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© SENSORIN 20091 Elicia Wong, PhD Revolutionary Technology in pH Measurement Mar 17-19, 2009.

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Presentation on theme: "© SENSORIN 20091 Elicia Wong, PhD Revolutionary Technology in pH Measurement Mar 17-19, 2009."— Presentation transcript:

1 © SENSORIN Elicia Wong, PhD Revolutionary Technology in pH Measurement Mar 17-19, 2009

2 © SENSORIN L 80 L 400 L 2,000 L 10,000 L Upstream ProcessDownstream Process pH Control Why is it a problem in bioprocessing? Wide Applications: Why is it Important in bioprocessing? Pharmaceutical/biotechnology (medicine) Cosmetic (perfume) Food and beverage (wine, sugar) Water purification & wastewater treatment Petroleum/deep sea/outer space exploration Critical quality parameter for cell and bacterial growth and metabolic activity, productivity and consistency. Drifting Fouling Calibration

3 © SENSORIN Potentiometric pH measurement Outline Existing pH measurement technologies Optical pH measurement Glass electrode Ion-selective field effect transistor (ISFET) New technology Amperometric pH measurement

4 © SENSORIN External reference electrode Measuring electrode High impedance pH meter Glass frit Glass membrane Inner solution Metal wire Voltage difference builds up on the sides of the glass membrane due to difference between H + activities on both sides This voltage difference is measured with the help of an external reference electrode Often reference and measuring electrodes are combined in one single structure Fragile, wet storage, long term drift, requires frequent calibration Potentiometric Approach – Glass electrode Glass frit Inner solution External reference electrode High impedance pH meter Glass membrane Glass electrode

5 © SENSORIN Ion-Selective Field Effect Transistor Vgs Electron path Vds Drain Source Ion-selective interface Insulator External reference electrode Analyte solution Cathode (-)Anode (+) No current flows - -- Current flows H+H+ H+H+ H+H+ Four major components: Source (s), Drain (d), Ion- selective interface and Gate (g). Hydrogen ions at or near the ion-selective interface will cause a variable voltage potential (Vgs – Vds) Solid state device

6 © SENSORIN Photo- detector Optical pH Measurement System Photodetector, optical fiber, sensor Sensor = fluorophore on solid support An incident beam of light is passed to the sensor, where it interacts with the fluorophore. The emitted light intensity is pH dependent Keep in dark (photo- bleaching) Sensor Optical light guide Incident beam Emitted light

7 © SENSORIN Comparison Feature Glass Electrode ISFETOptical Robustness Glass (fragile)Solid state Calibration Required (frequently) Required (longer calibration interval) Required (factory+on site) Stability Drift Maintenance Intensive (wet storage) Easy (dry storage) Intensive (kept in dark (photo- bleaching) Temperature Range Wide Narrow pH range (in ranges) Biological Fouling Occur Sensitivity Low MediumGood

8 © SENSORIN pH-sensitive interface semiconductor Amperometric pH Sensor Counter electrode Internal reference Power supply i V H+H+ H+H+ H+H+ H+H+ VV ii pH-sensitive interface semiconductor H+H+ H+H+ H+H+ H+H+ VV ii pH-sensitive interface + Internal reference External reference electrode Counter electrode Reference electrode Analyte solution pH-sensitive interface

9 © SENSORIN Self-Calibrating pH 4 pH 7 pH 10 Internal reference = pH insensitive molecule pH sensitive molecules Internal reference

10 © SENSORIN Stability chemicallythermally stable Both the proprietary pH sensitive and insensitive molecules are chemically stable (wont leach) and thermally stable (able to withstand high temperature up to 250 C). No degradation in performance with continuous operation and after heat sterilization. Responses were observed after multiple autoclaving cycles (measurement performed after each autoclaving cycle) Continuous operation No degradation in signal with 2-day continuous operation after autoclaving Multiple Autoclaving

11 © SENSORIN Free from Biological Fouling pH detection relies purely on chemical interaction between hydrogen ion and sensing interface rather than membrane diffusion effect (glass electrode) Continuous measurement in medium containing living cells pH insensitive molecules pH sensitive molecules Without pH control Detect change in pH from pH 7.82* to 7.01* *pH verified by off-line pH measurements - H + H+H+ Clotting of glass membrane

12 © SENSORIN Summary Chart Feature Glass Electrode ISFETOptical Amperometric Sensor Robustness Glass (fragile) Solid state Calibration Required (frequently) Required (longer calibration interval) Required (factory) Self calibrated Stability Drift No drift Maintenance Intensive (wet storage) Easy (dry storage) Intensive (Kept in dark (photo- bleaching) Easy (dry storage) Temperature Range Wide NarrowWide pH range (in ranges)0-14 Biological Fouling Occur NO Sensitivity LowMediumGood Ideal for bioprocess pH measurement


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