile beads). Both are contained in a hydrogel matrix. The copper-dependent fluorescence intensity change of LY can be converted in either a phase shift or time dependent parameter. The sensing membrane is capable of determining copper(II) with an outstanding high selectivity over a dynamic range between 1 and 1000 M in neutral or weekly acidic conditions. The advantages of the referencing method over intensity based measurements was demonstrated by the measurement of turbid solutions. The scheme was also applied to two-dimensional measurements in the time domain. Sensor integrated microtiterplates were imaged with a CCD camera gated with square pulses in the microsecond range.

1999

A new type of absorbance-based optical sensor is presented. It is based on a chemical transduction membrane that acts simultaneously as the sensing element and as the light guiding medium. This membrane is inserted between two micromachined waveguides in a silica on silicon structure. Light propagates longitudinally through the membrane, which changes its spectral properties accordingly while interacting with the analyte. As the path length corresponds to the membrane length, not its thickness, high sensitivity can be achieved without an increase of the response time. This paper summarizes the design, the construction, and the validation results obtained with integrated waveguide absorbance optode (IWAO) prototypes. The main advantages of the reported optode are its simple configuration, high sensitivity, and versatility. Experimental results obtained with this IWAO, using a potassium-selective bulk optode, are shown and compared to those obtained with a conventional absorbance device incorporating the same membrane. The optimum membrane thickness of 4 µm gave the lowest light losses (15 dB). The absorbance sensitivities obtained (-0.86 AU/decade) were, as expected, higher than those shown by the conventional device (-0.03 AU/decade), with comparable response times (t 90% ) 0.5 min).