LC-MS combines liquid chromatography with mass spectrometry. It involves removing the detector from the LC column and interfacing the column directly with the mass spectrometer. The two key components are the ion source, which generates ions, and the mass analyzer, which sorts the ions. Common ion sources used include electrospray ionization, atmospheric pressure chemical ionization, and atmospheric pressure photoionization. Popular mass analyzers are quadrupole, time-of-flight, ion trap, and Fourier transform ion cyclotron resonance. LC-MS has applications in fields like molecular weight determination, structural determination, pharmaceutical analysis, food safety testing, and environmental analysis.

1. LIQUID CHROMATOGRAPHY –
MASS SPECTROSCOPY (LC-MS)
Presented by
Md Akbar Siddiq Khan
M.Pharm
Nizam College Of Pharmacy
Hyderabad - A.P

2. What is LC-MS?
• It is the combination of liquid chromatography
and the mass spectrometry.
• In LC-MS we are removing the detector from the
column of LC and fitting the column to interface
of MS.
• In the most of the cases the interface used in LC-
MS are ionization source.

3. PROBLEMS IN COMBINING
HPLC AND MS
HPLC MS
• Liquid phase operation Vacuum operation
• 25 - 50 deg. C 200 - 300 deg. C
• No mass range Up to 4000 Da for
quadrupole MS
limitations
Requires volatile buffers
• Inorganic buffers Accepts 10 ml/min gas
• 1 ml/min eluent flow is flow
equivalent to 500
ml/min of gas

4. PARTS OF LC-MS
Two key components in this process are the
ion source, which generates the ions, and the
mass analyzer, which sorts the ions.
Several different types of ion sources are
commonly
used for LC/MS.

7. MOBILE PHASE:-
The mobile phase is the solvent that moves the
solute through out column.
 General requirements:-
(1)low cost, uv transperancy,high purity.
(2)low viscosity, low toxicity, non flammability.
(3)non corrosive to LC system component.
 Solvent strength and selectivity:-
it is the ability of solvent to elute solutes from a
column.

8. COLUMN:-
 Column type:-
 Specialized mode:-
 The use of di-functional or tri-functional silanes to create
bonded groups with two or three attachement points
leading to phases with higher stability in low or higher pH
and lower bleed for LCMS
 Most widely used columns for LCMS are:-
(1) fast LC column.
the use of short column. (15-50mm)
(2) Micro LC column.
the use of large column. ( 20-150mm)

9. Sample preparation:-
 Sample preparation generally consists of concentrating
the analyte and removing compounds that can cause
background ion or suppress ionization.
 Example of sample preparation include:-
(1) on –column concentration to increase analyte
concentration.
(2) desalting to reduce the sodium and potassium
adduct formation that commonly occurs in electro
spray.
(3) filtration to separate a low molecular-weight drug
from proteins in plasma, milk, or tissue.

10. Ionization and Interface:-
• It is difficult to interface a liquid chromatography
to a mass-spectrometer cause of the necessity
to remove the solvent.
• The commnly used interface are:-
(1) Electrospray ionization (ESI)
(2) Thermospray ionization (TSI)
(3) Atmospheric pressure chemical ionization
(APCI)
(4) Atmospheric pressure photoionization(APPI)
(5) Partical beam ionization.

11. Electron spray ionization.
Generate analyte ions in solution before
the analyte reaches the mass
spectrometer.
The LC eluent is sprayed (nebulized) into
a chamber at atmospheric pressure in the
presence of a strong electrostatic field and
heated drying gas.
The electrostatic field causes further
dissociation of the analyte molecules.
The heated drying gas causes the solvent
in the droplets to evaporate. As the droplets
shrink, the charge concentration in the
droplets increases.
Eventually, the repulsive force between
ions with like charges exceeds the
cohesive forces and ions are ejected
(desorbed) into the gas phase.
These ions are attracted to and pass
through a capillary sampling orifice into the
mass analyzer.

12. Atmospheric pressure chemical ionization
(APCI)
In APCI, the LC eluent is sprayed
through a heated (typically 250 C –
400 C) vaporizer at atmospheric
pressure.
The heat vaporizes the liquid. The
resulting gas-phase solvent
molecules are ionized by electrons
discharged
from a corona needle.
The solvent ions then transfer
charge to the analyte molecules
through chemical reactions
(chemical ionization).
The analyte ions pass through a
capillary sampling orifice into the
mass analyzer.

13. Atmospheric pressure photoionization(APPI)
Atmospheric pressure
photoionization (APPI)for LC/MS is a
relatively new technique.
 As in APCI, a vaporizer converts
the LC eluent to the gas phase. A
discharge lamp generates photons in
a narrow range of ionization energies.
 The range of energies is carefully
chosen to ionize as many analyte
molecules as possible while
minimizing the ionization of solvent
molecules.
The resulting ions passthrough a
capillary sampling orifice into the
mass analyzer.

14. Particle beam ionization.

15. Mass Analyser:-
• They deflects ions down a curved tubes in a
magnetic fields based on their kinetic energy
determined by the mass, charge and velocity.
• The magnetic field is scanned to measure
different ions.
 Types of mass analyzer:-
(1) Quadrapole mass filter.
(2) time of flight
(3) Ion trap
(4) Fourier transform ion cyclotron resonance
(FT-ICR or FT-MS)

16. Quadrapole mass filters
 A quadrupole mass analyzer consists of four parallel
rods arranged in a square. The analyte ions are
directed down the center of the square.
 Voltages applied to the rods generate electromagnetic
fields. These fields determine which mass-to-charge
ratio of ions can pass through the filter at a given time.
Quadrupoles tend to be the simplest and least
expensive mass analyzers.
 Quadrupole mass analyzers can operate in two
modes:
• Scanning (scan) mode
• Selected ion monitoring (SIM) mode
In scan mode, the mass analyzer monitors a range of mass-to-charge ratios.
In SIM mode, the mass analyzer monitors only a few massto-charge ratios. SIM
mode is significantly more sensitive than scan mode but provides information about
fewer ions. Scan mode is typically used for qualitative analyses or for quantitation
when all analyte masses are not known in advance.SIM mode is used for quantitation
and monitoring of target compounds.

17. time of flight
In a time-of-flight (TOF) mass
analyzer, a uniform
electromagnetic force is applied to
all ions at the same time, causing
them to accelerate down a flight
tube.
Lighter ions travel faster and
arrive at the detector first, so the
mass-to-charge ratios of the ions
are determined by their arrival
times.
Time-offlight mass analyzers
have a wide mass range and can
be very accurate in their mass
measurements.

18. Ion trap
An ion trap mass analyzer consists of a circular ring electrode plus two
end caps that together form a chamber. Ions entering the chamber are
“trapped” there by electromagnetic fields. Another field can be applied to
selectively eject ions from the trap.
Ion traps have the advantage of being able to perform multiple stages of
mass spectrometry without additional mass analyzers.

19. Fourier transform ion cyclotron resonance (FT-ICR
or FT-MS)
An FT-ICR mass analyzer (also called FT-MS) is another type of trapping analyzer.
Ions entering a chamber are trapped in circular orbits by powerful electrical and
magnetic fields.
When excited by a radio-frequency (RF) electrical field, the ions generate a
timedependent current.
This current is converted by Fourier transform into orbital frequencies of the ions which
correspond to their mass-tocharge ratios.

22.  Molecular weight determination
 Determining the molecular weight of green fluorescent
proteins
 Structural determination e.g. structural determination of
ginsenoside.
 Pharmaceutical application e.g. identification of bile acids
metabolites.
 Biochemical application e.g. rapid protein identification
using capillary lc/ms/ms.
 Food application e.g. identification of aflatoxin in food
determination of vitamin D3 in poultry feed supplement
using MS3
 Environmental application e.g. detection of phenyl urea
herbicides, detection of low level of carbaryl in food.

23. Referance:-
• Wikimedia Foundation. 2010.
(1) W. Paul & H. Steinwedel; Zeitschrift für
Naturforschung, 8A; 1953, p448.
(2) W. Paul; Agewandte Chemie -
International Edition, 29; 1990, p739.
(3) G. C. Stafford et al.; International
Journal of Mass Spectrometry and Ion
Processes, 60; 1984, p85 and Analytical
Chemistry, 59; 1987, p1677.