Brief Overview of Electrochemical Sensors TYPES OF ELECTROCHEMICAL

Brief Overview of Electrochemical Sensors TYPES OF ELECTROCHEMICAL SENSORS Amperometric / Voltammetric sensors: measure current at constant / varied potential: I = f( C ) • Bare electrodes : - Detection of heavy and toxic metal ions by anodic stripping voltammetry. - Detection of organic contaminants, biological compounds and drugs following FIA or HPLC separation. Sotiris Sotiropoulos, Chemistry Department, Aristotle University of Thessaloniki

Brief Overview of Electrochemical Sensors TYPES OF ELECTROCHEMICAL SENSORS Amperometric / Voltammetric sensors • Modified electrode sensors: - Enzyme-modified electrodes (e. g. glucose, penicillin sensors etc). - Immunosensors (antigen-modified electrodes). - DNA sensors. • Gas sensors: - Membrane-covered (Clark-type) sensors (e. g. oxygen, CO, H 2 sensors, ethanol sensor-breathalyzer). - Fuel-cell or battery-type sensors (same applications as above). - Solid-state sensors. Sotiris Sotiropoulos, Chemistry Department, Aristotle University of Thessaloniki

Brief Overview of Electrochemical Sensors TYPES OF ELECTROCHEMICAL SENSORS Potentiometric sensors: measure potential (usually open circuit) under constant (usually 0) current: E = f( C ) • Ion-selective electrodes (ISEs): - Glass electrodes (e. g. p. H-meter, Na+, K+, Li+ sensors). - Solid membrane electrodes (e. g. based on Ag. X for X-, and Ag 2 S for other M+). - Liquid membrane electrodes (e. g. containing a ligand for M+ complexation e. g. Ca+ and K+ sensors). Sotiris Sotiropoulos, Chemistry Department, Aristotle University of Thessaloniki

Brief Overview of Electrochemical Sensors TYPES OF ELECTROCHEMICAL SENSORS Potentiometric sensors • Potentiometric gas sensors: - p. H-meter-based gas detectors (e. g. CO 2, NH 3 etc). - Solid oxide sensors (e. g. zirconia-based O 2 sensor (λ-sensor)). Sotiris Sotiropoulos, Chemistry Department, Aristotle University of Thessaloniki

Brief Overview of Electrochemical Sensors TYPES OF ELECTROCHEMICAL SENSORS Conductometric sensors: measure sample conductivity : σ = f( C ) • Solution conductivity meters: Total salinity measurements. • Semiconductor gas sensors: Change in conductivity upon gas adsorption. • Diode gas sensors: Change of conducting polymer electronic state upon gas adsorption. Sotiris Sotiropoulos, Chemistry Department, Aristotle University of Thessaloniki

Brief Overview of Electrochemical Sensors ADVANTAGES OF ELECTROCHEMICAL SENSORS • Cheap to manufacture. • Simple to use. • • Robust design. • Amenable to miniaturization. Good sensitivity and selectivity (in advanced versions). Sotiris Sotiropoulos, Chemistry Department, Aristotle University of Thessaloniki

Brief Overview of Electrochemical Sensors EXAMPLES OF ELECTROCHEMICAL SENSORS Heavy and toxic metal ion determination in natural waters by anodic stripping voltammetry Carbon paste electrode. Cd(II) and Pb(II) determination in tap water. Cd+++2 e- Cd (pre-concentration); Cd Cd+++2 e- (stripping) L. Baldrianova, I. Svancara, S. Sotiropoulos, Analytica Chimica Acta 599 (2007) 249– 255 Sotiris Sotiropoulos, Chemistry Department, Aristotle University of Thessaloniki

Brief Overview of Electrochemical Sensors EXAMPLES OF ELECTROCHEMICAL SENSORS Detection of biological compounds following their HPLC separation Aminoacid analysis Flow-cell electrochemical detector (via their elecrooxidation: Red Ox +ne-) A. Pappa-Louisi, P. Balkatzopoulou, S. Sotiropoulos J. Liq. Chrom. & Rel. Technol. , 31: 1434– 1447, 2008 Sotiris Sotiropoulos, Chemistry Department, Aristotle University of Thessaloniki

Brief Overview of Electrochemical Sensors EXAMPLES OF ELECTROCHEMICAL SENSORS Membrane-covered amperometric gas sensors. Clark-type cells for O 2 determination in waters, biological fluids and controlled/confined atmospheres (via oxygen electro-reduction: O 2+4 e-+4 H+ 2 H 2 O) Biomedical Sensors Ltd Clark, L. C. et al , J. Appl. Physiol. , 6 (1953) 189 (conjuctival oxygen determination) Sotiris Sotiropoulos, Chemistry Department, Aristotle University of Thessaloniki

Brief Overview of Electrochemical Sensors EXAMPLES OF ELECTROCHEMICAL SENSORS Enzyme-covered amperometric sensors: Glycose determination in blood. 2 e. E L E C T R O D E H 2 O 2 ENZYME [Ox] ENZYME [Red] Glycose Glyconolactone O 2 2 e. Sotiris Sotiropoulos, Chemistry Department, Aristotle University of Thessaloniki

Brief Overview of Electrochemical Sensors EXAMPLES OF ELECTROCHEMICAL SENSORS Enzyme-covered amperometric sensors: Glycose determination in blood. e- E L E C T R O D E MEDIATOR [Red] ENZYME [Ox] ENZYME [Red] Glycose Glyconolactone MEDIATOR [Ox] Sotiris Sotiropoulos, Chemistry Department, Aristotle University of Thessaloniki