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Instrumental Analysis

Instrumental Analysis

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Instrumental Analysis

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  1. Instrumental Analysis CHEM 402 Spring 2007

  2. Chemical Methods of Analysis • Wet chemistry • Quantitative analysis • Qualitative analysis • Titration • Phase change • pH • Analyte concentration • Physical properties • Color changes • Instrumental Analysis

  3. Sun dial, watch Thermometer, thermocouple Barometer, pressure transducer Spectrometer, spectrophotometer Chromatograph Electrochemical techniques Balance Kinetics Mass Spectrometry Time Temperature Pressure Light interactions Chemical separations Electrical properties Mass Rate of Reaction Mass/Charge Instrumental Methods of Analysis Property Classical Instruments

  4. Machine A mechanically, electrically, or electronically operated device for performing a task. Often does not have output data Instrument A measuring device for determining the precise value of a quantity under observation. Must give feedback of some form Instrument vs. Machine

  5. Instrumental Methods • Four Categories • Spectroscopy • Light/sample interaction • Separations • Purification and qualitative • Electrochemical Methods • Interaction of charges/ions • Miscellaneous Techniques

  6. Spectroscopy • Absorbance • Reflection • Emission • Spin • Raman • Scattering • Fluorescence • Phosphorescence • Harmonic techniques • Surface analysis

  7. Separations • Chromatography • chemical interaction separation • Crystallization • liquid/solid phase change • Distillation • liquid/vapor phase change • Electrophoresis • charge difference with physical separation

  8. Electrochemical Methods • Interaction of charges and ions • pH (ion selective electrode) • Voltammetry • Coulometry • Amperometry • Stripping • Other techniques (quant)

  9. Miscellaneous Techniques • Thermal • Digital Scanning Calorimetry (DSC) • Thermal Gravametric Analysis (TGA) • Kinetic • Rate Determination • Diffusion • Reaction order • Mass Spectrometry (MS) • Mass/charge

  10. Miscellaneous Techniques (cont’d) • Rheology • Flow behavior • Thermo-elastic properties • Stress/strain analysis • Ionization • Matrix Assisted Laser Desorption/Ionization (MALDI) • Electron Impact (EI) • Chemical Ionization • Fast atom bombardment (FAB) • Electrospray Ionization (ESI)

  11. Miscellaneous Techniques (cont’d) • Hyphenated techniques • Take advantage of two or more methods/properties of single methods to obtain multiple sets of data from one sample • GC-MS • MS-MS • NMR-NMR (2D NMR)

  12. Instrumentation Response/ Readout Stimulus/ Energy Sample

  13. Instrumental Methods of Analysis • Variables in instrumental analysis • Cost • $ • Energy • Sample • Speed (of analysis) • Limits of Detection • Reproducibility • Amount of sample needed • Effort of analyst • Availability

  14. Electrical Analog current, voltage, charge… Time frequency, phase, pulse width… Digital count, serial, parallel Non-Electrical Physical characteristics length, pressure, … Chemical characteristics radioactivity, density, … Instrumental Methods of Analysis Two domains are present in analysis A ruler can measure length graduated cylinder for volume

  15. Analog • Magnitude of one of the electrical quantities • Voltage, current, charge, power • Continuous in time and amplitude • Typical analog signals • Independent variables • Time • Wavelength (λ, Å, cm-1) • Temperature • Pressure • Susceptible to electronic noise from nearby circuitry

  16. Time • Time relationship of signal fluctuations rather than amplitude of signals • Signal corresponds to HI or LO from decided threshold • frequency data, and periodicity.

  17. Digital • Two-level scheme. (on/off switch) • Each piece of data is a bit • Bits not always useful • Binary data • encode (using power of 2) data into time frames • 210 =1024 (0000000000 to 1111111111) all contained within 10 “frames” of data • Uses linear combination of bits. • Modern computers/modems/pictures…