Mass Spec Flashcards
What is Mass Spectrometry (MS) used for?
To identify the identity, molecular mass, elemental composition, and chemical structure of an unknown compound.
What are the two types of Mass Spectrometry?
- Atomic Mass Spectrometry
- Molecular Mass Spectrometry
What occurs to the analyte in mass spectrometry?
The analyte is converted to ions by applying energy.
What is the Mass-to-Charge Ratio?
A unitless ratio of the mass number to the number of charges present on the ion.
True or False: For a single charged atom, the mass-to-charge ratio is equivalent to the mass.
True
Define Mass Spectrum.
The number of ions (abundance) plotted against the mass-to-charge ratio.
What is Relative Abundance in mass spectrometry?
The quantity of positively charged fragments that reached the detector.
What is the Base Peak?
The most intense (tallest) peak, indicating the ion with the greatest relative abundance.
What does the Molecular Ion Peak represent?
The molecular mass of the whole compound and is also the heaviest ion.
What is the atomic mass scale based on?
A specific isotope of carbon.
What is the unit for atomic mass?
Dalton (Da)
What is Average Atomic Mass?
The sum of the exact mass of each isotope weighted by its fractional abundance in nature.
What is Average Molecular Mass?
The sum of the atomic mass of the atoms in the formula of a compound.
Define Mass Number.
Atomic or molecular mass expressed without units.
What is the function of a vacuum system in mass spectrometry?
To maintain low pressure in all components, ensuring low collision frequency.
What is a Mass Spectrometer?
An analytical instrument that produces, separates, and detects ions to generate a mass spectrum.
What is the Inlet System in mass spectrometry?
Where a micro amount of sample is introduced.
What is the Ionization Source’s role?
Bombards the samples with photons to convert them to gaseous ions.
What does the Mass Analyzer do?
Separates ions based on mass-to-charge ratio.
What is the function of the Detector in mass spectrometry?
Collects and converts the data into an electric signal.
What is the purpose of ionization techniques in mass spectrometry?
To form gaseous analyte ions.
What is the required resolution in mass spectrometry?
Depends on compounds of the same nominal mass.
Define Magnetic Sector Analyzer.
Separates ions with different masses but constant kinetic energy based on deflection in a magnetic field.
What is a Double-focusing Mass Spectrometer?
Similar to a magnetic sector analyzer but includes an electric sector that precedes the magnetic sector.
What is the Quadrupole Mass Analyzer composed of?
4 cylindrical rods connected to DC and RF voltages.
What is the principle of Time-of-Flight (TOF) Mass Analyzers?
Ions with nearly identical kinetic energy enter a field-free region, with velocity depending on mass.
What is the main advantage of TOF Analyzers?
Nearly unlimited mass range.
What is the Electron Multiplier?
The most common transducer in mass spectrometry, multiplying secondary electrons.
What are the two types of Electron Multipliers?
- Discrete Dynode Electron Multiplier
- Continuous Dynode Electron Multiplier
How does the Discrete Dynode Multiplier function?
An ion beam strikes a dynode, producing secondary electrons that hit subsequent dynodes.
What is a Faraday Cup used for?
To measure the current proportional to the number of ions colliding with a collector plate.
What are Microchannel Plate Arrays?
An array of miniature electron multipliers arranged parallel to each other.
What is Inductively Coupled Plasma (ICP)?
Consists of 3 concentric quartz tubes wherein Argon streams flow at a rate of 11-17 L/min.
What does ICP stand for in Atomic Mass Spectrometry?
Inductively Coupled Plasma
ICP is a technique used to convert samples into gaseous ions for analysis.
What are the components of Inductively Coupled Plasma (ICP)?
3 concentric quartz tubes
Argon streams flow through these tubes at a rate of 11-17 L/min.
How is Argon ionized in ICP?
By a spark from a tesla coil.
What are the two main types of sample introduction in ICP?
- Solution samples (using nebulizer)
- Solid samples (dissolved or volatilized)
What is the pressure condition for ICP and mass spectrometer operation?
ICP operates at atmospheric pressure; mass spectrometer operates at high vacuum.
What is the purpose of the sampler and skimmer in ICP?
Allows passage of ions through an orifice (~1 mm).
What is the role of calibration curves in ICPMS?
They relate the ratio of analyte and internal standard to concentration.
What are the two types of ionization sources mentioned in Atomic Mass Spectrometry?
- Spark Source Mass Spectrometry (SSMS)
- Glow-discharge Mass Spectrometry (GDMS)
What is differential pumping?
Multiple pumps create a pressure gradient causing the analyte to flow from high-pressure to low-pressure.
What are spectroscopic interferences in mass spectrometry?
Interferent ions have the same m/z value as the analyte ion.
What causes matrix interferences in mass spectrometry?
A reduction in signal when concentration exceeds 500 to 1000 µg/mL.
What industries utilize ICPMS for analysis?
- Semiconductor and electronics industry
- Geochemistry
- Biological and medical research
What is the detection limit for quadrupole ICPMS?
Lower than 1 ppb.
What is the base peak in molecular mass spectrometry?
The relative intensity is set at 100%.
What are the two main categories of ion sources in mass spectrometry?
- Gas-phase sources
- Desorption sources
What is the most commonly used ionization source?
Electron Ionization Source (EI).
What is a key characteristic of Chemical Ionization Source (CI)?
Produces less energy than EI.
What is Fast Atom Bombardment (FAB) used for?
Applicable to non-volatile and thermally unstable samples.
What is Matrix-Assisted Laser Desorption/Ionization (MALDI) primarily used for?
Applicable to non-volatile compounds such as proteins and oligonucleotides.
How does Electrospray Ionization (ESI) work?
Strong electric field is applied to a liquid sample, forming highly charged droplets.
What are ambient sampling and ionization sources?
Uses established ionization methods in an open-air, direct ionization environment.
What type of samples can be introduced using batch inlet systems?
Solid, liquid, or gas samples.
What is the purpose of inlet systems in molecular mass spectrometry?
Introduces the sample to the ion source and ensures minimal loss of vacuum.
Name the types of inlet systems used in molecular mass spectrometry.
- Batch inlets
- Direct Probe inlets
- Chromatographic and Electrophoretic inlets
What is a batch inlet system?
The simplest and most common inlet system where the sample is volatilized externally and allowed to leak into the evacuated ionization region.
How does a batch inlet system work?
- Liquid sample is injected using a microsyringe
- Gas sample is enclosed in a metered area
- Reservoir and tubing are heated at high temperatures to volatilize the liquid
- Samples are leaked through the ionization source
What is a direct probe inlet system?
The sample is volatilized inside the probe and is applicable for small samples of solids and non-volatile liquids.
How does a direct probe inlet system work?
- Samples are injected through a probe
- The probe is placed extremely close to the ionization source
- It enters through a slit that leads to the spectrometer
What is the function of a chromatographic and electrophoretic inlet system?
Couples the mass spectrometer with another instrument such as GC to analyze mixtures.
What is the most commonly used mass analyzer in GC/MS systems?
The quadrupole mass analyzer.
What types of higher resolution spectrometers are used for fragmentation pattern analysis?
- Magnetic sector
- Double Focusing
- Time-of-Flight
- Fourier Transform
What is tandem mass spectrometry?
A combination of two mass spectrometers, also called Mass spectrometry-Mass spectrometry (MS/MS).
What information can be obtained from a mass spectrum of a pure compound?
- Molecular mass
- Molecular formula
- Presence or absence of functional groups
- Actual identity of the compound
What are the components of tandem mass spectrometry?
- Original Ions
- Precursor Ion
- Product Ions
What are the types of spectra produced in tandem mass spectrometry?
- Product-Ion Spectra
- Precursor-Ion Spectrum
- Natural Loss Spectrum
- Three dimensional MS/MS Spectrum
What are hyphenated methods in mass spectrometry?
Combination of two or more analytical methods to produce a more efficient one.
What are examples of hyphenated methods?
- GC/MS
- LC/MS
- Tandem MS
- GC/MS/MS
- LC/MS/MS
True or False: Mass spectrometry can analyze complex mixtures effectively.
True
In what scenarios is LC/MS particularly useful?
For the analysis of samples with non-volatile components.
