Remedial and adaptive solutions of ISFET non‐ideal behaviour

Khanna, Vinod Kumar

doi:10.1108/02602281311324681

Cited by 34 publications

(20 citation statements)

References 26 publications

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“…20 samples per minute [26] with a precision of 0.005 pH [27]. The sensors are known to drift between 0.03 and 0.05 pH upon initial deployment, though the exact magnitude of the drift will depend on the ISFET materials and packaging [28]. Long conditioning periods (1.5 months) prior to calibration can reduce this drift [25] and each sensor requires a full individual calibration prior to deployment [29].…”

Section: Ph Sensors For Oceanic Watersmentioning

confidence: 99%

Characterisation and deployment of an immobilised pH sensor spot towards surface ocean pH measurements

Clarke

Achterberg

Rérolle

et al. 2015

Analytica Chimica Acta

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The oceans are a major sink for anthropogenic atmospheric carbon dioxide, and the uptake causes changes to the marine carbonate system and has wide ranging effects on flora and fauna. It is crucial to develop analytical systems that allow us to follow the increase in oceanic pCO2 and corresponding reduction in pH. Miniaturised sensor systems using immobilised fluorescence indicator spots are attractive for this purpose because of their simple design and low power requirements. The technology is increasingly used for oceanic dissolved oxygen measurements. We present a detailed method on the use of immobilised fluorescence indicator spots to determine pH in ocean waters across the pH range 7.6-8.2. We characterised temperature (-0.046 pH/°C from 5 to 25 °C) and salinity dependences (-0.01 pH/psu over 5-35), and performed a preliminary investigation into the influence of chlorophyll on the pH measurement. The apparent pKa of the sensor spots was 6.93 at 20 °C. A drift of 0.00014 R (ca. 0.0004 pH, at 25 °C, salinity 35) was observed over a 3 day period in a laboratory based drift experiment. We achieved a precision of 0.0074 pH units, and observed a drift of 0.06 pH units during a test deployment of 5 week duration in the Southern Ocean as an underway surface ocean sensor, which was corrected for using certified reference materials. The temperature and salinity dependences were accounted for with the algorithm, R=0.00034-0.17·pH+0.15·S(2)+0.0067·T-0.0084·S·1.075. This study provides a first step towards a pH optode system suitable for autonomous deployment. The use of a short duration low power illumination (LED current 0.2 mA, 5 μs illumination time) improved the lifetime and precision of the spot. Further improvements to the pH indicator spot operations include regular application of certified reference materials for drift correction and cross-calibration against a spectrophotometric pH system. Desirable future developments should involve novel fluorescence spots with improved response time and apparent pKa values closer to the pH of surface ocean waters.

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Section: Ph Sensors For Oceanic Watersmentioning

confidence: 99%

Characterisation and deployment of an immobilised pH sensor spot towards surface ocean pH measurements

Clarke

Achterberg

Rérolle

et al. 2015

Analytica Chimica Acta

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“…As they are ingested in the same way as capsules or tablets and move freely through the gut, they generate profiles that provide valuable information about the physiological transit conditions of solid oral dosage forms. A major drawback of pH-sensing telemetric capsules is the pH drift of the commonly applied ion-selective field effect transistor (ISFET) sensors (Khanna, 2013). This effect is typically minimized by drift correction based on post-calibration results (Abbas et al, 2014).…”

Section: Telemetrymentioning

confidence: 99%

Exploring gastrointestinal variables affecting drug and formulation behavior: Methodologies, challenges and opportunities

Hens

Corsetti

Spiller

et al. 2017

International Journal of Pharmaceutics

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(2017) Exploring gastrointestinal variables affecting drug and formulation behavior: methodologies, challenges and opportunities. International Journal of Pharmaceutics, 519 (1-2). pp. 79-97. ISSN 1873-3476Access from the University of Nottingham repository: http://eprints.nottingham.ac.uk/39960/1/FinalVersion-Revised-FOR_EPRINTS_1_YEAR_EMBARGO_ELSEVIER.pdf Copyright and reuse:The Nottingham ePrints service makes this work by researchers of the University of Nottingham available open access under the following conditions. This article is made available under the Creative Commons Attribution Non-commercial No Derivatives licence and may be reused according to the conditions of the licence. For more details see: http://creativecommons.org/licenses/by-nc-nd/2.5/ A note on versions:The version presented here may differ from the published version or from the version of record. If you wish to cite this item you are advised to consult the publisher's version. Please see the repository url above for details on accessing the published version and note that access may require a subscription. After oral intake, a drug formulation is challenged by several gastrointestinal (GI) barriers. Complex variables such as pH, GI secretions and GI transit/motility along the GI tract can affect drug release and absorption in a positive or negative way depending on the physicochemical properties of the drug compound (e.g. pH/pKa interplay for ionizable drugs) and/or the formulation characteristics (e.g. pHsensitive coating). In addition, inter-subject variability in characteristics of the GI environment may cause variable drug absorption and systemic drug availability (Riethorst et al., 2015). Determining the median and range for specific GI variables, and understanding how they influence oral drug behavior along the GI tract, will be helpful in the field of drug development. 2The present review provides an overview of different methodologies that can be applied to study physiological variables of the human GI tract and their impact on oral drug absorption in healthy and patient populations. The methodologies have been subdivided into two groups: (i) noninvasive and (ii) invasive methodologies. Although some of the methodologies are more historical than operational, they have been of paramount importance for innovations in drug and formulation development; in addition, they have created the basis for several novel methodologies, leading to an in-depth comprehension of different GI variables: gastric emptying (magnetic resonance imaging (MRI), scintigraphy, acetaminophen absorption technique, ultrasonography, breath test, intraluminal sampling and telemetry), motility (MRI, small intestinal/colonic manometry and telemetry), GI volume changes (MRI and ultrasonography), temperature (telemetry) and GI pH (intraluminal sampling and telemetry). Noninvasive methodologiesa. Scintigraphy Disturbances in the normal movement of food along the GI tract can be associated with abdominal pain, early satiety and nausea. Measurement of GI transit, es...

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“…In other words, our experimental results of 55.7 mV/pH for the oxygen-plasmatreated CNTFs present a much better response with respect to the as-sprayed CNTFs. Moreover, as compared to other pH sensing platforms, such as Si 3 N 4 -gated ISFET [7] and SiO 2 -gated ISFET [8], the oxygen-plasma-treated CNTFs demonstrate the higher pH voltage sensitivity and larger linearity which can accurately respond to the ions of interest in different pH levels.…”

Section: Resultsmentioning

confidence: 98%

Functionalized Carbon Nanotube Thin Films as the pH Sensing Membranes of Extended-Gate Field-Effect Transistors on the Flexible Substrates

Tsai

Huang

Wang

et al. 2014

IEEE Trans. Nanotechnology

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The oxygen-plasma-functionalized carbon nanotube thin films on the flexible substrates as the pH sensing membranes of extended-gate field-effect transistors are proposed for the first time. The carbon nanotubes are ultrasonically sprayed onto the polyimide substrates followed by an oxygen-plasma functionalization. Such oxygen-plasma-treated carbon nanotube thin films (CNTFs) exhibit superior pH sensing characteristics with the sensitivity of 55.7 mV/pH and voltage linearity of 0.9996 in a wide sensing range of pH 1-13. Moreover, the excellent flexibility of carbon nanotube is also demonstrated and the oxygen-plasma-treated CNTFs still maintain the sensitivity of 53.6 mV/pH and voltage linearity of 0.9943 even after five-cycle bending test. These results reveal that the oxygen-plasma-treated CNTFs have great potentials in the practically disposal and wearable biosensor applications.Index Terms-Biosensors, carbon nanotube (CNT), extendedgate field-effect transistors (EGFETs), flexible substrates.

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Remedial and adaptive solutions of ISFET non‐ideal behaviour

Cited by 34 publications

References 26 publications

Characterisation and deployment of an immobilised pH sensor spot towards surface ocean pH measurements

Characterisation and deployment of an immobilised pH sensor spot towards surface ocean pH measurements

Exploring gastrointestinal variables affecting drug and formulation behavior: Methodologies, challenges and opportunities

Functionalized Carbon Nanotube Thin Films as the pH Sensing Membranes of Extended-Gate Field-Effect Transistors on the Flexible Substrates

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