Mass spectrometry is a technique that measures the mass-to-charge ratio of ions. It works by ionizing analyte molecules, then separating the ions based on their m/z ratios using electric and magnetic fields. The data produced are mass spectra, which provide information about molecular structure. Key developments included techniques like electron ionization, electrospray ionization, and matrix-assisted laser desorption/ionization, which allowed analysis of nonvolatile and thermally labile compounds. Mass spectrometry determines isotopic composition and is used to study elemental, molecular, and isotopic properties of substances.

2. Weight
The most common definition of weight found in
introductory physics textbooks defines weight as
the force exerted on a body by gravity.
An object's weight depends on its mass and the
strength of the gravitational pull.
The force with which an object near the Earth or
another celestial body is attracted toward the
center of the body by gravity.

3. Mass
• Mass is both a property of a physical body and
a measure of its resistance to acceleration (a
change in its state of motion) when a net force
is applied. An object's mass also determines
the strength of its gravitational attraction to
other bodies. The basic SI unit of mass is the
kilogram (kg).

8. • Mass spectrometry is a microanalytical
technique that can be used selectively to
detect and determine the amount of a given
analyte.
• Mass spectrometry is also used to determine
the elemental composition and some aspects
of the molecular structure of an analyte.
• The tools of mass spectrometry are mass
spectrometers, and the data are mass spectra.

9. • The experimental measurement of the mass
of gas-phase ions produced from molecules of
an analyte.
• Mass spectrometry concerns itself with the
mass of the isotopes of the elements, not the
atomic mass of the elements.

10. Atomic number

11. Atomic number
The atomic number or proton
number (symbol Z) of a chemical element is the
number of protons found in the nucleus of
every atom of that element. The atomic number
uniquely identifies a chemical element. It is
identical to the charge number of the nucleus. In
an uncharged atom, the atomic number is also
equal to the number of electrons.

14. Atomic mass
• The atomic mass of an element is the
weighted average of the naturally occurring
stable isotopes that comprise the element.

15. Ionization
• Ionization or ionisation, is the process by
which an atom or a molecule acquires a
negative or positive charge by gaining or
losing electrons, often in conjunction with
other chemical changes.

19. • Mass spectrometry does not directly
determine mass; it determines the mass-to-
charge ratio (m/z) of ions.
• It is a fundamental requirement of mass
spectrometry that the ions be in the gas phase
before they can be separated according to
their individual m/z values and detected.

20. Before 1970- ionization techniques
• Analytes having significant vapor pressure
were amenable to mass spectrometry because
gas-phase ions could only be produced from
gas-phase molecules by the techniques of
electron ionization (EI) or chemical ionization
(CI).
• Nonvolatile and thermally labile molecules
were not amenable.

21. After 1970- Desorption techniques
• After 1970, the capabilities of mass spectrometry
were expanded by the development of
desorption/ionization (D/I)techniques, the
generic process of generating gas-phase ions
directly from a sample in the condensed phase.
• The first viable and widely accepted technique2
for D/I was fast atom bombardment (FAB), which
required nanomoles of analyte to produce an
interpretable mass spectrum.

22. In 1980
• During the 1980s, electrospray ionization (ESI)
and matrix-assisted laser
desorption/ionization (MALDI) eclipsed FAB, in
part because they required only picomoles of
analyte for analysis.
• ESI and MALDI are suitable for analysis of
femtomole quantities of thermally labile and
nonvolatile analytes

23. The Concept of Mass Spectrometry
• Ions are charged particles and, as such, their
position in space can be manipulated with the
use of electric and magnetic fields.
• When only individual ions are present, they can
be grouped according to their unique properties
(mass and the number of charges) and moved
from one point to another.
• In order to have individual ions free from any
other forms of matter, it is necessary to analyze
them in a vacuum.

24. • Mass spectrometry takes advantage of ions in
the gas phase at low pressures to separate
and detect them according to their
• mass-to-charge ratio (m/z) – the
mass of the ion on the atomic scale
divided by the number of charges
that the ion possesses.

25. • Only ions are detected in mass spectrometry.
• Any particles that are not ionic (molecules or
radicals ) are removed from the mass
spectrometer by the continuous pumping that
maintains the vacuum.
• Both molecules and radicals are particles that
have no charge.
• Molecules are characterized by an even number
of electrons .
• Radicals by an odd number of electrons.

26. • The mass component that makes up the dimensionless
m/z unit is based on an atomic scale rather than the
physical scale.
• Mass physical scale is defined as one kilogram being
the mass of one liter of water at a specific temperature
and pressure.
• The atomic mass scale is defined based on a fraction of
a specific isotope of carbon;
• i.e., 1 mass unit on an atomic scale is equal to 1/12 the
mass of the most abundant naturally occurring stable
isotope of carbon, 12C. This definition of mass.
• Mass is represented by the symbol u, which is
synonymous with dalton(Da).

27. • In the study of mass spectrometry, it is
important to always keep in mind that the
entity measured in the mass spectrometer is
the mass-to-charge ratio of an ion, not the
mass of the ion.
• It is inappropriate to use a unit of mass when
describing the mass-to-charge ratio of an ion.
Ions have both mass and an m/z value.

28. M+ ions
• The most common ionization process for gas-
phase analysis,
• EI, transfers energy to the neutral molecule (a
species characterized as having an even number
of electrons) in the vapor state, giving it sufficient
energy to eject one of its own electrons, thereby
leaving a residual positive charge on the now
ionic species. This process produces a molecular
ion with a positive charge and odd number of
electrons, as represented by the M+

29. • This M + may have considerable excess energy that can be
dissipated through fragmentation of certain chemical bonds.
• Cleavage of various chemical bonds leads to the production of
positive-charge fragment ions whose mass is equal to the sum of
the atomic masses of the constituent atoms.
• Not all of the molecular ions necessarily decompose into fragment
ions. For compounds producing a relatively stable M +, such as
those stabilized through resonance, like aromatic compounds, an
intense molecular-ion peak will be recorded because the M+ tends
to survive or resist fragmentation.
• For compounds that do not produce stable molecular ions, like
aliphatic alcohols, nearly all of them decompose into fragment ions.
In these cases, the mass spectrum contains only a small peak
representing the M+ Various combinations of the above-described
processes are the basis of the chemical “fingerprint” in the form of
a mass spectrum for a given compound.

30. Calutron mass spectrometers were used in the Manhattan
Project for uranium enrichment.

31. Replica of J.J. Thomson's third mass
spectrometer

32. Surface ionization source at
the Argonne National
Laboratory linear accelerator

34. ISOTOPES

35. • An element is specified by the number of
protons in its nucleus. This equals the atomic
number of the respective element, and thus
determines its place within the periodic table
of the elements. The atomic number is given
as a subscript preceding the elemental
symbol, e.g., 6C in case of carbon.

36. • Atoms with nuclei of the same atomic number
differing in the number of neutrons are
termed isotopes.
• The mass number of an isotope is given as
superscript preceding the elemental symbol,
e.g., 12C.

37. Monoisotopic elements
Elements do exist in only one naturally occurring
stable isotope.
• Fluorine (19F),
• Sodium (23Na),
• Phosphorus (31P)
• Iodine (127I)
• The monoisotopic elements are also referred
to as A or X elements

38. Di-isotopic Elements
• Several elements naturally exist in two
isotopes.
• The first group has been termed A+1 or X+1
elements, the latter ones have been termed
A+2 or X+2 elements.

39. X+1 Elements
• Hydrogen (1H, 2H = D), carbon (12C, 13C) and
nitrogen (14N, 15N).
• Deuterium (D) is of low abundance (0.0115
%)
• And therefore, hydrogen is usually treated as
monoisotopic or X element

40. X+2 Elements
• Chlorine (35cl, 37cl)
• Bromine (79br, 81br) are Commonly Known,
• Copper (63cu, 65cu),
• Gallium (69ga, 71ga),
• Silver (107ag, 109ag),
• Indium (113in, 115in) and
• Antimony (121Sb, 123Sb)

41. X-1 element
The elements lithium (6Li, 7Li), boron (10B, 11B)
and vanadium (50V, 51V) come together with a
lighter isotope of lower abundance than the
heavier one and thus, they can be grouped
together as X–1 elements.

42. Polyisotopic Elements
The majority of elements belongs to the
polyisotopic elements because they consist of
three or more isotopes showing a wide variety
of isotopic distributions.

43. The isotopic mass
• It is the exact mass of an isotope.
• It is very close to but not equal to the nominal
mass of the isotope .
• The only exception is the carbon isotope 12C
which has an isotopic mass of 12.000000 u.

44. Monoisotopic Mass
The exact mass of the most abundant isotope of
an element is termed monoisotopic mass.