Podcast
Questions and Answers
What are the two ionization techniques commonly used in CE/MS?
What are the two ionization techniques commonly used in CE/MS?
Electrospray ionization (ESI) and Matrix Assisted Laser Desorption Ionization (MALDI)
What is a major application of CE-MS, especially in biological studies?
What is a major application of CE-MS, especially in biological studies?
Protein and peptide analysis
What is the advantage of CE-MS in terms of volume requirement?
What is the advantage of CE-MS in terms of volume requirement?
It requires minimal volume (nL)
What is the principle behind Inductively Coupled Plasma-Mass Spectrometry (ICP-MS)?
What is the principle behind Inductively Coupled Plasma-Mass Spectrometry (ICP-MS)?
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What is the advantage of ICP-MS spectra compared to conventional ICP optical spectra?
What is the advantage of ICP-MS spectra compared to conventional ICP optical spectra?
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What is the purpose of the differentially pumped interface in ICP-MS?
What is the purpose of the differentially pumped interface in ICP-MS?
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What is the application of CE-MS in the pharmaceutical industry?
What is the application of CE-MS in the pharmaceutical industry?
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What is the advantage of CE-MS in terms of speed?
What is the advantage of CE-MS in terms of speed?
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What is the function of the negative voltage in ICP-MS?
What is the function of the negative voltage in ICP-MS?
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What are the peaks in an ICP-MS spectrum used for?
What are the peaks in an ICP-MS spectrum used for?
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Study Notes
Electrospray Ionization (ESI) and Matrix Assisted Laser Desorption Ionization (MALDI)
- ESI and MALDI are two common ionization techniques used in CE/MS
- CE/MS provides high separation efficiency and molecular mass information in a single analysis
- Advantages of CE/MS include:
- High resolving power and sensitivity
- Requires minimal volume (nL)
- Analyzes at high speed
- Major application is biological studies for protein and peptide analysis
- Often used for routine analysis of pharmaceutical drugs
Inductively Coupled Plasma-Mass Spectrometry (ICP-MS)
Principle
- ICP torch serves as an atomizer and ionizer to produce positive metal ions
- Metal ions are sampled through a differentially pumped interface linked to a mass analyzer
- Spectra produced by ICP-MS are simpler and easier to interpret compared to conventional ICP optical spectra
- Resultant spectra consist of a simple series of isotope peaks for each element present
Instrumentation
- Positive ions are separated from electrons and molecular species by a negative voltage
- Then accelerated and focused by a magnetic ion lens onto the entrance orifice of a quadrupole mass analyzer
Performance Specifications
- Mass range of 3 to 300
- Ability to resolve ions differing in m/z by 1
- Dynamic range of six orders of magnitude
- Over 90% of elements in the periodic table have been determined by ICP-MS
- Measurement times of 10 s/element
- Detection limits in the range of 0.1 to 10 ppb for most elements
- Relative standard deviations of 2% to 4% for concentrations to the calibration curves
Spectroscopic Interferences
- Occur when an ionic species in the plasma has the same m/z values as an analyte ion
- Categories: Isobaric ions
- Isobaric ions: two elements with isotopes of essentially the same mass
- Examples: 40Ar+ and 40Ca+, 62Ni+, 63Cu+, 64Zn+, and 66Zn+
- Corrections can be carried out with appropriate software
- Some spectroscopic interferences can be reduced or eliminated by using high-resolution mass spectrometers
Matrix Effects
- Become noticeable at concomitant concentrations of > 500 to 1000 mg/mL
- Usually cause a reduction in the analyte signal
- Can be minimized by:
- Using more dilute solutions
- Altering the sample introduction procedure
- Separating out the offending species
- Using an internal standard
Applications
- ICP-MS is well suited to the rapid characterization and semiquantitative analysis of various types of naturally occurring and manufactured complex materials
- Easily adapted to multielement analyses
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Description
This quiz covers the principles and applications of ICP-MS, including its performance specifications, mass range, and detection limits. Test your knowledge of this analytical technique used in elemental analysis.
