an overview of lcms and gcms and its applications.... 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 INTERFACE Apart from being an inlet system for the MS, an LC–MS interface is also the coupling of a detector (MS) to a chromatograph. The choice of LC–MS interface strongly influences the characteristics of the MS as a detector for LC. Therefore, we should keep in mind what characteristics are ideal for an LC detector 1. Direct liquid introduction (DLI): The DLI interface was developed in order to solve the problems with in-capillary evaporation in the capillary inlet. In a DLI interface, the column effluent is nebulized by the disintegration into small droplets of a liquid jet formed at a small diaphragm After desolvation of the droplets in a desolvation chamber, the analytes can be analysed using solvent-mediated CI with the LC solvents as the reagent gas. Advantages: • No heat is applied to the interface and it is therefore able to deal with thermally labile materials better than the moving-belt interface. • The interface contains no moving parts and is cheap and simple to construct and operate and is inherently more reliable than the moving-belt interface. • Both positive- and negative-ion CI spectra can be generated and the interface provides molecular weight information, plus it can also be used for sensitive quantitative and semi-quantitative procedures. Disadvantages: • Involatile compounds are not usually ionized with good efficiency. • The pinhole is prone to blockage and therefore the system must be kept completely free of solid materials. • Only a small proportion of the flow from a conventional HPLC column is able to enter the source of the mass spectrometer and sensitivity is consequently low 2. Moving belt/wire: In a moving-belt interface (MBI), the column effluent is deposited onto an endless moving belt from which the solvent is evaporated by means of gentle heating and efficiently exhausting the solvent vapours. After removal of the solvents, the analyte molecules are (thermally) desorbed from the belt into the ion source and mass analysed. The MBI for LC.MS was used in a wide variety of applications, including the analysis of drugs and their metabolites, pesticides, steroids, alkaloids, polycyclic, aromatic hydrocarbons and others. Advantages: • The interface can be used with a wide range of HPLC conditions. • The analyst does have some choice of the ionization method to be used; EI, CI and FAB are available, subject to certain limitations, and thus both molecular weight and structural information may be obtained from the analyte(s) under investigation.

1. SUBMITTED BY
NIHAL. P
FIRST YEAR M.PHARM
NATIONAL COLLEGE OF PHARMACY
UNDER GUIDENCE OF
PROFF.KATHIRVEL
1

2. * 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
2

3. PARTS OF LC-MS
3

4. Apart from being an inlet system for the
MS, an LC–MS interface is also the coupling
of a detector (MS) to a chromatograph.
The choice of LC–MS interface strongly
influences the characteristics of the MS as
a detector for LC. Therefore, we should
keep in mind what characteristics are ideal
for an LC detector
4

5. 1. Direct liquid introduction (DLI):
- The DLI interface was developed in order to solve the problems with in-
capillary evaporation in the capillary inlet.
- In a DLI interface, the column effluent is nebulized by the disintegration
into small droplets of a liquid jet formed at a small diaphragm After
desolvation of the droplets in a desolvation chamber, the analytes can be
analysed using solvent-mediated CI with the LC solvents as the reagent
gas.
5

6. Advantages:
• No heat is applied to the interface and it is therefore able to deal with thermally
labile materials better than the moving-belt interface.
• The interface contains no moving parts and is cheap and simple to construct
and operate and is inherently more reliable than the moving-belt interface.
• Both positive- and negative-ion CI spectra can be generated and the interface
provides molecular weight information, plus it can also be used for sensitive
quantitative and semi-quantitative procedures.
Disadvantages:
• Involatile compounds are not usually ionized with good efficiency.
• The pinhole is prone to blockage and therefore the system must be kept
completely free of solid materials.
• Only a small proportion of the flow from a conventional HPLC column is able to
enter the source of the mass spectrometer and sensitivity is consequently low.
6

7. 2. Moving belt/wire:
• In a moving-belt interface (MBI), the column effluent is deposited onto an
endless moving belt from which the solvent is evaporated by means of gentle
heating and efficiently exhausting the solvent vapours. After removal of the
solvents, the analyte molecules are (thermally) desorbed from the belt into the
ion source and mass analysed.
• The MBI for LC.MS was used in a wide variety of applications, including the
analysis of drugs and their metabolites, pesticides, steroids, alkaloids,
polycyclic, aromatic hydrocarbons and others.
7

8. Advantages:
• The interface can be used with a wide range of HPLC conditions.
• The analyst does have some choice of the ionization method to be used; EI,
CI and FAB are available, subject to certain limitations, and thus both molecular
weight and structural information may be obtained from the analyte(s) under
investigation.
Disadvantages:
• An intense chemical background from the material from which the belt was
made is often observed in the mass spectra generated by this type of interface
unless adequate conditioning is carried out.
• The belt is prone to break during operation.
• Problems may be encountered in the analysis of thermally labile compounds,
as heat is required for mobile-phase removal and for the transfer of analyte
from the belt into the source of the mass spectrometer, and highly involatile
compounds which cannot be desorbed from the belt, unless FAB is used for
ionization.
8

9. 3. Thermospray (TSP):
They are of 2 type:
a) Real-TSP ionization
b) Discharge electrode for external ionization and repeller electrode
9

10. • In a thermospray (TSP) interface, a jet of vapour and small droplets is formed
out of a heated vaporizer tube into a low-pressure region. Nebulization takes
place as a result of the disruption of the liquid by the expanding vapour that is
formed upon evaporation of part of the liquid in the tube.
• Before the onset of the partial inside-tube evaporation a considerable amount
of heat is transferred to the solvent, which assists in the desolvation of the
droplets in the low pressure region. By applying efficient pumping directly at the
ion source up to 2 ml/min of aqueous solvents can be introduced into the MS
vacuum system. The ionization of the analytes takes place by means of ion-
molecule reactions and ion evaporation processes.
10

11. 4. Partical beam (PB):
• During the desolvation of the droplets, the less volatile analyte molecules
coagulate into small particles, typically 50-300nm. The solvent vapour and
nebulization gas are separated from the particles by means of molecular-beam
technology.
• The mixture is expanded at a nozzle into a vacuum chamber. The low mass
solvent molecules show a greater tendency to diffuse away from the centre of
the expansion, while the heavier analyte particles are kept in the core of the
vapour jet. The core of the jet is then sampled by a skimmer.
• The region between the first set of orifices is maintained at between 2 and 10
torr, and that between the second set between 0.1 and 1 torr. In the momentum
separator, sufficient pressure reduction is achieved to generate EI and solvent-
independent CI mass spectra.
11

12. 5. Atmospheric pressure chemical ionization (APCI)
• Here, the HPLC effluent is passed through a pneumatic nebulizer where the
droplets are both generated and desolvated. The spray so formed then passes
through a heated region where the vapour is dried.
• The neutral species thus produced are then passed through a corona discharge –
the latter occurs when the field at the tip of the electrode is sufficiently high to ionize
the gas surrounding it but insufficiently high to cause spark – where ionization of
the analyte is effected by CI-type processes with the vaporized solvent acting as
the reagent gas.
• The technique is capable of dealing with flow rates between 0.5 - 2 ml/min, so
making it directly compatible with 4.6 mm columns, and is much more tolerant to a
range of buffers. 12

13. 6. Conti. Flow fast atom bombardment (cf-FAB)
• In a continuous-flow fast-atom bombardment (Cf-FAB) interface, typically a
5-15 µl/min liquid stream, mixed with 5% glycerol (or) thioglycerol (or)
nitrobenzyl alcohol as FAB matrix, flows through a narrow-bore fused-silica
capillary towards either a stainless-steel frit or a (goldplated) FAB target. At the
target or frit, a uniform liquid film is formed due to a subtle balance between
solvent evaporation and solvent delivery. Ions are generated by bombardment
of the liquid film by fast atoms or ions, common to FAB.
• The fast atom like Ar or Xe is used for bombarding the sample and ions are
sputtered out of the solution and enters into MS.
13

14.  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. 14

15. 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.
15

16.  The sample solution is injected into the GC inlet where it
is vaporized and swept onto a chromatographic column
by the carrier gas (usually helium).
 The sample flows through the column and the
compounds comprising the mixture of interest are
separated by interaction with the coating of the column
(stationary phase) and the carrier gas (mobile phase).
 The latter part of the column passes through a heated
transfer line and ends at the entrance to ion source where
compounds eluting from the column are converted to
ions.
PRINCIPLE OF GC-MS
16

17.  The GC-MS is composed of two major building blocks:
the gas chromatograph and the mass spectrometer.
 Carrier Gas, N2 or He, 1-2 mL/min
 Injector
 Oven
 Column
 Detector
17

18. 18

19.  Two capillary tubes aligned with a small space between them.
(1 mm)
 A vacuum is created between the two tubes using a rotary
pump.
 The GC effluent enters the vacuum region, those molecules
which continue in the same direction enter the second capillary
tube and continue to the ion source.
19

20.  The carrier gas molecules are more easily diverted from the
linear path by collisions.
 The analyte molecules are much larger and carry more
momentum.
 The surface of the separator must be inactive and a reasonably
even temperature.
20

21. Jet Separator
21

22. Environmental Monitoring and Cleanup
GC-MS is becoming the tool of choice for tracking
organic pollutants in the environment.
GC-MS can analyze the particles from a human body in
order to help link a criminal to a crime. The analysis of
fire debris using GC-MS is well established, and there
is even an established American Society for Testing
Materials (ASTM) standard for fire debris analysis.
Criminal forensic
22

23. 1) PHARMACEUTICAL CHEMISTRY 4TH EDITION ,EDITED BY AH BECKETT
AND JB STENLAKE.
2) GAS CHROMATOGRAPHY-MASS SPECTROSCOPY FROM WIKIPEDIA ,
THE FREE ENCYCLOPEDIA.
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