mass spectrometry equipment ideas

1. Inductively Coupled Plasma
Mass Spectrometry ((ICP-MS)

2. Mass Spectrometry
• Mass spectrometry (MS) is similar to NMR in that it has historically been of great value in
structure elucidation of relatively small organic & biomolecules.
• MS analysis of proteins & other biopolymers was initially hindered because analytes are
usually measured in the gas phase.
• The development of new methods now makes it possible to study large molecules i.e.
sample preparation (ionization)
multiquadrupole analysis
tandem MS instruments
powerful computers

3. Ionization and Analysis of Proteins
• Mass spectrometer generally consists of three components (figure 7.17).
ionization device
mass analyzer
ion detector
• Neutral molecules are ionized, & their positively charged ion products are directed through an
electric and/or magnetic field, and separated on the basis of mass-to-charge ratio (m/z).
• A detector then records the ions after separation.
• The “spectrum” generated by MS displays ion intensity as a function of m/z.

8. multiquadrupole
analysis

11. Continue……..
• Ionization of small organic & biological molecules is done by electron impact while
nonvolatile & biological macromolecules requires special treatment.
• In the late 1980s, “soft ionization” method was introduced for the macromolecules.
• Electrospray ionization (ESI) involve spray of sample’s solution via a metal needle or
capillary tip held at a potential (+ 5000 V) that results in tiny droplets (+ve ions)
• Solvent evaporates, and ions are directed into the analyzer for separation.
• Pulses from N2 laser used to ionize proteins from surface (soft laser desorption; SLD)
• Both ESI & SLD are liquid-phase processes hence require purified samples

12. Electrospray ionization (ESI)

13. • Laser desorption has been modified to a solid phase method, matrix-assisted laser
desorption ionization (MALDI), widely used technique for protein analysis.
• In MALDI, sample is placed in matrix of small organic molecules & irradiated by laser pulse.
• Matrices absorb laser energy, causing ionization of macromolecular sample.
• Several types of mass analyzers are used for ion separation, including time-of-flight (TOF),
quadrupoles, and ion traps.
• The TOF-MS is most widely used technique in which each ion produced has same initial
kinetic energy, but speed varies with mass.
• Mass is determined by measurement of an ion’s time-of-flight to detector.
Continue……..

14. time-of-flight (TOF)

15. MS Applications in Biochemistry
• MS, becoming a standard tool in the analysis of biological molecules and biological
processes i.e.
• Identification of peptides & proteins
Identification of proteins is widely done by MS.
important ions resulting from the removal of an electron by ionization procedures are
+ ve charged molecular ions (m+) or protonated molecular ions (m+nh)n-1.
measurement of molecular mass provides the molecular weight of original molecule.
the accuracy of this method for molecular weight determination is about 0.01%.

16. some molecular ions are unstable & disintegrate to produce fragment ions.
these fragmentation processes are useful in structural elucidation of smaller molecules.
• One MS method for peptide identification is called peptide mass fingerprinting.
unknown sample is digested with trypsin to produce fragments & analyzed by MALDI-MS.
resulting spectrum displays the masses of peptide fragments.
used as a “fingerprint” of sample & compared with known fragmented patterns in a
sequence database.
Continue……..

17. • Characterization of post-translational modification processes
after translation, proteins are often modified by covalent attachment of specific functional
groups like
Phosphorylation
Glycosylation
these chemical modifications can easily be detected by MS
Continue……..

18. • Peptide Sequencing
small peptides & proteins may be sequenced by MS procedures.
the peptide sample is ionized & fragmented at the peptide bonds by collision-induced
dissociation.
size analysis of the series of fragments produced leads to the sequence of amino acids.
Continue……..

19. • Protein-protein interactions
most important goal of proteomics is to study how proteins interact with each other.
ESI-MS and MALDI-TOF are currently being used to investigate how proteins associate
to form biologically active multi subunit complexes.
Continue……..

20. ICP-MS
• The inductively coupled plasma (ICP) & the quadrupole mass analyzer caused an increase
in the use of atomic MS as an analytical tool.
• ICP-MS permits determination of most of elements at very-low-concentration levels.
• It has great advantages over other techniques for elemental analysis as it used to
determine most elements at high sensitivity & at a wide range of concentrations.
• Moreover, isotope ratios can be obtained, providing geochemical & geochronological
information.

21. • There are several properties of MS as an analyzer & the argon ICP as an ionization
source make ICP-MS an attractive combination.
• The ICP has a high ionization efficiency & it produces mainly singly charged +ve ions.
• Hence, mass spectra are very simple & elements are easily identified and the isotope
ratios can be easily measured.
• Moreover, the mass spectrometer is very sensitive, with detection limits up to three
orders of magnitude better than ICP-OES.
• And is linear over a wide dynamic range of up to five orders of magnitude.
• Table 10.21 presents some aspects of ICP-OES & MS that complement each other.
Continue……..

23. • The instrument is an ICP interfaced with a quadrupole MS as shown in figure 10.36a.
• This ICP source is horizontal, with argon plasma concentric to the mass spectrometer
inlet.
• Figure 10.36b shows the layout of a new ICP-MS, the Perkinelmer nexion 300, with the
plasma vertical to the mass spectrometer.
• This instrument has a quadrupole ion deflector (QID) above the torch.
• The QID turns positively charged ions from the plasma 90° to the left, into the mass
analyzer, while nonionized material flows straight up & out of the system.
Instrumentation

25. • While the instrument has a QID & a quadrupole reaction cell, it has only one analyzing
quadrupole
• ICPS operate at atmospheric pressure & at a temperature of about 10,000 k.
• While, the MS requires a high vacuum (10−4–10−6 torr) & operates at room
temperature.
• Most ICP-MS systems have an interface similar to the one shown in figure 10.37, but the
nexion 300 shown in figure 10.36b has three cones.
• In figure 10.37, the argon ICP plasma is on the right side of the diagram.
• Ions from the plasma enter into mass spectrometer through a two-stage interface.
Continue……..

27. • Plasma is centered on sampler cone, & ions & plasma gas pass through the orifice in
the cone into a vacuum-pumped region.
• Most of argon gas is pumped away in this region.
• The remaining ions pass through the skimmer cone into the mass spectrometer.
• The design of this cone restricts the flow of ions into the mass spectrometer to the
central part of the flow initially coming from plasma.
• Region behind the skimmer cone is evacuated to a pressure of about 10−4 torr by a
turbomolecular pump.
• This region can be isolated from the higher pressure of the interface region by a gate
valve
Continue……..

28. • This permits the sampler & skimmer cones to be removed for cleaning without breaking
the vacuum in mass spectrometer.
• Both sampler & skimmer cones are made of either nickel or platinum & are water cooled
by contact with water flowing within the interface chamber.
• The hyper skimmer cone in the perkinelmer instrument is designed to focus the ions
even more tightly, with the aim of increasing stability & eliminating drift.
• Series of ion-focusing elements similar to those developed for double-focusing mass
spectrometers have been utilized to introduce the ions into the quadrupole.
Continue……..

29. • Interference effects due to the presence of large numbers of photons reaching detector
are eliminated by photon stops in older designs or off-axis ion lenses in newer one
• Background signals have been largely eliminated in modern ICP-MS instruments.
• Other mass analyzers are used with ICP ionization source, including high-resolution
magnetic sectors & TOFS.
• ICP-TOF mass analyzer systems as well as other designs have advantage of
simultaneous measurement of ions.
• Simultaneous measurement is critical for accurate determination of isotope abundances
as well as for accurate quantitative work using isotope dilution.
Continue……..

30. Applications of Atomic MS
• ICP-MS is particularly useful for rapid multi element determination of metals &
nonmetals at concentrations of ppq, ppt, and ppb.
• Only unit mass (low) resolution is required to discriminate between different elements,
as isotopes of different elements differ by 1 unit mass.
• There are only a few isotopic overlaps between elements, so one can usually find an
isotope to measure for any given element.
• The applications discussed are from many forms of atomic MS, including ICP-MS,
GDMS, and coupled chromatography-ICP-MS.

31. • Uses for ICP-MS include analysis of
environmental samples for ppb levels of trace metals & nonmetals.
body fluids for elemental toxins such as lead & arsenic
trace elements in geological samples, metals & alloys, & isotope ratios
Analysis of ceramics, semiconductors, pharmaceutical, forensic & cosmetic samples
Determination of platinum group catalysts in polymers, elemental analysis in petroleum
& chemical industries
Metal determinations in clinical chemistry & food chemistry.
Applications of ICP-MS

32. • Most common samples analyzed by ICP-MS are aqueous solutions.
• Sample is dissolved in acid, digested or fused in molten salt, & then diluted to desired
volume with water.
• All reagents must be of extremely high purity, given the sensitivity of the ICP-MS
• Aqueous solution is introduced into plasma using a peristaltic pump, nebulizer, & spray
chamber system.
• Solid samples can be analyzed by laser ablation ICP-MS or by coupling an electrothermal
vaporization (ETV) or electrothermal atomizer (ETA) to the ICP-MS.
Analysis of Sample

33. • Solids can also be analyzed by GDMS and spark source MS.
• Laser ablation ICP-MS can measure elements in fluid inclusions in rocks, microscopic
features in heterogeneous materials, & individual crystals in samples like granite.
• It can be used for analysis of artworks & jewelry.
• Quantitative analysis by ICP-MS is usually done with external calibration standards &
the addition of internal standards to all standards & samples.
• For determination of large number of elements, it is usual to add Li, Y, In, Tb, and Bi &
measure the ions 6Li, 89Y, 115In, 159Tb, and 209Bi as internal standards.
Continue……..

34. • Internal standard that is most closely matched in first ionization potential to the analyte is
generally used.
• Results obtained using this approach are generally very accurate & precise.
• Table 10.23 presents typical spike recovery & precision data for ICP-MS determination
of 25 elements in a certified reference material (crm) “trace elements in drinking water”
from high-purity standards, Charleston, SC
Continue……..

36. Recommended book
Biochemistry Laboratory: Modern Theory and Techniques
Rodney Boyer (Hope College)
Second Edition
Chapter 7: Spectroscopic Analysis of Biomolecules (D.
Mass Spectrometry)
Undergraduate Instrumental Analysis
James W. Robinson (7th Edition)
Chapter 10: Mass Spectrometry II: Spectral Interpretation and
Applications (10.4.1 ICP-MS)