ochem 2 conceptual

molecule seperation techniques

chromatography or chromatogram

Ionization- fragmentation causes a cation and radical fragment ion

Electron Impact (g) (lots of fragmentation) , Chemical ionization (g) (some) , Electrospray (l) (very little), and MALDI (s) (some)

Electron Impact

electron bombards analyte causing loss of electron M + e- —> M(+) + radical + 2 e-

Chemical Ionization

softer ionization, like EI, less fragments, used to determine the molecular weight of organic compounds with very little breakdown or fragmentation.

Electron Spray

soft method of ionization, HPLC or HPCE achine removes electrons from droplets and mist is filtered and like charges seperate. used in mass spectrometry (MS) to turn liquid chemical samples into gas-phase ions. Rather than harsher methods like electron impact (EI) ionization which bombard molecules with high-energy electrons and shatter them into fragments, ESI allows organic chemists to analyze large, polar, or chemically fragile molecules intact

MALDI

It is a "soft" ionization technique used in mass spectrometry (MS) to analyze large, fragile, or non-volatile organic and biological molecules—such as synthetic polymers, dendrimers, proteins, peptides, and nucleic acids—without causing them to break apart

Ion Separation

Quadropole,Time of flight, and Ion trap

Quadropole

• Structure: It consists of four parallel cylindrical metal rods arranged in a square configuration. [1, 2, 3]

• Mechanism:

  • Opposing pairs of rods are electrically connected.

  • The instrument applies a combination of direct current (DC) and alternating radio frequency (RF) voltages to the rods.

  • This creates an oscillating electric field that selectively stabilizes ions of a specific mass-to-charge ratio (m/z) while making other ion paths unstable. [1, 2, 3, 4]

• Function: Ions with the target m/z ratio follow a stable trajectory all the way through the rods to the detector, while unwanted ions crash into the metal rods and are discharged. By sweeping or changing the voltages, the quadrupole scans across different masses to build a complete mass spectrum

Time of Flight

a method used inside a mass spectrometer (MS) to separate and identify ions based on how long it takes them to travel through a field-free vacuum tube

Ion Trap

a device that confines gaseous charged molecules (ions) in a small space using oscillating electric and magnetic fields so they can be separated and analyzed by their mass-to-charge ratio

Spectroscopy

atoms and molecules absorb or emit EMR (electromagnetic radiation), pattern of absorption is spectra, spectroscopy is interpretation of spectra in terms of atomic/molecular structure

types of spectroscopy

IR, NMR, Mass Spec, UV

IR

measures the bond vibration frequencies in a molecule and is used to determine the functional group, based on bond strength and mass, bond polarity.

NMR

analyzes the spin of hydrogen and carbon molecules, radio waves

Mass Spec

fragments the molecule and measures their mass