NMR and Mass Spectrometry Flashcards

Flashcards for NMR and Mass Spectrometry Review

What are the fundamental concepts of NMR?

Magnetic field aligns nuclei, RF pulse tips nuclei, nuclei precess giving off rf signal, nuclei realign with the field.

Which nuclei possess spin?

Nuclei with odd mass or odd atomic number.

What is the Larmor Frequency equation?

(\omega = \gamma B_0), where γ is gyromagnetic ratio and B₀ is field strength.

What is population difference governed by?

Governed by Boltzmann distribution, determines signal strength.

What units are Chemical Shifts measured in and what do they reflect?

ppm, reflects electronic environment of nuclei.

What units are Coupling Constant measured in and what do they indicate?

Hz, indicates spin-spin interactions.

What is Spin-Lattice Relaxation (T₁)

Time constant for energy transfer to surroundings.

What is Spin-Spin Relaxation (T₂)

Time constant for loss of phase coherence.

What does the Multiplicity Rule state?

N equivalent neighboring protons split signal into N+1 peaks

What is the function of Superconducting Magnets?

Generate strong, stable magnetic fields.

What is the function of Shim Coils?

Correct magnetic field inhomogeneities.

What is the function of Lock Systems?

Compensates for field drift over time.

What is the function of RF Transmitter/Receiver?

Excites nuclei and detects resulting signals.

What does the Probe contain?

Contains sample and RF coils.

What is Free Induction Decay (FID)?

Time-domain signal collected after pulse.

What does Fourier Transform do?

Converts time-domain to frequency-domain spectra.

What do Window Functions do?

Modify FID to enhance resolution or sensitivity.

Why are Phase and Baseline Correction important?

Essential for accurate spectral interpretation.

What does Integration provide?

Provides information about the number of nuclei.

What do Exchange Phenomena cause?

Dynamic processes cause line broadening and coalescence.

List examples of 2D NMR techniques?

COSY, HSQC, HMBC, NOESY.

What is NOE and why is it important?

Distance-dependent through-space interaction, crucial for structural determination.

What is Mass-to-Charge Ratio (m/z)?

Primary measurement in mass spectrometry.

What is Resolution in mass spectrometry?

(R = m/\Delta m), ability to separate closely spaced peaks.

What is the difference between Exact and Nominal Mass?

Exact mass considers isotopic composition; nominal uses integers.

What does the Nitrogen Rule state?

Odd nominal mass indicates odd number of nitrogen atoms.

What is the formula for Double Bond Equivalent?

(DBE = 1 + \frac{1}{2}\sum Ni(Vi-2))

Describe Electron Impact (EI)

Hard ionization, creates fragments, useful for small molecules.

Describe Chemical Ionization (CI)

Soft ionization, shows molecular ion, less fragmentation.

Describe Electrospray Ionization (ESI)

For large biomolecules, multiple charging.

Describe MALDI

Matrix-assisted laser desorption/ionization, ideal for proteins and polymers.

Describe FAB

Fast Atom Bombardment, useful for polar and ionic compounds.

How do Magnetic/Electrostatic mass analyzers work?

Uses magnetic fields to separate ions by m/z.

How does a Quadrupole mass analyzer work?

Uses oscillating electric fields, filters ions by stability.

How does Time-of-Flight (TOF) mass analyzer work?

Measures flight time through drift tube.

How does FT-ICR mass analyzer work?

Uses cyclotron frequency in magnetic field, highest resolution.

How does Ion Trap mass analyzer work?

Captures ions in 3D trap, allows MS^n capabilities.

What do Isotope Patterns aid in?

Aid in element identification.

What do Fragmentation Patterns provide?

Provide structural information.

What are GC-MS and LC-MS?

Combined techniques for complex mixtures.

How is Quantitative Analysis done?

Using internal standards and calibration curves.

What are Proteomics Applications used for?

Protein identification and sequencing.