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lecture 4; Instrumental methods of analysis by Dr, Salma Amir

spectroscopic, electroanalytical and chromatographic methods

salmaamirfcw
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lecture 4; Instrumental methods of analysis by Dr, Salma Amir

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  1. Lecture No. 04Course title:Fundamental Analytical Chemistry Topic: Instrumental methods Course instructor: Dr. Salma Amir GFCW Peshawar

  2. Instrumental methods of Analysis 1. Spectroscopic methods Deals with measuring the interaction between the analyte and electromagnetic radiation (or the production of radiation by an analyte). 2. Electroanalytical methods Deals with measure an electrical property (i.e., potential, current, resistance, amperes, etc.) chemically related to the amount of analyte. 3. Chromatographic methods Chromatographic methods involve more complex samples in which the analyte is separated from interfering substances or mixture.

  3. 1. Spectroscopic methods • More than half of all instrumental methods of analysis involve the absorption or emission of light.Such instrumental methods can be referred to as spectrochemical methods. • The science that deals with light and its absorption and emission by solutions and other material substances is called spectroscopy or spectrometry. • The broad term for the instrument used is spectrometer, while a slightly more specificterm (when a light sensor known as a phototube is used) is spectrophotometer. • In spectrochemicalanalysis procedures, the degree to which light is absorbed, or the intensity of light that is emitted, is related to the amount of an analyte present in the sample tested. Thus the degree of light absorption and the intensity of light emission are the critical measurements. The electrical signal readout referred to in the case of spectroscopy, an electrical signal that is related to the degree of light absorption or the intensity of light emission. The instrument readings are the readings generated by the instrument as a result of this absorption or emission.

  4. General principle of spectroscopic instrument

  5. Classification • It includes the spectral differences between atoms (atomic spectroscopy) and molecules (molecular spectroscopy) 1. UV-Vis spectroscopy 2. IR spectroscopy 3. NMR spectroscopy 4. Raman spectroscopy 5. Atomic absorption spectroscopy 6. Atomic emission spectroscopy 7. Atomic and molecular fluorescence

  6. 2. Electroanalytical methods • Electroanalytical methods involve the measurement of a voltage or current resulting from electrodes immersed into the solution. OR Electroanalytical methods involve the measurement of either the electrical current flowing between a pair of electrodes immersed in the solution tested (voltammetricand amperometric methods) or an electrical potential developed between a pair of electrodes immersed in the solution tested (potentiometric methods). • In either case, the measured parameter (current or potential) is proportional to the concentration of analyte.

  7. Classification 1. Voltammetry and polarography 2. Conductometry 3. Potentiometry 4. Ampherometry 5. Coulometry

  8. 3. Chromatography • Chromatographyis the separation of the components of a mixture based on the different degrees to which they interact with two separate material phases. • The nature of the two phases and the kind of interaction can be varied, giving rise to the different types of chromatography • One of the two phases is a moving phase (the mobile phase), while the other does not move (the stationary phase). • The mixture to be separated is usually introduced into the mobile phase, which then is made to move or percolate through the stationary phase either by gravity or some other force. • The components of the mixture are attracted to and slowed by the stationary phase to varying degrees, and as a result, they move along with the mobile phase at varying rates, and are thus separated.

  9. Classification • Real instrumental chromatography employs highly engineered materials for the stationary phase through which the mobile phase fluid carrying the mixture of analytes passes, with continuous partitioning of the analytes between the two phases. 1. HPLC(High performance liquid chromatography) 2. GC (Gas chromatography)

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