Exam 1 Flashcards
3 ionization methods
- gas-phase
- desorption
- evaporative
Electron Impact
-gas-phase ionization method
-M+ ion formed
-Advantages: Data base searchable, structural information
-Disadvantages:
M+ occasionally absent
Chemical Ionization
- gas-phase ionization method
- M+1, M+18 formed
- Advantage: M+ usually present
- Disadvantage: Little structural information
Field Desorption
- Desorption Ionization method
- M+ formed
- Advantage: Nonvolatile compounds
- Disadvantage: Need specialized equipment
Fast Atom Bombardment
-Desorption ionization method
-M+1, M+ matrix, M+ cation formed
-Advantage: Nonvolatile Compounds, sequencing information
Disadvantage: Matrix interference, difficult to interpret
Plasma Desorption
- desorption ionization method
- M+
- Advantages: Nonvolatile Compounds
- Disadvantages: Matrix interference
Laser Desorption
- Desorption method
- M+1, M+ matrix
- Advantages: Nonvolatile compounds, bursts of ions
- Disadvantages: matrix interference
Thermospray
- Evaporative method
- M+
- Advantages: Nonvolatile compounds
- Disadvantages: Outdated
Electrospray
- Evaporative method
- M+, M++, M+++
- Advantages: Nonvolatile compounds interfaces with LC, forms multiply charged ions
- Disadvantages: limited classes of compounds, little structural information
5 types of mass analyzers
- Magnetic Sector
- quadrupole
- ion trap
- time of flight
- fourier transformation
Magnetic Sector
- Mass Range: 1-15000 m/z
- Resolution: 0.0001
- Sensitivity: Low
- Advantage: High resolution
- Disadvantage: Low sensitivity, very expensive, high technical expertise
Quadrupole
- Mass range: 1-5000 m/z
- Resolution: Unit
- Sensitivity: High
- Advantages: easy to use, inexpensive, high sensitivity
- Disadvantages: Low resolution, low mass range
Ion trap
- Mass Range: 1-5000 m/z
- Resolution: Unit
- Sensitivity: High
- Advantages: easy to use, inexpensive, high sensitivity, Tandem (MS)
- Disadvantages: low resolution, low mass range
Time of Flight
- mass range: unlimited
- resolution: 0.0001
- sensitivity: high
- advantages: high mass range, simple design
- Disadvantage: very high resolution
Fourier Transform
- mass range: up to 70 kDa
- resolution: 0.0001
- sensitivity: high
- advantage: very high resolution and mass range
- disadvantage: very expensive, high technical expertise
5 common features of mass spectrometer
1. Computer System 2, Sample Introduction 3. Ionization Method 4. ion separation method 5. detector
How does hydrogen bonding affect infrared spectroscopy
Alters the stretching and bending vibrations
2 Types of IR
- Dispersion IR
- Fourier Transform
Important factors to consider when preparing an IR sample
- liquid can be neat or in solution
- solutions handled in cells of 0.1-1 mm thickness
- solvent must be dry and transparent in region of interest
- solids can be examined as mull, pressed disk, glassy film, or as powders
requirements for data to consider before interpreting IR
- spectrum must be adequately resolved and of adequate intensity
- spectrum should be of reasonably pure compound
- spectrometer should be calibrated so bands are observed at proper frequencies or wavelengths
- method of sample handling must be specified
