Advanced Analytical Chemistry
Chapter 0: introduction
Chapter 1: X-rays
Chapter 2: Element Mass spectrometry
Chapter 3: Molecular Mass spectrometry
Chapter 4: Surfaces
Chapter 5: Radiochemistry
Chapter 6: Seminar I: X ray diffraction
Chapter 7: Particle Size Determination
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Chapter 0: Introduction
Course Content
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Lectures
◦ 1/10
◦ 15/10
◦ 29/10
◦ 12/11
◦ 26/11
◦ 10/12
◦ Slides: Toledo (Information in
English)
6 times 3 h, instead of 12 times 1.5h, English
Exam (70%)
Contact: Bram.Verbinnen@uantwerpen.be
Seminars (30%): 12h
◦ Exercises
◦ Guest lectures
◦ ….
◦  Dates: TBD, see schedule Toledo
Obligatory presence
Contact:
Antoinette Deschuytere
Part1: Spectrometry
 Atomic X-Ray Spectrometry (XRF)
 Molecular X-Ray Spectrometry (XRD)
 Atomic Mass Spectrometry (ICP-MS)
 Molecular Mass Spectrometry (…-MS)
 (Raman Spectrometry)
 (NMR-Spectrometry)
Spectrometry: you will always receive a spectrum. X axis will always be a spectrum.
Part 2: The study of Surfaces:
 Electron Spectroscopy (AES)
 Ion Spectroscopy (SIMS)
 Surface Photon Spectroscopy (SPS)
 Electron-stimulated micro-analysis methods (SEM/TEM)
 Scanning Probe Microscopy (STM/ATM)
Part 3:
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Particle Size Determination
Voltammetry
…
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OVERVIEW OF THE TECHNIQUES
Belangrijkste figuur van het vak! Classified according to the detection limit, resolution and the y-axis.
Detection limit: the lowest concentration that can be distinguished from the background.
Resolution: the smallest distance needed between two objects to see them apart from each other. If
you can distinguish them apart from each other: the resolution is lower than the distance between
the two objects.
Example: ICP-MS, if you want to measure As: 75 m/q, but there is also ArCl: 75 m/q. With a bad
detector (high resolution) we cannot see them apart, if we have a very low resolution (good) we can
see As: 74,9 and ArCl 75,4. has nothing to do with the detection limit because both signals can be far
above the detection limit.
For every technique that we are going to study: have an idea what the detection limit and spatial
resolution are, be able to compare two different techniques (relative, not absolute).
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Chapter 1: X-rays
 General:
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Measuring emission, absorption, scattering, fluorescence, diffraction of X-Rays
Determining elements: identification and quantification
Elements heavier than Na
X-rays: part of EM spectrum.
What can we do with x-rays? Different processes.
Fluorescence: incoming em wave, it is absorbed, secondary em wave emitted that has a lower energy
content than the incoming em wave, higher wavelength.
Scattering: verstrooiing, happens in all directions. All of these scattered waves can interfere with each
other, can show interference (constructive or destructive), most of them will destruct each other.
When you have constructive however, we call it diffraction, you can measure it in this case.
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X-Rays
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E = h*c/lambda
EM-rays between10-6 nm and 10 nm.
Used in spectrometry: from 10-2 nm to 2.5 nm
Use of continuous spectrum or line spectrum.
High energy = low wavelength. They all interact with matter on a different matter.
Gamma rays:
X rays: what can happen? You will expell an electron from an atom  ionization
UV-VIS: electron shift to higher orbital
IR: vibration
Micro: rotation
Radio: electron spin changes (not a lot of energy necessary)
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Producing X-Rays
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By impact of a beam of high energy electrons on a metal
By using primary X-rays to produce secondary X-rays by fluorescence
Radioactive sources
Sources of Synchrotron Rays
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Making X-Rays: The Continuous Spectrum
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Production of high energy electrons by heating a Cathode
Accelerating electrons towards a metal anode (target) using a high potential (e.g. 100
kV)
Electrons collide with the target and decelerate: transformation of kinetic energy in
radiation energy (photons)
Many collisions with different energy produce a continuous spectrum.
Is called “White radiation” or “Brehmsstralung”.
Cathode = negative. You produce high energy electrons with eg a sharp, needle like tip, by
applying an electric field between cathode and anode, you will accelerate the electrons
towards the positive anode, they collide with the target and they decelerate (lose
energy).
Incoming electrons will bend under the influence of the nucleus, the outgoing electron
will have a lower energy. The excess in energy is released under the form of X-rays while
bending around the nucleus.
There are several paths that the electrons can make, the different deflection angles
produce different X-ray frequencies.
If you have a lot of collisions, you get a continuous spectrum.
The atom from the nucleus around which the electron bends are specific X-ray source
metal atoms.
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Smallest wavelength (highest energy): l0
Complete transformation of electron kinetic energy in photon
Independent of target material, dependent on accelerating potential
Formula (Duane-Hunt): V. e = h. n0 = h.c/l0
Allows determination of h
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At zero intensity, you have lambda zero.
Higher energy of your outgoing x-rays the
more you go to the left, but intensity is zero.
All of you incoming energy is absorbed, you
had a collision with your nucleus and the
incoming electron has completely stopped.
Different acceleration potentials: difference
between energy before and after can have a
wider range. Intensiteit moet je zien als:
‘hoeveel electronen hebben x-rays uitgezonden
met die energie’. The difference is the
acceleration Potential.
50 kv acceleration potential has bigger curve.
Tongsten = wolfram
Lambda zero depends only on you acceleration
potential!!!
One of the ways in which you can determine
the planck constant.
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Making X-Rays: The Line Spectrum:
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Lines superimposed on continuous spectrum
Typical for elements with Z >23:
Very simple spectrum with 2 groups of lines: K and L
Remember: 1 A = 0,1 nm
Not only continuous spectrum, but also some lines superimposed on the spectrum.
These line spectra originate from the knocking out of an electron in the shell,
secondary electron is removed from is orbital. There is now a vacant place and can be
filled with an electron from a higher orbital, thus with higher energy. There is thus an
excess in energy, this is then expressed by releasing an x-ray. Difference between the
2 orbitals (vacant place vs where the replacement electron comes from) is always the
same, thus the line spectrum is always the same.
You give all the lines a name, and it depends from which orbital the electron is
knocked out (K-L-M orbitals). Alfa or beta refers to which electron has filled the gap
(one up is alfa, two up is beta).
Kalfa is lower in energy because it is placed at higher wavelengths. Not a statistical
distribution as a continuous spectrum.
The ability to see the line spectra is also dependent on you acceleration potential, if it
is very low you may not be able to (because lamda zero shifts to the right).
Atom number larger than 23, at least 11 electrons (at least 1 on the M orbital).
Only from atomic number 24 you have L
lines.
Elementen K en Na zijn interessant
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Lines disappear when accelerating potential (energy) too low.
Minimum required energy increases with atomic number (Z).
Comp. Molybdenum (from 20kV) and Tungsten (lines only starting from 70kV)
Energy required to see such lines increases with atomic number, influence of nucleus is
higher, you need more energy to expel an electron from its orbital.
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Lines are the result of electron jumps of inner electrons.
K series:
 Accelerated electrons collide with electrons from shell n = 1
 An electron is ejected forming an excited ion.
 Electrons from higher levels fall down and emit X-Rays.
You have a distribution on your energy levels, but it is much smaller than your
continuous spectrum, you still call it a line spectrum. There are different levels for
each orbital!!
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Increasing nuclear charge (Zeff) has an effect on energy needed to remove electrons
AND on difference between energy levels (shells).
Spectrum is INDEPENDENT of the physical or chemical state of atom (in compounds)
because it concerns only electrons not involved in chemical bonds.
You cannot distinguish with x-ray techniques in the chemical state of an atom with
this technique!! You will only expel electrons from the inner orbitals, they do not
define the chemical state, do not make bonds or ions. You will not touch the outer
electrons with this techniques.
Don’t touch outer orbitals, only inner orbitals, so you cannot distinguish between
chemical states
If the energy is high enough it can expell an electron!! To release a electron it has to
be exactly the right energy!
There will be a vacant place, an electron from a higher level will decent an there will
be secondary x-ray.
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Producing X-Rays
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By impact of a beam of high energy electrons on a metal,
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By using primary X-rays to produce seconday X-rays by fluorescence (see later),
 Primary x-rays can also expell electrons. You need a certain, well defined
amount of energy of the incoming beam to expel this electron. The incoming
x-ray beam has a very high energy, so not much expelling, but when it does,
there is a large excess of energy and that is all converted in kinetic energy of
the outgoing electron. Again a vacant place, replacement electron, emission
of a secondary x-ray.
Benefit over the first manner of making x-rays: you will not have a spectrum
of x-rays, you will only have a very narrow band of energies of your x-rays.
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Radioactive sources:
 Nuclear reactions produce excited nuclei.
 Relaxation of the nucleus produces gamma-rays.
 Nuclei can also capture electrons (from K-shell). Higher level electron fall
down to fill the space and produce X-Rays. Half-life of K-capture varies
from a few minutes to thousands of years.
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Sources of Synchrotron Rays:
 Electrons at high speed in magnetic field. The deccelaration (deviation) of
the electrons produces radiation (complete spectrum) of which X-rays.
 Link: http://www.esrf.eu/about/synchrotron-science/synchrotron-lightanimation
 Electrons emitted by an electron gun are first accelerated in a linear
accelerator (linac) and then transmitted to a circular accelerator
(booster synchrotron) where they are accelerated to reach an energy
level of 6 billion electron volts (6 GeV).
These high-energy electrons are then injected into a large storage
ring where they circulate in a vacuum environment, at a constant
energy, for many hours. Each time these electrons pass through an
undulator, a device consisting of series of alternating magnets, they
emit X-rays, which are directed along beamlines.
CERN: collider with principle of synchrotron
Synchrotron: you can also use it to produce x-rays
You accelerate electrons at high speed in EM field, you can slow them down
again and they produce x-rays.
Advantage of this method: you can control the magnetic field and the amount
of deceleration, you can determine the frequency of x-rays you obtain. You
can very good select one wavelength of x-rays.
Movie: electron will be accelerated, when it passes the beamline, some x-rays
will be emite. You can use those energy for experience, (expl. With x-situ you
can measure wich minerals there were. )
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X-rays and Matter
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Overzicht:
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Absorption
Fluorescence
Diffraction
Comparable with other optical methods
ABSORPTION:
 Techniques: Xanes, Exafs
X-rays that are entering an atom.
Certain amount of energy that is exactly high enough to expel an electron
from the orbital. Highest changes of absorption: exactly the right amount of
energy needed is given.
Even if the energy of the incoming x-rays increases, the changes that the x-ray
will be absorbed will be lower.
 Principle:
Transfer of energy from X-ray photon to electron.
Probability decreases with increasing energy.
Sharp change (K or L) corresponds to excitation of K (or L) electron to
the outside of the atom (without kinetic energy).
When energy is higher then the electron also acquires kinetic energy.
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 Mass Absorption Coefficient:
Law of Lambert-Beer:
 ln P0/P = µx with
 P0 en P: intensity incoming and transmitted radiation
 x : thickness
 µ : linear absorption coefficient : f(element, number of atoms)
Or also:
 ln P0/P = µMρx with
 ρ: density
 µM : mass absorption coefficient (cm2/g): only f(element)
 If several elements:
 mM = WAmA + WBmB + WCmC + …. (with W = %mass)
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Not on the exam, this technique is not further discussed.
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FLUORESCENCE:
 Principle:
Absorption of X-rays produces an excited ion
For instance with an empty K-shell
After a short time: relaxation to ground state by electron shifts.
This produces new x-rays. (fluorescence)
Wavelength is slightly greater (less energy):
 Incoming X-rays ionize atom completely
 Emission is only inside the atom.
Ex. Absorption of Ag happens at 0,485 A (K-edge) and emission results in
0,497 A and 0,559 A.
The wavelength of the emitted x-ray is slightly greater, you lose an amount of energy.
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DIFFRACTION:
 Principle:
X-rays (like other EM-radiation) interact with electrons of atoms resulting
in scattering.
In an ordered system (crystal) constructive and destructive interference
occurs (because distance between scattering centers = wavelength)
Result = Diffraction
In phase vs out of phase. Diffraction only happens when the scattered waves are
constructively interfered. If you have a crystal structure, you have multiple layers of
crystals, the distance between the crystal layers depends on the cyrstals.
When the difference between the path of the waves is a natural number of the
wavelength.
The extra pathlength that the wave has to travel has to be exactly a natural number
times the wavelength. Difference in pathlength depends on the distance between
crystal layers and the angle under which the incoming x-ray comes in.
 Bragg’s law:
If the difference in path length AP + PC = nl the waves are in phase along
line OCD (only reflection).
But AP = PC = d sin q
Therefore constructive interference if nl = 2 d sin q or
sin q = nl/2d
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Instruments
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Use of absorption, emission, fluorescence, diffraction
Comparable with other optical methods
Instruments contain same parts:
a) Source,
b) System for selecting a wavelength(range),
c) “Sample holder”
d) Radiation detector, transducer
e) Signal processor,
f) “Readout”.
a) Source for X-Rays:
 X-ray Tube:
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Target material:
 W, Cr, Cu, Mo, Rh, Sc Ag, Fe, Co,….
By heating the filament, you will release electrons, they will be accelerated, will be
forced from the negative anode to the positive anode. When they hit target material
 collision, deceleration for continuous spectrum.
You have to make sure that not too many of your x-rays are already absorbed 
beryllium window. Also nearly vacuum inside the tube.
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 Radioisotopes:
 Secondary fluorescence
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Selection of wavelength or spectrum:
 Filters
Filter: the Kbeta line will be completely absorbed by the filter. This is quite old and is not
used much today. You only need a very thin sheet of zirconium.
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 Monochromator
You can select the angle of the incoming x-rays to your crystals.
If you change the angle, you can select the wavelength of your x-rays that will be emitted to
your sample or transducer. Relationship sin(theta)= n*lambda/2d.
You need one device that rotates the crystal, and one that rotates the sample. Sample needs to
rotate with twice the speed. Important that you know it is 2teta
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Sample holder
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Measuring the radiation: Transducers
◦ Previously: Photographic detection
◦ Today: transformation of radiation (photons) in an electrical signal
“Photon counting”: transform a radiation quantum in a charge pulse that can be counted:
Overzicht:
Gas-Filled Detector
Scintillation Counters
Semiconductor Transducers
Gas-filled detector
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Gas: Ar, Xe, Kr
X-Ray: Ar  e- + cation
e- : ionizes several additional atoms
e- move to anode, cations (slower) to cathode
X ray enters gas filled chamber, when the x ray goes trough window, it hits the gas
and it will produce an electron and a cation and they are accelerated and will collide
with other gas atoms. They will ionize different additional atoms. Electrons will mote
to the anode. cations go the the cathode.
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3 types of gas-filled detectors:
 Ionization chambers
 Proportional counters
 Geiger tubes
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Number of electrons per photon depends
on the voltage applied. You have different
regions. For x rays we use the proportional
region, the amount of electrons that is
produced is proportional to the amount of
x rays coming in. Geiger counter cannot be
used, it’s just a plateau. Geiger counter 
checkt voor radioactieve stralen, das zo een
bakske da ze gebruiken! Let op 10 tot de
10de wow hoog getal, dus zelf kleine ray
wordt zelfs gemeten! Geiger region is a
plateau, geen verband helaas dus niet te
meten?
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V < V1: recombination
V1 < V < V2: Ionization: constant number of e-: not used for X-rays
V3 < V < V4: Proportional region: rapid increase of e- with voltage
V5 < V < V6: Geiger range: enormous amplification, but limited by ‘space charge’
counteracting the electric field, no distinction between type and energy of incoming
radiation
Proportional: number of electrons formed is directly related to the amount of x-rays
coming in.
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Dead time
◦ Result of positive space charge
◦ Charge needs to be dissipated before new pulse can be detected
◦ Typically
 50-200 µs for Geiger tubes: less used for X-rays
 1 µs for proportional counters: most frequently used
Dead time because there is such a magnification of your signal, is also present in
proportional region but much higher in Geiger region.
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Scintillation counters
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Scintillation = production of flash of light by passage of a particle (e.g. a photon)
Semiconductor Transducer
Important for detecting elements, not used for measuring molecules. Elemental
spectroscopy.
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Methods
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Fluorescence (XRF)
 Most used
 Because measuring emission is not practical (target must be in sample)
 Two types:
 WDXRF: Wavelength-dispersive XRF
 EDXRF:
Energy-dispersive XRF
 Advantages: fast, quantitative determination of elements (except very light
ones), non-destructive.
You should be able to compare XRF and ICPF!
 WDXRF: Wavelength-dispersive XRF
Wavelength Dispersive X-ray Fluorescence (WDXRF) is one of two general types of
X-ray Fluorescence instrumentation used for elemental analysis applications. In
WDXRF spectrometers, all of the elements in the sample are excited simultaneously.
The different energies of the characteristic radiation emitted from the sample are
diffracted into different directions by an analyzing crystal or monochrometer (similar
to the action of a prism dispersing different colors of visible light into different
directions). By placing the detector at a certain angle, the intensity of X-rays with a
certain wavelength can be measured. Sequential spectrometers use a moving
detector on a goniometer to move it through an angular range to measure the
intensities of many different wavelengths. Simultaneous spectrometers are equipped
with a set of fixed detection systems, where each system measures the radiation of a
specific element. The principle advantages of WDXRF systems are high resolution
(typically 5 – 20 eV) and minimal spectral overlaps.
For both: your sample is always bombarded with x-rays, all of the fluorated x-rays
come out of the sample at once. You have to distinguish between them, based on
wavelength or energy.
 EDXRF:
Energy-dispersive XRF
Energy Dispersive X-ray Fluorescence (EDXRF) is one of two general types of X-ray
Fluorescence techniques used for elemental analysis applications. In EDXRF
spectrometers, all of the elements in the sample are excited simultaneously, and an
energy dispersive detector in combination with a multi-channel analyzer is used to
simultaneously collect the fluorescence radiation emitted from the sample and then
separate the different energies of the characteristic radiation from each of the
different sample elements. Resolution of EDXRF systems is dependent upon the
detector, and typically ranges from 150 eV – 600 eV. The principal advantages of
EDXRF systems are their simplicity, fast operation, lack of moving parts, and high
source efficiency.
You select based on their energy content, eg bending in a magnetic field.
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Fluorescence (XRF)
 Most used
 Because measuring emission is not practical (target must be in sample)
 Two types:
 WDXRF: Wavelength-dispersive XRF
 EDXRF:
Energy-dispersive XRF
 Advantages: fast, quantitative determination of elements (except very light
ones), non-destructive.
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Absorption: not often used (mostly when heavy elements are present in a light
matrix) ex. Lead in Fuel
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Diffraction
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Oxygen calculated assuming all elements present as standard oxides:
Drawback: cannot measure very light elements, oxygen e.g. the oxygen that is
present in your samples will be measured as oxides. This is not always correct but it is
the standardized way of comparing them as their oxides.
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What Nasa does on mars:
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XRF matrix effects:
 Absorption of X-rays by the matrix
 Countered by:
 External and internal standard calibration
 Dilution of samples and standards
 e.g. fusion with a substance that absorbs X-rays only weakly
 Li-metaborate/tetraborate (9.75 g) for each 0.75g of sample
 Thin films
 Mathematical corrections
Matrix effects: matrix of the sample that you measure also absorbes x-rays. If you measure
gold, it will not always be on top of the surface, can also be slightly below the surface.
Secondary x-rays generated at the gold needs to penetrate the above layer, you will always
lose a part of the rays due to absorption.
You need to counter is, calibration, dilution.
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X-ray diffraction
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Mostly for crystalline structures,
Used for metals, polymers and other solids,
Also for organic molecules: vitamins, steroids, antibiotics, nucleic acids….
Also qualitative determination of compounds (>< elements)
X rays used in another way so you can extract different information from it.
ONLY ISO MOSTLY. Constructive interference can only happen in a crystalline structure!
Used a lot in geology, to determine cystal structures, XRD can be used for this. One of the
seminars will also focus on the XRD.
You can use it for quantitative and qualitative determination, how much is present and is it
present? This is used to measure compounds, not an elemental composition.
You hav an x ray source, focus on monochromator, then you are going shoot it at the crystal
that we are going to analyse. You are going to change the angle, and let it circle around the
crystal so that everytime one angle is selected. Then you will have constructive or destructive
interference, this depends on the type of crystal that is present in your sample.
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Different XRD peaks. First one SiO2, then quartz (also SiO2), cristobalite is also SiO2. you see that the
XRD patterns as a function of 2*theta, is different for the three different minerals, although they have
the same chemical formula. The distance between the crystal layers is different for the 3 SiO2’s, this
way you can distinguish. You have clear peaks for quartz and cristobalite. Glass however is not a clear
peak, glass is an amorphous material, reflected xrays will be scattered in all directions, no
interferences, all wil go to the detecter and you will get a very broad peak. For XRD you really need
crystalline materials.
Destructive interference next to the peaks, no signal.
Nieuwe powerpoint op Toledo met extra afbeelding voor die constructieve interferentie. It only
depends on your incoming angle combined with the distance between your crystal layers. Very
specific for one crystal structure.
Rechtsbeneden: x ray source, the xrays will go directly to your sample, you will rotate the device, you
select an angle and you detect which angle will give you constructive interference and you will get the
graphs.
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X RAY Diffraction Pattern
Diffraction pattern with indication of the minerals that contribute most to the most
important reflections. Zincite (‘Z’) was added as internal standard. The reflections of
anhydrite (‘An’), Halite (‘H) and Sylvite (‘S’) are also indicated.
You see a peak from zincite, that is used as an internal standard, to distinguish how much
amorphous material is present in the material that you want to measure. Zincite is 100%
crystalline, depending on the height of the signal that you get from the xrd, you can
distinguish how much of the sample is amorphous or cytsalline, you can also calculate back to
the whole sample.
You can quantify the concentration of the material in the crystalline material. Based on the
signal of the zincite, you can see here that almost 60% of you sample is amorphous.
The baseline is due to the amorphicity, it’s scattering in all directions, for every directions you
will have a baseline.
 Further refinement: Rietveld refinement
 Overlapping peaks
 Least-square approach
 Quantification possible
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Developed a method to quantify xrd analysis, they were able to determine how much of the
mineral was present. With xrays you can only measure the top layer, you have to make sure
that your sample is a very fine powder so that you have a homogeneous standard.
Limit of detection is not very high, if it is below 1%, you will not be able to detect it.
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In-Situ XRD
More applications: seminar (Gilles Mertens – Qmineral)
You can do in-situ measurements, scan along a certain 2theta, and you can see in real time
how a reaction proceeds. Makes use of the synchotron xrays, you need always a stable xray,
always at the same frequency with high energy. Used at cern in Geneva.
Zie filmpje
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EXAMPLE EXAM QUESTION !!
Some genius scientists from KU Leuven recently published an (equally genius) article; the two first
pages of this article are attached.
A)
In the boxed section ‘A’ in the ‘materials and methods’ section, the authors explain
the use of XRD for their experiments. Explain in detail the following principles, and
illustrate with a drawing (max 1 page for each principle):
 2Θ= 5° to 75°
 Monochromatic Cu Kα radiation
B)
The detector in this XRD instrument is a proportional counter. Explain the principle of
this detector, make use of a drawing. (max. 1 page)
C)
In the boxed section ‘B’, the authors describe that they measured the total amount
of Cr (at parts per billion level, with ICP-MS) and the amount of Cr(VI) (using a
colorometric method) by dissolving the samples in water and then performing the
analysis on the dissolved samples.
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Another scientist claims that they had better measured the total amount of
Cr in the solid material directly, by using XRF. Is this other scientist right?
Why (not)?
Which other technique could be used to measure Cr(VI) in the solid material
directly? What is the disadvantage of this technique?
Concerns the whole xray chapter. 2 pages of the article that he wrote.
1) Be able to tell what the 2theta means, with the goniometer etc
you use copper as a metal sheet, you use Kalfa and you select the wavelengths with monoch.
2) Proportional counter with drawing
3) Comparison between icp-ms and xrf. Ppb level!! It is not true, detection limit is only in the
0,1% with xrf and ppb is much lower. You need to refer to the first big drawing that relates
the different detection limits with the different techniques. Other surface techniques that are
used to distinguish the oxidation states? Last lessons.
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
2 years ago, exam question regarding this chapter
XRD
What does 2teta mean?
What does it mean; Monochromatic CU Kalfa?
Proportional counter?
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Chapter 2: Mass Spectrometry
Last year: GC-MS, LC-MS: Compound identification, you do not get elemental information.
Now we are going to study elemental MS, we should be able to compare this with xrf.
What do you need to perform MS? Spectrum as a function of mass/charge ratio, we need to bring our
elements in a charged state. The big difference between elemental and compound : we first need to
dissociate our compounds into elements, and then me need to ionize with ICP and then to the MS.
What is plasma? Gasious phases containing only ions, highly excited ions in a gaseous phase, they are
moving in an EM field, hence the inductively coupled plasma. Exctied ions can collide with the
incoming elements that you want to measure, then elements will be ionized. Plasma has high energy,
so its very easy to ionize. Other thechniques are not able to ionize so much of the elements.
Nu gaan we het gebruiken voor elemental onderzoek, vroeger geleerd als compound onderzoek.
Techiques already used: JCMS Liquid and glass chromatography. JCMS, LCMS…
Elemental or compounds ?
 COMPOUNTS, any organic compounds like methanol, ethanol…
This relates to the XRF bc this will give ELEMENTAL information.

General:
◦ Determination of elements: identification and quantification
◦ Advantages vs. optical methods:
• Much lower detection limits & BROAD linear detection range (see next slide)
• Simple and clear spectra
• Determination of isotope ratios
• Quick and multi-element
◦ Disadvantages:
• EXPENSIVE apparatus
• Instrument drift (up to 5 – 10% per hour)
• Interferences possible (see further)
What is inside and how much?
AAS: has a plateau that you will reach, the signal that you will reach is always the
same. Not true of Mass spectrometry, you have a linear line almost forever. Much
broader range in which you can measure. With optical techniques you have several
lines, much more difficult to distinguish the peaks that you want to measure. It’s
quick and multi-element. With aas using another lamp, new calibration liquid for
every new element. With ms you can do it all at once, you only need one calibration
solution.
Instrument drift: the signal that you are measuring will gradually decrease in time.
It’s completely normal that the signal decreases and that the concentration in
different measured solutions was the same. We will see also how this comes, you can
know how much the signal drift is and you can calculate back. It is quite significant.
28
The spectrum is always a function of mass to charge ratio. We will bring the element
that we want to measure in a CHARGED STATE.
Those elements we will ionize, we will use ICP, inductive coupled plasma.
What is plasma ? Gas phase with only ions… 4th phase.
This plasma is moving in a electro magnetic field. Those exited ions can collide with
the incoming elements. They will charge them, the elements you want to measure.
Used for: IDENTIFICATION and QUANTIFICATION. What is inside and how much.
After a time, you will get a plateau with ASS. With mass the line is lineair and the
range is way broader.
Instrument drift ?
The signal decreases after time. After one hour for example, the signal can be 10%
lower after ten hours. There are tricks to calculate that drift.

GENERAL PROCEDURE
◦
◦
◦
◦
Atomise
Conversion to ions (mostly +1)
Seperation based on m/z ratio
Counting the ions (plot relative intensity vs. m/z)
They should be charged +1 , when they are charged +2 there will be interference!!
Ions should be charged +1, then you can distinguish between the different isotopes.

ATOM MASS:
◦
◦
◦
◦
◦
Concept mass different from other methods because here we can distinguish different
isotopes
Mass expressed in amu (atomic mass unit) or Dalton (Da). 1 amu = 1/12 mass 12C-isotope
1 amu = 1,6605387 x 10-27 kg
Ar = relative atomic mass = how many times heavier than amu.
In atomic mass spectrometry: use of exact mass and not mean mass (based on isotope
composition).
29
For example:
12
C  6 protons and 6 neutrons, by definition this is 12 amu, ( atomic mass unit )
6
_________________________________________________________
13
C  6 protons and 7 neutrons, this is 13,0033 amu  But C12 has an
6
abundance of 98,9% and C13 is 1.1%. SO the average is 12.01 amu, as
seen in the PSE.
Isotopes differ in neutrons but they have an equal amount of protons.
12/6 C: 6 protons and 6 neutrons: 12 amu
13/6 C: 6protons and 7 neutrons. 13,003355 amu. By definition, this has a mass of 12
atomic mass units.
Based on the average composition: what is the amu of ‘C’? 12,01 amu because 98,9% C12
and 1,10% C13. It is based on the mass of the isotop itself.
We use a diffeerent concept about mass!
Isotope = dffer in neutrons but have an equal amount of protons

ATOMS: MASS AND CHARGE
◦
◦
◦
◦

Mass-charge ratio of an atomic (or molecular) ion
m/z = ratio between Ar (or Mr) and ion charge
Example:
m/z of 12C1H4+ = 16,0313/1 = 16,0313.
Usually charge is 1 and mass-charge ratio is just called “mass”
GENERAL PRINCIPLE
◦
◦
◦
◦
A mass spectrometer produces (starting from a sample) ions (usually with charge +1)
That will be separated based on the mass-charge ratio (or just mass)
The ions are produced by irradiation with electrons, photons, ions or molecules or even
by thermal or electrical energy
Negative ions can also be formed
Working in vacuum bc you don’t want your ions to interact with parts in the air.
That’s why there is a big vacuum pump.
Icp is very fit to produce ions with a charge of +1. if you charge all of you atoms
present in your sample, you need to separate them on their m/z ratio.
You will use allways a very high vacuum.
◦
◦
◦
Mass analyzer = separation of the ions = spectrum
Transducer = converting the ion beam in an electrical signal for treatment, storage
(memory) or display (screen)
Need for vacuum = no collisions
30

TYPES OF ATOMIC MASS SPECTROMETRY
◦
Quadrupole Mass Analyzers (most common type)
You have 4 rods, AC and DC that are imposed on these rods, by combination of those 2
you can select one m/z ratio that will pass trough the quadrupole and then go to the
transducer.
4 rods
AC and DC,
Split those 4 ods in 2 times 2 rods, the are place on a positive DC current
+
+
The light ones will pass in negative (low-pass)
Heavy ones will pass in positive region (high pass)
 combination fives a small window!!
negative and positive change together so ther ewill always be a small region!!
31
2 times 2 rods, 2 rods will always be placed on a positive direct current and the 2 horizontal
are negative. Positive are regarded as a high pass filter, the negative rods can be regarded as
a light pass filter, all the light elements will pass trough the negative rods. If you find the right
combination, you can select a very small window of masses that can pass trough all of the
rods.
You have a positive voltage: all the ions that are passing trough will always stay in the
middle, they will not tend to go towards the positive sides. There is always a AC
superimposed, the light elements are easily influenced by the AC because they have a small
momentum and they will hit the rods because the rods will sometimes attreact them and
sometimes not. Heavy elements will not be influenced because they have a very high
momentum, they will pass. Therefore, the positive rods are a filter for the heavy elements.
Otherwise for the negative rods, ions will be attracted towards the rods. AC will move away
the light elements from the rods, heavy elements will just collide with the negative rods, light
can pass so a low pass filter. If you combine those 2 you will always have a specific pass zone.
The AC and DC will always increase together. Based on the combination of the AC and DC, you
can select.
32
◦
Time-of-Flight Mass Analyzers
Shoot your ions trough a tube, if they all start together, they will spread out because of their
different mass. Not used a lot anymore.
◦
Double-Focusing Analyzers
Distinguish between different masses. First electrostatic analyser that will filter out
some masses, then magnetic analyser, very good filter, based on the curve in a
magnetic field you will select a mass/charge ratio.
33

DETECTION OF IONS = TRANSDUCER
◦
Overzicht methods:
 Electron multipliers
 Faraday cup
 Array transducers
◦
Electron multiplier:
All the dynodes are on different potentials, will release an elctron, is then accelerated
towards another dynode. The potential over the next one is higher than the previous
one. It gains more energy, every electron that will hit, 2 wil be knocked out. You get an
enormous amplification that you can then measure.
Disadvantage:
Signal decreases after some years.
◦
Faraday cup:
34
◦
Array Transducers:



Made up of large amount of transducers
Allows detection of several elements at the same time.
Microchannel Plates (voor EOID):
Shoots ions endlessly and it goes a lot faster than using one multiplier.
35
INDUCTIVELY COUPLED PLASMA MASS SPECRTROMETRY ( ICPMS )




Most used system since 1980.
Low detection limit, high selectivity, good precision and accuracy.
Simple spectra with isotopes of the elements.
Identification and quantification.
Carrier gas will be argon most of the times, will be used to make the plasma. You mix your
sample with carrier gas, then spray chamber. Torch is where the plasma is generated. All of
these is just under atmospheric pressure, you are working in vacuum. You need an interface
between the parts that are under atmospheric pressure and the parts that are under vacuum.
The interfaces are cones with very small openings.


Ionization: plasma
Plasma:
◦ 4th state of matter
◦ Ionized gas
◦ Particles react strongly
◦ Usually very hot
(6000 - 10000 K)
We use a very hot plasma.
All of the individual ions
have a high energy content,
will be used to ionise the
elements that you want to
determine. The gas that is
used most is argon. Plasma
will be made out of argon
positive and argon.
Plasma will be made out of
argon positive and argon ion
36

Plasma in ICP-MS
◦ Mostly Ar: Ar+ and e◦ In torch: concentric tubes
◦ Seed electrons by sparc
◦ e- move in electric field and collide with Ar
◦ Sample introduction; nebulizer
You have a second stream of plasma, you will also
have a third stream of plasma, you need also a
stream on the outer side to make sure that not everything gets heated.
Ions will be sent trough the interface and then onto the quadrupole and then to the
electron multiplier.
Electrons will be accelerated and will collide with the argon, will ionise the argon
atoms and will create the plasma. Stable plasma which you can send your analytes
trough. You need to heat it up 5mins to make the plasma stable.

Plasma ignition (video)
You need to heat it up 5mins to make the plasma stable.
(zie filmpje in slides!!)

Plasma ionization efficiency
For most elements It’s very easy to make 1+ ionic ions. For others: the ionization
efficiency is not high, you will not make a lot of positively charged ions, you cannot
measure a bunch of them. Argon very low ionization efficiency, still we use it for
making our plasma. It’s the most difficult to be ionized, needs a lot of temperature.
We need a very continuous stream of argon, no plasma without constant plasma.
Every element that passes trough the plasma will be certainly ionized (hier worden
dan de elementen in het draaggas argon bedoelt).
The big power of icp-ms is that we have a very good ionization.
37

Interface
◦ Between plasma and detector (vacuum)
◦ Sample and skimmer cone
◦ Signal drift! (due to salt build-up)
You always have 2 cones with a very small …
Not all of the ions will be transferred to your quadrupole. Only around 0,1% will
continue trough the cones.
◦
Signal drift due to salt build-up (signal suppression)
Salt build-up on the cones, openings become narrower and if 10% less ions
can pass, you signal will be 10% lower. You can correct for this, but why do
we have these high salt concentrations?
Acids that you use contain salts and they will all precipitate on the cones. You
can dilute your samples and then your average salt concentration is lower.
The picture is very extreme, if you want a better analysis with lesser drift,
diluting. But if you really want to measure low concentrations, you cannot
dilute and you just have to correct for the salt build up.
 Signal drift  correction with internal standard
 Typical internal standards: Be, Ga, In , Tl
 Not common in samples to be analyzed
 Whole range of PSE
We use an internal standard to correct for the signal drift.
The amount of signal decrease is not only related to the salt build up, you
should have internal standard that is always as close as possible to the
element that you want to measure.
Internal standard should not be present in the solution that you want to
measure. These 4 do not occur that often in a normal environment.
38

Introduction of sample and internal standard
Peristaltic pump, will be mixed and sent together to the plasma.
You already have a stream of argon, this makes that at the tip of your nebulizer, your
solution is nebulized, sprayed into torch with additional argon and also cooling argon.

Mass spectrometer
◦
Typically quadrupole followed by electron multiplier
39
You also have a peak of argon at 40. if you cannot measure 40 calcium because of the peak of 40
argon, you can measure another isotope, calcium will have an isotope at eg 41. there you will have
no interference, easier to distinguish, you can calculate back because you know the abundance.
You have double focusing, higher resolution that eg a quadrupole.
(zie filmpje in ICPMS in slides!)

MASS SPECTROSCOPY and INTERFERENCE
◦
Advantage of ICP-MS methods (vs. spectroscopy) is simplicity of spectrum: only a few lines
vs. several emission lines.
You see a lot of peaks, it is difficult to attribute which peak is from which compound.
Optical spectrum of a solution of
100 ppm Cerium
Mass spectrum of a solution
10 ppm Cerium
Sent trough an icp-ms, a lot clearer, but interferences are possible. Everything except
from the Ce+’s are interferences.
40
◦
BUT: there still are interferences in atomic MS:
 Non-spectroscopic matrix effects (drift due to salt build up)
 Spectroscopic effects due to the presence of ions with same mass (m/z) as
researched ion:
 Isobaric ions
 = isotopes with identical mass
 Examples:
113 +
In and 113Cd+
58 +
Ni and 58Fe+
 Solution :
Measure another isotope (e.g. 56Fe+) and from information
of relative composition calculate the interfering isotope. Can
often be done with software.
 40 argon and 40 calcium, isotopes with identical mass.

Polyatomic ions
 formation of polyatomic ions (such as 16O2+) with same mass as
researched ion.
 Examples:
14
N2+ and 28Si+, or 75As+ and 75ArCl+

Doubly charged ions
 Example:
138
Ba2+ and 69Ga+
 Measure another isotope

Oxide and hydroxide ions
 most important source of interferences.
 Formation of oxides and hydroxides of the researched ions and/or
the matrix.
There are still interferences. First of all: non spectroscopic matrix effects: because
of the present matrix in the sample, salt build up etc.
Spectroscopic effects: effects that you see when you look at your spectrum. 4
different types.
Ions that are made out of more than one atom. If you use HCl, Cl- will form ArCl+.
Double charged: if you have high barium contect in your sample, it’s a problem,
your signal will not always be the same due to the presence of barium or other
double charged ions.
41
◦
List of interferences:
Know the elements you want to detect. You see what types of interferences that can occur for
these elements .
◦
Dealing with polyatomic interferences:
 High resolution spectrometers
 Resolution (for mass spectrometers):
 R= m/m
 m en m+m= 2 particles with similar concentration that can just be
separated (10% valley-definition)
 C2H4+; CH2N+ (28,0187); N2+(28,0061); CO+; mass 28
 R= 28,0124/(28,0187 – 28,0061)~2200
The height of the valley between the two peaks can max be 10% of the total
height of the peak. Spatial resolution (not this), this is a resolution for MS:
average mass diviced by the distance (in mass) between the two peaks.
42
 Collision cell technology (CCT)
 Introduction of gases causes ion-molecule (reaction gas) collisions and
reactions
 Polyatomic ions or gas ions are broken up in parts or converted into atoms
that do not interfere, mainly by chemical reactions or charge transfer;
analyte ions pass almost unaffected
 NH3 can be used to eliminate many polyatomic interferences
 Ca: Ar+ + NH3= Ar + NH3+
Ca+: no reaction
+
+
 Fe: ArO + NH3 = Ar + O + NH3
Fe+: no reaction
+
+
 Cr: ArC + NH3= Ar + C + NH3
Cr+: no reaction
 Not ideal for all interferences, reactions with many analytes reduces
sensitivity; single gas does not give best performance
 H2 also often used
You build in an extra cell before you go to the quadrupole, there will be extra
collisions (gas with polyatomic interferences). In the collision cell arO eg will
collide with ammonia gas, you will have no more interference at m/z 56.
interfering elements: ArO will be splitted.
Gases can react with polyatoms or positively charged argon atoms, you split
the polyatoms into individual atoms, will not interfere anymore with the
elements that you want to measure.

Collision cell
 Mostly placed before the quadrupole
Physical chamber where your analytes are sent trough before entering
the quadrupole.
43
Interference of ClO on measurement of V and Cr
measured concentration (ppb)
◦
160
140
120
100
80
V51
use of CCT
(NH3/He = 6.1%)
60
Cr53
40
20
0
0
200
400
600
800
HCl in solution (ppm)
Interference of the polyatom ClO. Solution that only contains HCl, no V or Cr present.
It’s due to the polyatomic interferences ClO with m/z 51 and 53. there is only hcl in
your solution. With cct you can eliminate those signals, you will measure nothing
anymore.
What is the influence of using the CCT on the signal?
Interference of CaO on measurement of Fe
measured concentration (ppb)
◦
600.0
500.0
400.0
300.0
Fe56
use of CCT
(H2/He = 3.5%)
200.0
100.0
0.0
0
50
100
150
200
250
CaO in solution (ppm)
44
◦
Use:
 qualitive and semiquantitative applications
Semiquantitative is not correct, you can really use it for quantitative applications. You
need a calibration, for each element you have a different surface below the peak. It
does not mean that if you know the surface below a peak, that you know the
concentration, no, you need to calibrate. Each element has another ionization
efficiency, depends on that what the surface is below the peak. Also how well is the
mass analyser performing etc. You can use it for quantitative analysis. But you need a
calibration before this! It is important to calibrate it first and then you can calculate
the concentration that depends on the surface below the peak.
 Quantitative applications: concentration measurements using internal standards
and calibration curves.
Every element gives another count for 10 mg/ml e.g. you do not reach the plateau,
you always have a straight line, you can easily extrapolate to higher concentrations.
In AAS, you would say that you can only measure real concentrations that are within
this limit, for ICPMS you can safely assume that you can measure concentrations that
are a couple times higher than the highest measured concentration.
You use internal standards and a calibration curve. Typically you get an outcome like
on the right. Always 3 measurements, average, std, %std. beryllium and gallium are
used for correcting the drift signal. Std only 1 percent so that is quite good
45
 Measurements of isotope ratios.
 Used in carbon dating
 Applications:
 Archeology, geology (dating)
 Use of isotopes as tracers.
Isotope rations interesting for geology/archeology, you cannot measure carbon with
ICPMS, but you can use other elements to date some chemical materials. You can get
to know the age
Isotopes as tracers: important in radiochemistry, you can measure the activity with
ICPMS.
 Liquid samples:

Dilution with ultrapure water
 Conservation ( acidification )
 Solid Samples:
 Dissolution (digestion, acids) and dilution
 Laser ablation
99% of the times you use liquid samples. To conserve your samples you always use
acids (nitric acid). Hydrochlorid acid is not used due to the chlorine.
Solids: you first need to dissolve them, ‘digestion’, then you will dilute them. Dilution
step is important because if you use a lot of acids, there will be a lot of salts, and
those will deposit and cause interference when too little dilution is provided.
46
 Laser ablation (LA-ICP-MS)
Powerful laserbeam to physically sputter some matter, those are then sent towards
the plasma where they can be measured.
You always have a vision system, you can look at your sample. Laser source will
remove some of the solid material from your sample in very small particles, then send
in solid phase to your ICP, then sent to quadrupole and detector.

Laser Uv light (eg 213 nm )
Advantages:
+ Low detection limits
+ Small sample size ( less than 1 micro gram )
+ Small spot size
( 5 – 300 micro grams )
+ No sample preparation ( less matrix effects )
Laser uv light, you can do some spot analysis. If you do not know which one of
the 2 is coal or pyrite, you can use the spot analysis. Especially helpful with
precious compounds. You can direct your laser beam to one specific spot on
your material, different from dissolving because you do not know where the
material comes from with dissolving.
You can really scan a surface and measure on different spots the
concentration, you get a profile alongside you surface.
47
INTERMEZZO: ATOM EMISSION SPECTROMETRY

Excitation of atoms from ground state

Emission of light of specific wavelength

Measurement of emitted light

Excitation
◦
Flame (FAES)
◦
Plasma (ICP-AES)
Analyzing the emission of EM waves in a visible light range. You always excite your atoms
from the ground states, when they fall back they emit light of a specific wavelength, they
will measure this light.
Excitation with eg a flame, you do not need ionization. Flame or plasma can be used. In
this case the most powerful way to do this is by using a plasma at much higher
temperatures, you will be able to excite a lot more of those atoms.
Flame : detection limit will not be very low. If you use plasma, your detection limit will be
a lot lower.
You don’t need ionisation, only excite them!
That’s why we handle this chapter. Plasma is the best to excite them!! Plasma has much
higer temperatures.
48

Atom Absorption Spectrometry (AAS) vs. Atom Emission Spectrometry (AES)
Excite the calcium atom. AAS: you measure the amount of energy needed for the excitation of
the ca-atom. With AES: you measure the emitted light when the excited ca-atom falls back to
ground state. IMPORTANT TO REMEMBER!
◦
Flame-AES vs. ICP-AES:
AES is the abbreviation of 2 techniques. Augier electron spectroscopy is also possible.
If you work at the typical temps of flames, you won’t have a large excited fraction.
Big power of using the plasma. You can see at the table, ratio of excited atoms/
atoms in ground state!
You can see that when we work at a specific temperature from a flame the ratio isn’t
that high. But if you look at if when used a plasma the ratio is higher!!
49
◦
ICP-AES = ICP-OES
You use your plasma to bring your atoms into the ionized state. Detection system is
different, here you only need a system that can measure the emitted light. Nebulizer
with argon to cool. Almost same setup than ICPMS. You only need a system now that
can measure the light.
 ICP-AES
Advantages and disadvantages
 Detection limits between AAS and ICP-MS
 Broad linear range (105), better than AAS, equal to ICPMS
 Capable of measuring Cl, S, P (  ICP-MS)
 Multi-element analysis
 More spectral interferences than ICP-MS
 Less chemical (polyatomic) interferences
With ICP-MS, we could not measure Cl, S and P,
you needed to bring them to a +1 state, the
ionization efficiency is very low and thus difficult
to bring them for the +1 state. Here, you only need
to excite them, not +1 state. We can measure
different elements in one solution at the same
time. Much more difficult to interpret the different
lines, more difficult to find the elements you are
looking for. ICPMS: related to the ionisation! If
difficult  difficult to measure! For AES you only
have to excite them! Lines difficult to seperate!
50
CHAPTER 3: MOLECULAR MASS SPECTROMETRY
Already studied last year! Look at it again but we will look tot the different mechanics that can be
used to bring the elements into ionised state! Compare different techniques is very important!
We will not use a plasma because the temp is to high, you want information about the molecule!
Base peak = highest peak! You use it as arefference for the other ones so you set this peak to 100 en
set the other peaks into realtion.
“Describe the different techniques to bring a molecule to an inionized state. “
Plot with the mass to charge ratio. We will plot the intensity.
Only going to look at the different mechanisms that can be used to bring the elements into the
ionized state. Some of these techniques can be used to analyse surfaces. Important here to be able to
compare the different techniques to bring them into the ionized state. We will not use a plasma here,
temp is too high, not wanted that you have dissociation.
Plot the relative intensity to the m/z ratio. A lot of segmentation.

APPLICATIONS:
◦ Mass Spectrometry (in general) gives information on:
 Elementary composition,
 Structure of (in)organic, biological compounds,
 Composition of mixtures (qualitative and quantitative),
 Structure and composition of solid surfaces,
 Isotope ratios.

GENERAL PRINCIPLE:
◦ Example: ethylbenzene (C6H5CH2CH3)
◦ Compound (as vapour) is ionized using electron beam:
 C6H5CH2CH3 + e  C6H5CH2CH3.+ + 2e
◦ Formation of a molecular ion (radical) in excited state.
◦ Relaxation of this excited state leads to breaking of the molecule: fragmentation (ex.:
C6H5CH2+ by removal of CH3)
◦ Separation of ions based on m/z ratio.
Ionized because the release of an electron. The molecule needs to release some of it’s energy.
The large molecule will break up into several molecules. All of the fragments that remain will
be positively charged. The ones that will be positively charged can be identified in your mass
spectrum.
51

Mass Spectrum of ethylbenzene (normalized)
You can use several mass analyzers.
Base peak is used to compare. You set that one to 100. The other peaks will be
compared with that.
Just based on the removal of one electron from the compound, the original mass is
the same to that of the original molecule. Base peak is the highest peak, what do we
use it for? As a reference for the height of the other peaks, you set the abundance of
the base peak to 100.

Production of ions
Important overview:
◦
◦
◦
Gas phase: first evaporation, then ionization
Desorption: directly from solid or liquid phase.
Hard Sources or Soft Sources:
 Hard:
 High energy produces ions in high excited states: relaxation leads to many
fragments.
 Information about functional groups (structure).
52
 Soft:


Less fragmentation.
Information about molecular mass.
For hard ionization, you use agents that have a lot of energy, the ions that originate
from hard energy sources, also have high excited states. If you have a molecule in a
high excited state, the relaxation will lead to a lot of fragments, so a lot of peaks in
you spectrum. Highly energetic ion can break into many different parts. Useful
because some functional groups will always come from the parent ion, a lot of
information about functional groups.
Soft: less fragmentation, only splitting of one hydrogen atom e.g., this brings us
information about MM because the peaks will always be very close to the molecular
ion peak. Spectrum will not contain many peaks, concentrated around the molecular
ion peak. Know the difference! Hard: use agents that produce or have a lot of energy,
high excited states. Molecules highly excited states, the relaxation will release many
fragments . Spectrum will have a lot of peaks. many peaks with different…..
 information of functional groups
Soft: information of full molecule
◦
HARD vs SOFT IONIZATION
For the hard ionization, you do not see the MM peak anymore. You would never guess that
the molecule that you are analysing would be one-decanol. If you have a soft ionization
technique, a lot less peaks.
53
◦
Electron Impact Source
 Gas Phase Method: sample must be thermally stable and MM not too high: less than
1000 g / mol.
Gas phase method, simple to understand. The easiest way to make ions, important you
have to bring your analyte into the gas phase, they should be thermally stable. Your MM
can not be too high, it can require too much energy then.
You have you analyte on the left, then you have filament that is heated, then placing
them into an electric field. Electrons will be generated in the filaments and will be
accelerated towards the anode. You will have the cloud of analytes and the electrons will
collide with analytes and you get excited ions. Then towards mass analyser. This is a hard
ionization source. Afterwards the breaking happens before they go to the analyser. The
ionization will lead to one molecular ion that then will relax and split into a lot of different
smaller molecules. Easiest way to produce ions.
In gas phase (stable!), molecular mass should be below 1000g/mol.
Before they go to the mass analyser the excited ions falls back.
 Fragmentation is an advantage but sometimes the molecular peak disappears
completely
Learns you a lot about the different functional groups, molecular peak disappears
sometimes. 2nd graph: molecular ion peaks are gone.
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◦
Other method: Chemical Ionization
 Gaseous molecules are ionized using ions (formed out of a gas using electrons) ex.:
methane.
 Advantage: soft method.
 Ionization of reagent gas
 CH4 + e- → CH4+ + 2 e
CH4+ + CH4 → CH5+ + CH3

CH3 + CH4+ → CH3+ + CH4
 CH3+ + CH4 → C2H5+ + H2
 Reaction with analyte
 CH5+ + MH → MH2+ + CH4

C2H5+ + MH → M+ + C2H6
You use a gaseous molecule that is first ionized. First ionise your methane, then this methane
will ionize your sample. All kinds of different types of ionized methane molecules. This step
with methane is necessary because if you directly use electrons, you are in the electron
impact mode. Here you are going to capture first a part of the energy, the ionized methane
molecules have a lot lower energy content, this is thus a soft ionization method. If you want
information about MM, you will use a method like this.
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◦
Other methods: Field Ionisation
 Field Ionization = formation of ions in a strong electrical field
around a “Carbon Microneedle Emitter”
 When EI can’t be used
 Soft ionization
Why that shape ? More surface. No direct contact between ions and needles.
Important is that the reaction occur at the tip. You need a very fine tip. Why is that ?
Specific surface is large.
Electrical field: voltage applied over a surface. You will have a very high Ef at the tip.
Positive charge at the tip of those needles. It will extract one electron from the
analyte molecule.
Field ionization, use a strong electric field around a carbon microneedle emitter. The
needle is formed like that to have more surface, the interactions occur at the very tips
of the needle. Specific surface there is very large, the definition of an electrical field is
the voltage applied over a specific surface, there is a large electrical field there.
We will bring the molecules in the neighbourhood of those tips, the positive tips will
extract one negatively charged electron from the orbital of the atom. The atom
becomes positively charged.
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◦
Desorption methods
 For materials that don’t evaporate or thermally
unstable.
 Apply energy in solid or liquid and remove ions
directly
 Results in simple spectra
 Example: MALDI
 Matrix-Assisted Laser Desorption
Ionization
New technique for solids and liquids.
We apply energy directly to the solid or liquid. The
power of the laser is too strong to send it directly
to the compounds, we have to make sure that we
keep the integrity of the molecules and do not split
them into atoms. Therefore we use a matrix, to
absorb a part of the laser energy to make sure that the molecules are still molecules
after they are hit. They also prevent that your analytes agglomerate and they protect
the destruction of your analytes.
 MALDI
 Matrix used to
 Absorb laser energy
 Prevent analyte agglomeration
 Protect analyte destruction by laser beam
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 Electrospray ionization: LC-MS
Electrospray, mostly used in LC. You have a voltage over the solution where your
analytes are dissolved in, also a counterelectrode.
The needletip will spray the solution with your analytes into a vacuum zone, they will
form very large droplets, many analytes will be dissolved into a matrix. On the outside
there will be the positive charge, the solvent that you use will start to evaporate due
to the heat. The surface charge will become higher and higher and at a given time,
the surface charge will become too high. The droplet will break into several smaller
droplets. Until you only have your analyte left which is now an ion.
 Field desorption
 Comparable to field ionization
 Secondary-ion Mass Spectrometry (SIMS)
 See later (measurement of surfaces)
 Plasma desorption
 Fast atom bombardment
 Thermospray ionization
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
Applications of Mass Spectrometry
Mostly organic molecules, not so important.
◦
◦
◦
Identification of pure compounds
 Determination of MM,
 Determination of Molecular formulas from mass determination,
 Determination of Molecular formulas from isotope ratios,
 Identification using comparison spectra (database),
Analysis of mixtures
 Coupled to gas chromatography
 Coupled to capilary elektrophoresis
 Tandem mass spectrometry
Quantitative determination in complex mixtures
 Organic (petroleum, pharma, bio…)
 Polymers,
PMMA
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CHAPTER 4 : STUDY OF SURFACES
 3D-pictures
Overview

Part1: Spectrometry
◦ Atomic X-Ray Spectrometry (XRF)
◦ Molecular X-Ray Spectrometry (XRD)
◦ Atomic Mass Spectrometry (ICP-MS)
◦ Molecular Mass Spectrometry (…-MS)
◦ (Raman Spectrometry)
◦ (NMR-Spectrometry)

Part 2: The study of Surfaces
◦ Electron Spectroscopy (AES, XPS)
◦ Ion Spectroscopy (SIMS)
◦ Surface Photon Spectroscopy
◦ Electron-stimulated micro-analysis methods (SEM/TEM)
◦ Scanning Probe Microscopy (STM/AFM)
◦ Surface area analysis

Part 3
◦
◦
◦
◦
Particle Size Determination
Voltammetry
Radiochemistry
…
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
Part 2: Study of surfaces:
Classification of surface analysis techniques
◦ Spectroscopic: detected (secondary) beam:
 Electron (AES, XPS, EELS)
 Ion (SIMS, RBS)
 Photon (ellipsometry, SPR)
◦ Microscopy: primary beam
 Electron-stimulated methods (SEM, TEM)
◦ 3D techniques
 Scanning Probe Microscopy (STM, AFM)
◦ Other
 Surface area analysis (BET)

DEFENITION OF SURFACE
◦ Boundary between solid and
 Vacuum,
 Gas
 Liquid
◦ That part of a solid that has a different composition than the average bulk.
◦ Not only the top layer but also underlying transition layers with gradually changing
composition.
◦ That part that is observed using a particular technique.
Examples: oxidation layer, fouling catalyst:
◦
◦

Before 1950
 Methods to determine the physical properties of a surface:
 Images,
 Adsorption isotherms,
 Roughness
 Reflectivity
 …
After 1950
 Also measurements of chemical compostion using spectroscopic method.
METHODS FOR SURFACE MEASUREMENTS
◦
◦
Qualitative and quantitative CHEMICAL determinations of surface
Dimensions: from a few tenths of nanometers to several nanometers
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