Metodos instrumentales
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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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Metodos instrumentales

METODOS INSTRUMENTALES

INTRODUCCIÓN


Classification of analytical methods

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


Classical

Classical

  • Qualitative - identification by color, indicators, boiling points,

  • odors

  • Quantitative - mass or volume (e.g. gravimetric, volumetric)


Instrumental

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


Types of instrumental methods

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


Metodos instrumentales

  • 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


Metodos instrumentales

DATA

  • Time - vary with time (frequency, phase, pulse width)

  • Analog - continuously variable magnitude (current, voltage, charge)

  • Digital - discrete values (count, serial, parallel, number*)


Performance characteristics

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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