Lecture 4: Electroanalytical Methods Zulkarnain Mohamed Idris PTT 202 Organic Chemistry for Biotechnology firstname.lastname@example.org Semester 1 2013/2014
Introduction • The electrical properties of a solution depends on the nature of the components and their concentrations that permit qualitative and quantitative methods of analysis to be developed. • The electrical properties of solution are measured using electrodes in the arrangements known as electrochemical cells. Two main types of electrochemical cells: Electrolytic and voltaic or galvanic cells
Electrolytic Cells • A current will flow between the two electrodes when a potential difference is applied across those two electrodes that dip into a solution. • The amount of current flows depends upon the voltage applied and the electrochemical properties of the solutions. • The total amount of chemical changes which takes place at an electrode is related to the total amount of current which forms the basis of coulometric methods of analysis.
Voltaic or Galvanic Cells • The chemical nature of the electrodes and solutions results in chemical reaction taking place at the electrodes and solutions with the production of electrical energy without the need for external voltage. • Develop a potential relative to the solution due to the nature of the electrode and the solution. • This potential can be measured and related to the concentration of ions in the solution.
Biosensors • Are analytical devices that incorporate a biological component and a transducer. • The biological component immobilized on to the transducer. • Available in disposable forms for example measurement of blood glucose in diabetic patients and evaluation of the freshness of uncooked meat. • Others designs are suitable for continuous use such as on-line monitoring of fermentation process and detection of toxic substances.
Biosensor Components:Biological Components • Can be divided into two main categories: biocatalysts and bioreceptors. • Function: to recognize and bind a specific analyte. • The properties of the biological components give the specificity to biosensors and make them suitable for the analysis of samples without pre-treatment. • Biocatalysts: binding followed by chemical reactions and released of products. • Bioreceptors: binding is non-catalytic and essentially irreversible.
Biosensor Components:Transducers • Converts the reaction between the analyte and the biological component into electrical signal which is a measure of the concentration of the analyte. • A wide range of transducers are available and can be divided into electrochemical, optical, thermal and piezoelectrical.
Electrochemical Biosensor Fc+= ferricinium Fc= ferrocene Glu Ox=Glucose oxidase