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METODOS INSTRUMENTALES

METODOS INSTRUMENTALES. INTRODUCCIÓN. Classification of Analytical Methods. Qualitative instrumental analysis is that measured property indicates presence of analyte in matrix Quantitative instrumental analysis is that magnitude of measured

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METODOS INSTRUMENTALES

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  1. METODOS INSTRUMENTALES INTRODUCCIÓN

  2. Classification of Analytical Methods • Qualitative instrumental analysis is that measured property • indicates presence of analyte in matrix • Quantitative instrumental analysis is that magnitude of measured • property is proportional to concentration of analyte in matrix

  3. Classical • Qualitative - identification by color, indicators, boiling points, • odors • Quantitative - mass or volume (e.g. gravimetric, volumetric)

  4. Instrumental • Qualitative - chromatography, electrophoresis and identification by measuring physical property (e.g. spectroscopy, electrode potential) • Quantitative - measuring property and determining relationship to concentration (e.g. spectrophotometry, mass spectrometry) • Often, same instrumental method used for qualitative and quantitative analysis

  5. Types of Instrumental Methods • Property Example Method Radiation emission Emission spectroscopy - fluorescence, phosphorescence, luminescence Radiation absorption Absorption spectroscopy -spectrophotometry, photometry, nuclear magnetic resonance, electron spin resonance • Radiation scattering Turbidity, Raman • Radiation refraction Refractometry, interferometry • Radiation diffraction X-ray, electron

  6. Radiation rotation Polarimetry, circular dichroism • Electrical potential Potentiometry • Electrical charge Coulometry • Electrical current Voltammetry - amperometry, polarography • Electrical resistance Conductometry • Mass Gravimetry • Mass-to-charge ratio Mass spectrometry • Rate of reaction Stopped flow, flow injection analysis • Thermal Thermal gravimetry, calorimetry • Radioactivity Activation, isotope dilution

  7. DATA • Time - vary with time (frequency, phase, pulse width) • Analog - continuously variable magnitude (current, voltage, charge) • Digital - discrete values (count, serial, parallel, number*)

  8. Performance Characteristics How to choose an analytical method? • How good is measurement? • How reproducible? - Precision • How close to true value? - Accuracy/Bias • How small a difference can be measured? - Sensitivity • What range of amounts? - Dynamic Range • How much interference? - Selectivity

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