Analysis

• Chromatography


  Measuring the migration rates can identify the compounds without the need of collections
• Chromatographic techniques

  • Liquid phase chromatography (LC)
  • Ion chromatography (IC)
  • Size exclusion chromatography (SEC)
  • Liquid/Liquid chromatography (partition chromatography-LLC)
  • Liquid/bound phase chromatography
  • Gas phase chromatography (GC)
  • Gas/liquid chromatography (GLC)
  • Gas/solid chromatography (GSC)
  • Supercritical fluid chromatography (SPC)
  • Thin layer chromatography (TLC)
• Liquid phase chromatography (LC)


  The mobile phase is a liquid
• Liquid/solid chromatography (absorption chromatography)


  The stationary phase is a solid medium to which the species adhere through the dual effect of physisorption and chemisorption
• Ion chromatography (IC)


  The mobile phase is a buffer solution while the solid stationary phase has a surface composed of ionic sites: the phase allows exchange of their mobile counter ion with ions of the same charge present in the sample
• Size exclusion chromatography (SEC)


  The stationary phase is a material containing pores whose dimension are selected as a function of the size of the species to be separated
• Liquid/Liquid chromatography (partition chromatography-LLC)


  The stationary phase is an immobilized liquid upon an inert and porous material, which has only a mechanical role of support
• Liquid/bound phase chromatography


  To immobilize the stationary phase, covalent bonding to a mechanical support is preferable
• Gas phase chromatography (GC)


  The mobile phase is an inert gas
• Gas/liquid chromatography (GLC)


  The stationary phase is an immobilized liquid, either by impregnation or by bonding to an inert support which can be the inner surface of the column
• Gas/solid chromatography (GSC)


  The stationary phase is a porous solid (graphite, silica, porous alumina) while the mobile phase is a gas
• Supercritical fluid chromatography (SFC)


  The mobile phase is a fluid in a supercritical state (carbon dioxide at about 50°C and more than 150 bar)
• Thin layer chromatography (TLC)


  The principle is similar to HPLC, but the migration of the constituents through the stationary phase is different: Separation is conducted on a thin layer of stationary phase, usually based upon silica gel and deposited on a rectangular plate made out of glass, plastic or aluminium
• Thin layer chromatography (TLC)

  1. A small volume of the sample is put close to the bottom of the plate as a small spot

  2. The plate is put in the developing chamber

  3. The mobile phase rises up the stationary phase by capillarity, moving the components at various rates
• Electrophoresis


  A very sensitive separation method based on the differential migration of the species whether or not they carry an overall electrical charge, present in the sample solution under the effect of an electric field and when supported by an appropriate medium
• Electrophoresis


  1. A strip of plastic material covered with a porous substance (gel) is impregnated with an electrolyte buffer, the extremities are dipped into 2 independent reservoirs with the same electrolyte and linked to electrodes to a voltage supply

  2. The sample is deposited as a transverse band, cooled and bedded between 2 insulating plates
• Ultraviolet and visible absorption spectroscopy


  Based on the interaction of radiation with the samples, absorption, emission, scattering in the 180-1100 nm near UV, visible and very near infrared radiation range
• Spectrophotometer


  Measures the transmittance (or absorbance) as a function of wavelength
• Lambert-Beer law

  A = εlC, where A is the absorbance, ε is the molar absorption coefficient, l is the thickness of the solution, and C is the molar concentration
• Chromophore groups


  For some molecules with the same chromophore, the positions of the absorption bands remain constant
• Infrared spectroscopy


  Identification of compounds and determination of molecular structure
• 1. Ray fluorescence spectrometry


  A very accurate method for quantitative measurements of the elemental composition for all types of samples
• 1. Ray fluorescence spectrometry

  1. X-rays bombard the sample, causing it to emit fluorescence

  2. Photo-ionization of the atom produces an ionized atom

  3. Stabilization of the ionized atom re-emits an X-ray fluorescence photon
• Nuclear magnetic resonance spectroscopy


  Leads to precise information about the structural formula, stereochemistry and conformation of molecules
• Nuclear magnetic resonance spectroscopy


  Collects information about the interactions between the nuclei of certain atoms in the sample when they are subjected to an external very strong static magnetic field and an oscillating magnetic field 10,000 times weaker
• Mass spectrometry


  An analytical method based on the determination of the atomic or molecular masses of individual species present in the sample
• Mass spectrometry


  A quantity of the sample is transferred into the gas phase and ionized, then subjected to external electric/magnetic fields used to separate the components which are finally detected