Introduction to mass spectrometry troublshooting operation and working

Mass Spectrometer-MS
(Ionization Techniques and Mass Analyzer)
Faisal Ghazanfar, PCSIR
Presented by
Faisal Ghazanfar
Senior Scientific officer,
APCIC, PCSIR Labs. Complex, Karachi

Chromatography-Technique

Agenda
 Mass Spectrometry
 Block diagram of MS
 Ionization Techniques for GC/MS
 Electron Ionization/Impact (EI)
 Chemical Ionization (CI)
 Ionization Techniques for LC/MS
 ESI Probe
 Working, Diagrams, operation
 APCIC Probe
 Working, Diagrams, operation
 Stack
 Summery

Conventional Definition
 Mass spectrometry (MS) is an analytical technique for
the determination of the elemental composition of a
sample or molecule. It is also used for elucidating the
chemical structures of molecules, such as peptides* and
other chemical compounds. ...
*polymer of Amino Acid

Another Definition
 An analytical technique that measures the mass /
charge ratio of the ions formed when a molecule or
atom is ionized, vaporized and introduced into a
vacuum. Mass spectrometry may also involve breaking
molecules into fragments - thus enabling its structure to
be determined
www.en.wikipedia.org/wiki/Mass_spectrometry

Why MS…
 It is used for determining masses of particles, for
determining the elemental composition of a sample or
molecule.
 Elucidating (clarification for explanation) the chemical
structures of molecules.

Simple Mass Spectrometer
All Instruments Have:
1. Sample Inlet
2. Ion source
3. Mass Analyzer
4. Detector
5. Data System
http://www.asms.org
LC/GC out

MS Block Diagram

LCMS/MS Detector (LCQ Advantage)
STACK
CONNECTION
WITH ESI
PROBE
LCMS

GC/GCMS
Ion source
Mass
Detector
Power supply
GC

MS-for GC

Faisal Ghazanfar, PCSIR 14
Sheath(nitrogen)
nebulized/spray
Auxilaryoutside ESI to
guide spray gas
Sweep gas prevent in
stack to enter other gas
Typical LCMS Detector (Black Diagram)

Main parts
 Ion input/production assemblies/Probes
COMMON IN GS AND LC
 Ions guided by ion optics
 Quadropole /Octopole separation
 Detector dynode

Mass Spectrometer Requirements
1- A stable Electric Power Source with 220 VAC
with 50 Hz and minimum current 20A.
2- Operating Temperature is 15 to 27 C deg.
3- Humidity range is 40% to 80%
4- Gases requirement
Helium Ultra high purity (99.999%) with less
than 1.0ppm Water, Oxygen and total
Hydrocarbons with (40+10) psi pressure.
Nitrogen High purity (99.%) with (100+20) psi
pressure. This is used as Sheath Gas, Auxiliary
Gas and Sweep Gas.

Ionization Techniques for
GC and MS
Gas-Phase Methods (common for GC/MS)
 Spray Methods (common for LC/MS)
 Electrospray (ESI)
 Atmospheric Pressure Chemical Ionization (APCI)

Electron Ionization
 Electrons are produced by heating a wire filament
that has electric current running through it.
 The electrons are accelerated to 70 eV in the region
between the filament and the entrance to the ion
source block.
 The accelerated electrons are then concentrated
into a beam by being attracted to the trap
electrode.
 Sample molecule is in perpendicular direction to the
electron beam.
 Ionized and pass to MS

Electron Impact
http://www.noble.org/PlantBio/MS/ion_tech_main.html

Electron Impact
Advantages
 Well-Established
 Fragmentation Libraries
 No Supression
 Insoluble Samples
 Interface to GC
 Non-Polar Samples
Disadvantages
 Parent Identification
 Need Volatile Sample
 Need Thermal Stability
 No Interface to LC
 Low Mass Compounds
(<1000 amu)
 Solids Probe Requires
Skilled Operator
(low picomole)

Chemical ionization
 Inside the ion source, the reagent gas is
present in large excess compared to the
Analyte.
 Electrons (produced by filament) entering
the source will ionize the reagent gas.
The resultant collisions with other
reagent gas molecules will create an
ionization.

Chemical Ionization

Chemical Ionization
Advantages
 Parent Ion
 Interface to GC
 Insoluble Samples
Disadvantages
 No Fragment Library
 Quantitation Difficult
 Low Mass Compounds
(<1000 amu)
 Solids Probe Requires
Skilled Operator

ESI Probe Assembly
This Electro Spray Ionization (ESI)
Probe Assembly accommodates
liquid flows of 1 ul/min to 1000
ul/min and produce very small
charged droplets that contain
sample ions.

HPLC to MS

ESI Probe Working Principle
1- Sample solution enters ESI needle, Where a high voltage
is applied.
2- ESI needle sprays the sample into mist of droplets that
are electrically charged at their surfaces.
3- The electrical charge density at the surface of the
droplets increases due to solvent evaporation from the
droplets
4- The electrical charge density at the surface of the
droplets increases to a critical point (Rayleigh Stability
Limit). At this critical point the droplets divide into
smaller droplets because the electrostatic repulsion is
grater than the surface station. This process is repeated
many times to form very small droplets.

ESI Probe Working Principle
5- From the very small high charged droplets, sample ions are ejected
into the gas phase by electrostatic repulsion
6- The sample ions pass through an ion transfer capillary, enter the MS
detector and are analyzed.
7- The rest of the material and liquid go out of the probe through the
waste out let.

ESI Process

ESI probe (Cross sectional view)

ESI probe

Rules for a good Electro Spray
 Keep the salts out of the solvent system
 Use the lowest possible HPLC flow rates
 Use organic/aqueous solvent system and volatile
acids and bases
 Optimize the pH value of the solvent system

Simple ESI

ESI Probe
stack

ESI
Advantages
 Parent Ion (direct
injection)
 High Mass Compounds
(>100,000 amu)
 Thermally Labile
Compounds (<0º C)
 Easy to Operate
 Interface to HPLC
Disadvantages
 No Fragmentation
 Need Polar Sample
 Sensitive to Salts
 Suppression
(low femtomole to zeptomole)

APCI Probe-Parts
1- APCI Sample Tube
2- APCI Nozzle
3- Sheath Gas Plumbing
4- Auxiliary Gas Plumbing
5- Vaporizer
6- Sample Inlet Fitting
7- Ceramic Heater Tube

APCI – Probe

APCI – Probe Exterior

APCI Probe-Features (A)
1-APCI is a gas phase (Soft) ionization
technique but not as soft as ESI.
2- It is use to analyze compounds of medium
polarity that have some volatility.
3- It is also use to analyze small molecules
with molecular weight up about 1500 u.
4- It is also very robust ionization
technique. That is way it is not effected
by minor charges in most variables, such
as charges in the buffers or buffer
strength.

APCI Probe-Features (B)
5- The gas phase Acidities and Basicities of
the analyte and the solvent vapor play an
important role in APCI process.
6- APCI process has two modes
- Positive Ion Polarity Mode
- Negative Ion Polarity Mode

APCI Probe Working Principle
1-The APCI nozzle sprays the sample solution into fine mist of droplets.
2- These droplets vaporized in a high temperature tube.
3- A high voltage is applied to a needle located near the exit end of the
tube.
4- This high voltage creates a corona discharge that forms reagent ions
through the series of chemical reactions with the solvent molecules and
the sheath gas (Nitrogen)

APCI Probe Working Principle
5- The reagent ions react with the sample
molecules to form sample ions.
6- The rest of the material, Solvent and
water molecules go out of the system
through waste out let.
7- The sample ions enter the mass
spectrometer and are analyzed.

Sample Ion Formation
Primary Ion Formation
e- + N2  N2
+ + 2e-
Secondary Ion Formation
N2
++ H2O  N2 + H2O+ H2O+ + H2O  H3O+ + HO
Proton Transfer
H3O+ + M  (M + H)+ + H2O
(Proton)

API–Source with APCI-
Probe and stack, capillary

Corona Discharge Needle

API-stack (Ion Source Housing)
1- Ion Source Housing seals the atmospheric
Pressure region of the API Source.
2- All probes (ESI and APCI ) are easily
interchangeable and mount to
the housing tool less mounts.

(Ion Source Housing) parts
1- Probes access door
2- Sheath Gas Inlet
3- Auxiliary Gas Inlet
4- Sweep Gas Inlet
5- Drain Port For Waste Liquid
6- High Voltage for Electro spray
needle (ESI), the Vaporizer and
corona
7- Safety Interlock Switch

Ion source housing

API – Stack (Parts)
1- Ion Sweep cone
2- Spray Cone
3- Drain Out let
4- Vent Prevent Ball
5- Heater and Heating Block
6- Ion Transfer Capillary
7- Extension Mount
8- Tube Lens
9- Skimmer
10- Tube lens and Skimmer Mounting

API - Stack

Simple APCI
http://www.rzuser.uni-heidelberg.de/~bl5/ency/ency.html

APCI
Advantages
 Parent Ion
 Insensitive to Salts
 Interface to HPLC
 Can use Normal Phase
Solvents
 Handles High Flow Rates
Disadvantages

Mass Analyzers
 Quadruple Mass Filter
 Quadruple Ion Trap

Quadruple Mass Filter and ion Trap
http://www.asms.org

Quadruple Mass Filter
Advantages
 Inexpensive
 Easily Interfaced to Many
Ionization Methods
Disadvantages
 Low Resolution (<4000)
 Low Accuracy (>100ppm)
 MS/MS requires multiple
analyzers
 Low Mass Range (<4000)
 Slow Scanning

Quadropole
Quadropole

Dynode
Dynode/Detector
Vacuum section-Inside view of MS

Electronics of MS

Ethene spectrum
(nis
tdemo) E
thene
10 12 14 16 18 20 22 24 26 28 30 32 34 36 38 40
0
50
100
14 24
25
26
27
28
29
H
H
H
H
Name: Ethene
Formula: C2
H
4
MW: 28
28 999 | 27 545 | 26 501 | 25 73 | 29 22 |
largest peaks:

Acetone
(nis
tdemo) Acetone
10 15 20 25 30 35 40 45 50 55 60 65 70
0
50
100
14
15
27
29 39
42
43
44
58
59
O
Formula: C3
H
6
O
MW: 58

Summery
 Ionization for GC/MS
 Ionization for LC/MS
 Electrospray (ESI)
 Atmospheric Pressure Chemical Ionization (APCI)
 MS
 Quadruple
 Dynode

Maintenance MS

Vacuum gas system

Rotary-pump
Main Parts
• Oil in-port
• Oil out-port
• Oil level eye/window
• Vacuum in and out
connections
• Additional oil

Turbomolecular pump
Max.
pressure

10-8 Pa
Cooling gas-
Argon
1300 mL/min
Speed
24600 rpm

Ion source cleaning
 uninstall ion sources such as EI,ESI prob/stack etc
 Remember connections, pipes, directions etc.
 Wear Gloves, mask, etc. to stop any contaminations
 Used HPLC grade methanol to clean
 Tissue, cotton bad etc. not used/ clean air/nitrogen et.
to dry parts
 Install ion assembly

 Change flamant
 Change magnetic
coils
 Cleaning ion path

High vs low vaccuum

Thank you
Q & A

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