8 gas chromatography jntu pharmacy

1
Gas Chromatography
BY
Dr. Suman Pattanayak
Associate Professor
Department of Pharma Analysis & QA.
Vijaya Institute of Pharmaceutical Sciences for Women
IV B. Pharm/ I Sem
Pharmaceutical Analysis

2
Gas chromatography is a technique used for
separation of volatile substances, or substances that
can be made volatile, from one another in a gaseous
mixture at high temperatures. A sample containing
the materials to be separated is injected into the gas
chromatograph. A mobile phase (carrier gas) moves
through a column that contains a wall coated or
granular solid coated stationary phase. As the
carrier gas flows through the column, the
components of the sample come in contact with the
stationary phase. The different components of the
sample have different affinities for the stationary
phase, which results in differential migration of
solutes, thus leading to separation

3
Martin and James introduced this separation
technique in 1952, which is the latest of the
major chromatograhpic techniques.
However, by 1965 over 18000 publications in
gas chromatography (GC) were available in
the literature. This is because optimized
instrumentation was feasible. Gas
chromatography is good only for volatile
compounds or those, which can be made
volatile by suitable derivatization methods or
pyrolysis. Thus, about 20% of chemicals
available can be analyzed directly by GC.

4
Gas chromatography can be used for both
qualitative and quantitative analysis.
Comparison of retention times can be used
to identify materials in the sample by
comparing retention times of peaks in a
sample to retention times for standards. The
same limitations for qualitative analysis
discussed in Chapter 26 also apply for
separations in GC. Quantitative analysis is
accomplished by measurement of either peak
height or peak area

5
Gas - Solid Chromatography
(GSC)
The stationary phase, in this case, is a solid
like silica or alumina. It is the affinity of
solutes towards adsorption onto the
stationary phase which determines, in part,
the retention time. The mobile phase is, of
course, a suitable carrier gas. This gas
chromatographic technique is most useful
for the separation and analysis of gases like
CH4, CO2, CO, ... etc. The use of GSC in
practice is considered marginal when
compared to gas liquid chromatography.

6
Gas - Liquid Chromatography
(GLC)
The stationary phase is a liquid with very
low volatility while the mobile phase is
a suitable carrier gas. GLC is the most
widely used technique for separation of
volatile species. The presence of a
wide variety of stationary phases with
contrasting selectivities and easy
column preparation add to the assets
of GLC or simply GC.

7
Instrumentation
It may be wise to introduce instrumental
components before proceeding further in
theoretical background. This will help clarify
many points, which may, otherwise, seem
vague. It should also be noted that a detector
will require special gas cylinders depending
on the detector type utilized. The column
temperature controller is simply an oven, the
temperature of which can be varied or
programmed

8
Syringe
Injector
Detector
Carrier Gas
Cylinder
Column
To Waste or Flow
Meter
Flow Controller
Two-Stage
Regulator

10
Three temperature zones can be identified:
1. Injector temperature, TI, where TI should allow flash
vaporization of all sample components.
2. Column temperature, Tc, which is adjusted as the
average boiling points of sample components.
3. Detector Temperature, TD, which should exclude
any possible condensation inside the detector.
Generally, an intuitive equation can be used to adjust
all three zones depending on the average boiling
point of the sample components. This equation is
formulated as:
TI = TD = Tc + 50 o
C

11
The Carrier Gas
Unlike liquid chromatography where
wide varieties of mobile phase
compositions are possible, mobile
phases in gas chromatography are very
limited. Only slight changes between
carrier gases can be identified which
places real limitations to
chromatographic enhancement by
change or modification of carrier gases

12
A carrier gas should have the following properties:
1. Highly pure (> 99.9%)
2. Inert so that no reaction with stationary phase or
instrumental components can take place,
especially at high temperatures.
3. A higher density (larger viscosity) carrier gas is
preferred.
4. Compatible with the detector since some detectors
require the use of a specific carrier gas.
5. A cheap and available carrier gas is an advantage.

13
Longitudinal Diffusion Term
This is an important factor contributing to band
broadening which is a function of the
diffusivity of the solute in the gaseous
mobile phase as well as the molecular
diffusion of the carrier gas itself.
HL = K DM /V
Where; DM is the diffusion coefficient of solute
in the carrier gas. This term can be
minimized when mobile phases of low
diffusion, i.e. high density, are used in
conjunction with higher flow rates.

14
The same van Deemter equation as in LC
can be written for GC where:
H = A + B/V + CV
The optimum carrier gas velocity is given
by the derivative of van Deemter
equation
Vopt = { B/C }1/2
However, the obtained velocity is much
greater than that obtained in LC.

15
The carrier gas pressure ranges from 10-50 psi.
Higher pressures potentially increase
compression possibility while very low
pressures result in large band broadening
due to diffusion. Depending on the column
dimensions, flow rates from 1-150 mL/min
are reported. Conventional analytical
columns (1/8”) usually use flow rates in the
range from 20-50 mL/min while capillary
columns use flow rates from 1-5 mL/min
depending on the dimensions and nature of
column. In most cases, a selection between
helium and nitrogen is made as these two
gases are the most versatile and common
carrier gases in GC.

16
Gas Chromatography
Lecture 37

17
Injectors
Septum type injectors are the most common. These are
composed of a glass tube where vaporization of the
sample takes place. The sample is introduced into
the injector through a self-sealing silicone rubber
septum. The carrier gas flows through the injector
carrying vaporized solutes. The temperature of the
injector should be adjusted so that flash
vaporization of all solutes occurs. If the temperature
of the injector is not high enough (at least 50
degrees above highest boiling component), band
broadening will take place.

18
Carrier
Gas
Syringe
Vaporization
Chamber
To
Column
Septum

26
Column Configurations and
Ovens
The column in chromatography is undoubtedly
the heart of the technique. A column can
either be a packed or open tubular.
Traditionally, packed columns were most
common but fast developments in open
tubular techniques and reported advantages
in terms of efficiency and speed may make
open tubular columns the best choice in the
near future. Packed columns are relatively
short (~2meters) while open tubular columns
may be as long as 30-100 meters

27
Packed columns are made of stainless steel or
glass while open tubular columns are usually
made of fused silica. The temperature of the
column is adjusted so that it is close to the
average boiling point of the sample mixture.
However, temperature programming is used
very often to achieve better separations. The
temperature of the column is assumed to be
the same as the oven which houses the
column. The oven temperature should be
stable and easily changed in order to obtain
reproducible results.

28
Detection Systems
Several detectors are
available for use in
GC. Each detector
has its own
characteristics and
features as well as
drawbacks.
Properties of an
ideal detector
include:
1. High sensitivity
2. Minimum drift
3. Wide dynamic range
4. Operational temperatures
up to 400 o
C.
5. Fast response time
6. Same response factor for
all solutes
7. Good reliability (no fooling)
8. Nondestructive
9. Responds to all solutes
(universal)

29
a. Thermal Conductivity Detector
(TCD)
This is a nondestructive detector which is used for the
separation and collection of solutes to further
perform some other experiments on each purely
separated component. The heart of the detector is a
heated filament which is cooled by helium carrier
gas. Any solute passes across the filament will not
cool it as much as helium does because helium has
the highest thermal conductivity. This results in an
increase in the temperature of the filament which is
related to concentration. The detector is simple,
nondestructive, and universal but is not very
sensitive and is flow rate sensitive.

32
Note that gases should
always be flowing
through the detector
including just before,
and few minutes after,
the operation of the
detector. Otherwise,
the filament will melt.
Also, keep away any
oxygen since oxygen
will oxidize the filament
and results in its
destruction.
Remember that TCD
characteristics
include:
1. Rugged
2. Wide dynamic
range (105
)
3. Nondestructive
4. Insensitive (10-8
g/s)
5. Flow rate sensitive

33
b. Flame Ionization Detector
(FID)
This is one of the most sensitive and reliable
destructive detectors. Separate two gas
cylinders, one for fuel and the other for O2 or
air are used in the ignition of the flame of the
FID. The fuel is usually hydrogen gas. The
flow rate of air and hydrogen should be
carefully adjusted in order to successfully
ignite the flame.

36
The FID detector is a mass sensitive
detector where solutes are ionized in
the flame and electrons emitted are
attracted by a positive electrode, where
a current is obtained.
The FID detector is not responsive to air,
water, carbon disulfide. This is an
extremely important advantage where
volatile solutes present in water matrix
can be easily analyzed without any
pretreatment.

37
Remember that FID characteristics include:
• Rugged
• Sensitive (10-13
g/s)
• Wide dynamic range (107
)
• Signal depends on number of carbon atoms
in organic analytes which is referred to as
mass sensitive rather than concentration
sensitive
• Weakly sensitive to carbonyl, amine, alcohol,
amine groups
• Not sensitive to non-combustibles – H2O, CO2,
SO2, NOx
• Destructive

38
Electron Capture Detector (ECD)
This detector exhibits high intensity for
halogen containing compounds and thus has
found wide applications in the detection of
pesticides and polychlorinated biphenyls.
The mechanism of sensing relies on the fact
that electronegative atoms, like halogens,
will capture electrons from a β emitter
(usually 63
Ni). In absence of halogenated
compounds, a high current signal will be
recorded due to high ionization of the carrier
gas, which is N2, while in presence of
halogenated compounds the signal will
decrease due to lower nitrogen ionization.

41
Remember the following facts about ECD:
1. Electrons from a β-source ionize the carrier
gas (nitrogen)
2. Organic molecules containing
electronegative atoms capture electrons and
decrease current
3. Simple and reliable
4. Sensitive (10-15
g/s) to electronegative groups
(halogens)
5. Largely non-destructive
6. Insensitive to amines, alcohols and
hydrocarbons
7. Limited dynamic range (102
)
8. Mass sensitive detector

42
Gas Chromatography
Lecture 38

43
Gas Chromatographic Columns
and Stationary Phases
Packed Columns
These columns are fabricated from glass,
stainless steel, copper, or other suitable
tubes. Stainless steel is the most common
tubing used with internal diameters from 1-4
mm. The column is packed with finely
divided particles (<100-300 µm diameter),
which is coated with stationary phase.
However, glass tubes are also used for large-
scale separations.

45
Several types of tubing were used ranging from
copper, stainless steel, aluminum and glass.
Stainless steel is the most widely used
because it is most inert and easy to work
with. The column diameters currently in use
are ordinarily 1/16" to 1/4" 0.D. Columns
exceeding 1/8" are usually used for
preparative work while the 1/8" or narrower
columns have excellent working properties
and yield excellent results in the analytical
range. These find excellent and wide use
because of easy packing and good routine
separation characteristics. Column length
can be from few feet for packed columns to
more than 100 ft for capillary columns.

47
Capillary/Open Tubular
Open tubular or capillary columns are finding broad
applications. These are mainly of two types:
• Wall-coated open tubular (WCOT) <1 µm thick liquid
coating on inside of silica tube
• Support-coated open tubular (SCOT) 30 µm thick
coating of liquid coated support on inside of silica
tube
These are used for fast and efficient separations but
are good only for small samples. The most
frequently used capillary column, nowadays, is the
fused silica open tubular column (FSOT), which is a
WCOT column.

48
The external surface of the fused silica
columns is coated with a polyimide film to
increase their strength. The most frequently
used internal diameters occur in the range
from 260-320 micrometer. However, other
larger diameters are known where a 530
micrometer fused silica open tubular column
was recently made and is called a megapore
column, to distinguish it from other capillary
columns. Megapore columns tolerate a larger
sample size.

54
It should be noted that since capillary
columns are not packed with any solid
support, but rather a very thin film of
stationary phase which adheres to the
internal surface of the tubing, the A
term in the van Deemter equation
which stands for multiple path effects
is zero and the equation for capillary
columns becomes
H = B/V + CV

55
Capillary columns advantages compared
to packed columns
1. higher resolution
2. shorter analysis times
3. greater sensitivity
Capillary columns disadvantage
compared to packed columns
1. smaller sample capacity
2. Need better experience

56
Solid Support Materials
The solid support should ideally have the
following properties:
1. Large surface area (at least 1 m2
/g)
2. Has a good mechanical stability
3. Thermally stable
4. Inert surface in order to simplify retention
behavior and prevent solute adsorption
5. Has a particle size in the range from 100-
400 µm

57
Selection of Stationary Phases
General properties of a good liquid stationary
phase are easy to guess where inertness
towards solutes is essential. Very low
volatility liquids that have good absolute and
differential solubilities for analytes are
required for successful separations. An
additional factor that influences the
performance of a stationary phase is its
thermal stability where a stationary phase
should be thermally stable in order to obtain
reproducible results. Nonvolatile liquids
assure minimum bleeding of the stationary
phase

58
Weight of liquid stationary phase * 100%
%Loading =
Increasing percent loading would allow
for increased sample capacity and
cover any active sites on the solid
support. These two advantages are
very important, however increasing the
thickness of stationary phase will affect
the C term in the van Deemter equation
by increasing HS, and therefore Ht.
Weight of stationary phase plus solid support

59
Generally, the film thickness primarily affects
the retention character and the sample
capacity of a column. Thick films are used
with highly volatile analytes, because such
films retain solutes for a longer time and
thus provide a greater time for separation to
take place. Thin films are useful for
separating species of low volatility in a
reasonable time. On the other hand, a thicker
film can tolerate a larger sample size. Film
thicknesses in the range from 0.1 – 5 µm are
common.

60
Liquid Stationary Phases
In general, the polarity of the stationary
phase should match that of the sample
constituents ("like" dissolves "like").
Most stationary phases are based on
polydimethylsiloxane or polyethylene
glycol (PEG) backbones:

62
The polarity of the
stationary phase can be
changed by
derivatization with
different functional
groups such as a
phenyl group. Bleeding
of the column is cured
by bonding the
stationary phase to the
column; or crosslinking
the stationary phase.
Liquid Stationary Phases
should have the
following
characteristics:
• Low volatility
• High decomposition
temperature (thermally
stable)
• Chemically inert
(reversible interactions
with solvent)
• Chemically attached to
support (to prevent
bleeding)
• Appropriate k' and a for
good resolution

63
Bonded and Crosslinked
Stationary Phases
The purpose of bonding and cross-linking is to
prevent bleeding and provide a stable
stationary phase. With use at high
temperatures, stationary phases that are not
chemically bonded or crosslinked slowly
lose their stationary phase due to bleeding in
which a small amount of the physically
immobilized liquid is carried out of the
column during the elution process.
Crosslinking is carried out in situ after a
column is coated with one of the polymers

65
In summary, stationary phases are usually
bonded and/or crosslinked and the following
remarks are usually helpful:
1. Bonding occurs through covalent linking of
stationary phase to support
2. Crosslinking occurs through polymerization
reactions to join individual stationary phase
molecules
3. Nonpolar stationary phases are best for
nonpolar analytes where nonpolar analytes
are retained preferentially
4. Polar stationary phases are best for polar
analytes where polar analytes are retained
preferentially

66
Gas Chromatography
Lecture 39

67
Gas-liquid chromatography
(GLC)
Packed columns are fabricated from glass,
metal, or Teflon with 1 to 3 m length and 2 to
4 mm in internal diameter. The column is
packed with a solid support (100-400 µm
particle diameter made from diatomaceous
earth) that has been coated with a thin layer
(0.1-5 µm) of the stationary liquid phase.
Efficiency increases with decreasing particle
size as predicted from van Deemter equation.
The retention is based on absorption of
analyte (partition into the liquid stationary
phase) where solutes must have differential
solubility in the stationary phase

68
Open tubular capillary columns, either WCOT,
SCOT are routinely used. In WCOT the
capillary is coated with a thin film (0.1-0.25
µm) of the liquid stationary phase while in
SCOT a thin film of solid support material is
first affixed to the inner surface of the
column then the support is coated with the
stationary phase. WCOT columns are most
widely used. Capillary columns are typically
made from fused silica (FSOT) and are 15 to
100 m long with 0.10 to 0.5 mm i.d.

69
The thickness of the stationary phase affects
the performance of the column as follows:
1. Increasing thickness of stationary phase
allows the separation of larger sample
sizes.
2. Increasing thickness of stationary phase
reduces efficiency since HS increases.
3. Increasing thickness of stationary phase is
better for separation of highly volatile
compounds due to increased retention.
•

70
Much more efficient separations can be
achieved with capillary columns, as
compared to packed columns, due to
the following reasons:
1. Very long capillary columns can be
used which increases efficiency
2. Thinner stationary phase films can be
used with capillary columns
3. No eddy diffusion term (multiple paths
effect) is observed in capillary
columns

72
Temperature Programming
Gas chromatographs are usually capable of
performing what is known as temperature
programming gas chromatography (TPGC).
The temperature of the column is changed
according to a preset temperature isotherm.
TPGC is a very important procedure, which is
used for the attainment of excellent looking
chromatograms in the least time possible.
For example, assume a chromatogram
obtained using isothermal GC at 80 oC, as
shown below:

73
Programmed 30 to 180°
Isothermal at 145°
Isothermal at 45°

77
The General Elution Problem
Look at the chromatogram below in which six
components are to be separated by an elution
process using isothermal conditions at for example
120 o
C:

78
It is clear from the figure that the separation is
optimized for the elution of the first two
components. However, the last two
components have very long retention and
appear as broad peaks. Using isothermal
conditions at high temperature (say for
example 200o
C) can optimize the elution of
the last two compounds but, unfortunately,
results in bad resolution of the earlier eluting
compounds as shown in the figure below
where the first two components are coeluted
while the resolution of the second two
components becomes too bad:

80
One can also optimize the separation of the
middle too components by adjusting the
isothermal conditions (for example at say 160
o
C). In this case, a chromatogram like the one
below can be obtained:

81
However, in chromatographic separations we
are interested in fully separating all
components in an acceptable resolution.
Therefore, it is not acceptable to optimize the
separation for a single component while
disregarding the others. The solution of this
problem can be achieved by consecutive
optimization of individual components as the
separation proceeds. In this case,
temperature should be changed during the
separation process. This is called
temperature programming gas
chromatography (TPGC)

82
First, a temperature suitable for the separation
of the first eluting component is selected,
and then the temperature is increased so that
the second component is separated and so
on. The change in temperature can be linear,
parabolic, step, or any other formula. The
chromatographic separation where the
temperature is changed during the elution
process is called TPGC. A separation like the
one below can be obtained:

84
Temperature Zones in GC
Three temperature zones should be adjusted
before a GC separation can be done. The
injector temperature should be such that fast
evaporation of all sample components is
achieved. The temperature of the injector is
always more than that of the column, which
depends on the operational mode of the
separation. The detector temperature should
be kept at some level so as to prevent any
solute condensation in the vicinity of the
detector body.

85
Gas-solid chromatography (GSC)
Gas-solid chromatography is based upon
adsorption of gaseous substances on solid
surfaces. Distribution coefficients are
generally much larger than those for gas-
liquid chromatography. Consequently, gas-
solid chromatography is useful for the
separation of species that are not retained
by gas-liquid columns, such as the
components of air, hydrogen sulfide, carbon
disulfide, nitrogen oxides, and rare gases.
Gas-solid chromatography is performed with
both packed and open tubular columns.

86
Molecular Sieves
Molecular sieves are metal aluminum silicate
ion exchangers, whose pore size depends
upon the kind of cation present, like sodium
in sodium aluminum silicate molecular
sieves. The sieves are classified according to
the maximum diameter of molecules that can
enter the pores. Commercial molecular
sieves come in pore sizes of 4, 5, 10, and 13
angstroms. Molecular sieves can be used to
separate small molecules from large ones.

87
Porous Polymers
Porous polymer beads of uniform size
are manufactured from styrene
crosslinked with divinylbenzene. The
pore size of these beads is uniform and
is controlled by the amount of
crosslinking. Porous polymers have
found considerable use in the
separation of gaseous species such as
hydrogen sulfide, oxides of nitrogen,
water, carbon dioxide, methanol, etc.

88
Quantitative Analysis
GC is an excellent quantitative technique
where peak height or area is proportional to
analyte concentration. Thus the GC can be
calibrated with several standards and a
calibration curve is obtained, then the
concentration of the unknown analyte can be
determined using the peak area or height.
The detector response factor for each analyte
should be considered for accurate
quantitative analysis.

89
Gas chromatographs are widely used as
criteria for establishing the purity of organic
compounds. Contaminants, if present, are
revealed by the appearance of additional
peaks. Qualitative Analysis is usually done
by comparison with retention times of
standards, which are very reproducible in
GC, provided good injection practices are
followed. Injection should be done with a
suitable Hamilton type syringe through the
heated septum injector till all needle
disappears, then the needle is drawn back as
steadily and fast as possible. This is
important for reproducible attainment of
retention times.

90
The Retention Index
The retention index, RI, was first proposed by
Kovats in 1958 as a parameter for identifying
solutes from chromatograms. The retention
index for any given solute can be derived
from a chromatogram of a mixture of that
solute with at least two normal alkanes
(chain length >four carbons) having retention
times that bracket that of the solute. That is,
normal alkanes are the standards upon
which the retention index scale is based.

91
By definition, the retention index for a normal
alkane is equal to 100 times the number of
carbons in the compound regardless of the
column packing, the temperature, or other
chromatographic conditions. The retention
index system has the advantage of being
based upon readily available reference
materials that cover a wide boiling range.
The retention index of a compound is
constant for a certain stationary phase but
can be totally different for other stationary
phases.

92
In finding the retention index, a plot of
the number of carbons of standard
alkanes against the logarithm of the
adjusted retention time is first
constructed. The value of the logarithm
of the adjusted retention time of the
unknown is then calculated and the
retention index is obtained from the
plot.
The adjusted retention time, tR’, is defined
as:
tR’ = tR - tM

94
Interfacing GC with other
Methods
As mentioned previously, chromatographic methods
(including GC) use retention times as markers for
qualitative analysis. However, this characteristic
does not absolutely confirm the existence of a
specific analyte as many analytes may have very
similar stationary phases. GC, as other
chromatographic techniques, can confirm the
absence of a solute rather than its existence. When
GC is coupled with structural detection methods, it
serves as a powerful tool for identifying the
components of complex mixtures. A popular
combination is GC/MS.

96
Mass Spectrometry
Analytical method to measure the
molecular or atomic weight of samples

97
Different elements can be uniquely identified by
their masses

98
MS Principles
Different compounds can be uniquely
identified by their masses
CH3CH2OH
N
OH
HO
-CH2-
-CH2CH-NH2
COOH
HO
HO
Butorphanol L-dopa Ethanol
MW = 327.1 MW = 197.2 MW = 46.1

99
Mass Spectrometry
• For small organic molecules the MW can be
determined to within 5 ppm or 0.0005% which is
sufficiently accurate to confirm the molecular formula
from mass alone
• For large biomolecules the MW can be determined
within 0.01% (i.e. within 5 Da for a 50 kD protein)
• Recall 1 dalton = 1 atomic mass unit (1 amu)

100
MS Principles
• Find a way to “charge” an atom or molecule
(ionization)
• Place charged atom or molecule in a magnetic
field or subject it to an electric field and
measure its speed or radius of curvature
relative to its mass-to-charge ratio (mass
analyzer)
• Detect ions using microchannel plate or
electron multiplier tube

101
Mass Spectrometer Schematic
Inlet
Ion
Source
Mass
Filter
Detector
Data
System
High Vacuum System
Rough pumps
Rotary pumps
Turbo pumps
Diffusion pumps
Vapor
HPLC
GC
Solids probe
MALDI
ESI
FAB
EI/CI
TOF
Quadrupole
Ion Trap
Mag. Sector
FTMS
Microch plate
Electron Mult.
PC’s
UNIX
Mac

102
Mass Spec Principles
Ionizer
Sample
+
_
Mass Analyzer Detector

103
Typical Mass Spectrum
• Characterized by sharp, narrow peaks
• X-axis position indicates the m/z ratio of a given
ion (for singly charged ions this corresponds to
the mass of the ion
• Height of peak indicates the relative abundance
of a given ion (not reliable for quantitation)
• Peak intensity indicates the ion’s ability to
desorb or “fly” (some fly better than others)

104
194
67 109
55
82
42
16513694
40 60 80 100 120 140 160 180 200
Abundance
Mass (amu)
Mass Spectrum
N
C
C
N
H
C
O
C
O
N
N
C H
C 3H
C3
H
Mass
Spectrometer
A Typical Mass Spectrum
Typical sample: isolated
compound (~1 nanogram)

107
+
_
+
_
e- e-
e-
+
+ ++
+
+
_
Electron Collector (Trap)
Repeller
Extraction
Plate
Filament
to
Analyzer
Inlet
Electrons
Neutral
Molecules
Positive
Ions
Electron Impact
Ionization Source

108
Mass
Filter
Inlet
Ion
Source
Detector
Data
System
High Vacuum System
Rough pumps
Rotary pumps
Turbo pumps
Diffusion pumps
Vapor
HPLC
GC
Solids probe
MALDI
ESI
FAB
EI/CI
TOF
Quadrupole
Ion Trap
Mag. Sector
FTMS
Microch plate
Electron Mult.
PC’s
UNIX
Mac

109
ion trajectory
not in register
(too heavy)
Ion
Source
Detector
ion trajectory
not in register
(too light)
ion trajectory
in register
S
N
Magnetic Sector Mass Analyzer
Electromagnet

110
Quadrupole Mass Analyzer
• A quadrupole mass filter consists of four parallel
metal rods with different charges
• The applied voltages affect the trajectory of ions
traveling down the flight path
• For given dc and ac voltages, only ions of a
certain mass-to-charge ratio pass through the
quadrupole filter and all other ions are thrown out
of their original path

111
Detector
Ion
Source
+
_
_
DC and AC
Voltages
Quadrupole Ion Filter
resonant ion
non-resonant ion
+

112
Mass
Filter
Inlet
Ion
Source
Detector
Data
System
High Vacuum System
Rough pumps
Rotary pumps
Turbo pumps
Diffusion pumps
Vapor
HPLC
GC
Solids probe
MALDI
ESI
FAB
EI/CI
TOF
Quadrupole
Ion Trap
Mag. Sector
FTMS
Microch plate
Electron Mult.
PC’s
UNIX
Mac

113
MS Detectors
• Early detectors used photographic film
• Today’s detectors (ion channel and electron
multipliers) produce electronic signals via 2ry
electronic emission when struck by an ion
• Timing mechanisms integrate these signals with
scanning voltages to allow the instrument to
report which m/z has struck the detector
• Need constant and regular calibration

114
Mass Detectors
Electron Multiplier

117
Club Drugs
Column: Heliflex®
AT™
-1ms
30m x 0.25mm x 0.25µm
(Part No. 15897)
Column Temp: 140°C (1min hold) to 300°C
(3min hold) at 10°C/min
Carrier Gas: Helium at 0.8mL/min (24cm/sec)
Detector: FID at 340 °C
1. Methamphetamine (0.18mg/mL)
2. 4-Methoxyamphetamine (0.18mg/mL)
3. 2,3-MDA (0.18mg/mL)
4. 3,4-MDA (0.18mg/mL)
5. 2,3-MDMA (0.18mg/mL)
6. 3,4-MDMA (0.18mg/mL)
7. 4-Bromo-2,5-dimethoxyphenethylamine (0.18mg/mL)
8. Ketamine (0.18mg/mL)
9. Phencyclidine (0.18mg/mL)
10. Cocaine (0.18mg/mL)
11. Flunitazepam (0.18mg/mL)

8 gas chromatography jntu pharmacy

Recommended

Recommended

More Related Content

What's hot

What's hot (20)

Viewers also liked

Viewers also liked (20)

Similar to 8 gas chromatography jntu pharmacy

Similar to 8 gas chromatography jntu pharmacy (20)

More from Dr. Suman Pattanayak

More from Dr. Suman Pattanayak (20)

Recently uploaded

Recently uploaded (20)

8 gas chromatography jntu pharmacy