Transcript Quantron Magellan QM3

OES Basics
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Elemental
Informations OES
 Basics of OES
 Instrumentation
 Calibration
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Elemental
Basics of OES
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Elemental
Historical Overview
 17th century (1666–1672):
Isaak Newton
Sunlight
1. Prism
Spectral colors
2. Prism
white light
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Elemental
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Elemental
Historical Overview
 Isaak Newton:
Light = Particle radiation
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Christiaan Huygens:
Light = Wave phenomenon
(like sonic waves)
Elemental
Historical Review
 1887:
Heinrich Hertz
Light = Small part of the electromagnetic spectrum
 1905:
Albert Einstein
Light = Particles (Photons)
The 1921 physics Nobel prize was awarded to Einstein in most
famous for his theory of relativity, but it is his discovery of photons
that is mentioned by the Swedish Academy.
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Elemental
Historical Review
 Both is true:
Light behaves somtimes like a Wave,
and sometimes as a Particle !
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Elemental
Historical Review
 1860: R. W. Bunsen and G. R. Kirchhoff
Existence of colors in flames =
Processes in the atoms
Different sort of atoms = Different colors in flames
Foundation Stone for the Spectral Chemical Analysis
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Elemental
Basics OES
 In the
Optical Emission Spectroscopy,
the atoms are exited by heat from an electrical discharge. The
arising light is being dispersed into spectral wavelengths and the
intensity of specific, atom related lines is measured.
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Elemental
Basics OES

Atomic structure
Niels Bohr theory
The atomic nucleus contains protons (+) and neutrons ().
In special orbits electrons (-) are moving around the
nucleus.
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Elemental
Basics OES
 If enough energy is transferred to the atom
an electron can be moved from one orbit (shell) to a higher on.
It is now in an “exited“ status
Energy transfer
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Elemental
Basics OES
 The electron´s position is not stable as long there is an unocupied
position in an lower orbit. It falls back in a lower orbit. It must
now get rid of the energy it got to move from a lower to a higher
orbit. This is done by emitting light (Photons).
Radiation
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Elemental
Basics OES
 Wavelenghts and -ranges
 Units
1 nm
1Å
=
=
10-9 m
10-10 m
 Ranges
Infrared range > 800 nm...
Visible range: 400-800 nm
UV-range: 200-400 nm
VUV-range < 200 nm...
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Elemental
Basics OES
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Gammarays
Xrays
UV
visible
Spectrum
0.01 nm
1 nm
100 nm
400-800 nm
Infrared
1 mm
Radio-
1m
1 km
Elemental
Basics OES
 Depending on the different possibilities of electron transfer between
shells there are several specific wavelenght for an atom.
 The OES uses the wavelength range
120 - 800 nm
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Elemental
Basics OES
Atomic lines and Ionic lines
 Atomic lines
• Exitation of electrons in neutral atoms
 Ionic lines
• Exitation of electrons in an ion (ionized Electron)
(atom which lost one or more electrons)
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Elemental
Instrumentation
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Elemental
Video Automatic system with grinding
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Elemental
Instrumentation I
Keyboard, Mouse, Printer
(PC not visible)
Start/Stop Button
Instrumentation
Sample Clamp
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Spark Stand
with sample
Elemental
Instrumentation II
Air Con
Power Supplies
Vacuum Pump
Integrator Boards
Vacuum Tank
Spark Stand
Read-out & Source
Controller
Source Box
Argon Block
Not visible:
Personal Computer
Keyboard, Mouse, Printer
Software Package
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Elemental
Instrumentation
 Main components are:
-
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Exitation system
Optical system
Readout system
Computer
Elemental
Instrumentation
 Components:
Exitation system
Optical system
Computer
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Readout
Printer
Elemental
Instrumentation
 Exitation system:
- Between electrode and sample surface an electrical discharge is
established
- Material is being evapourated, partly atomized or ionized.
- Atoms and ions are exited
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Elemental
Instrumentation
Exitation Source
 Digital generation of any current supply curves with max. 250 A peak
current
 Discharge 10 µs to 2 ms
 Max. 1000 Hz spark frequency
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Elemental
Instrumentation
 Optical System:
- The exited light from the exitation source is transfered into the
optical system
- It is dispersed into the wavelengths contained in the exited light
- The intensity of the atom dependend wavelenght is measured.
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Elemental
Instrumentation
sample
Entrance
Slit
Grating
Exit Slit
Electrode
CPM
detector
Exit Slit
Rowland
Circle
Exit Slit
CPM
detector
CPM
detectors
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Elemental
Instrumentation
OPTIC
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Elemental
Instrumentation
 Optical System:
Grating and slits are mounted on a circle (Rowland circle),
which diameter equals the concave radius of the grating.
The spectral lines are images of the entrace slit on the
position of a specific wavelength. They exist exactly on the
Rowland circle.
(Paschen Runge mounting)
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Elemental
Instrumentation
 Optical System:
- The entrance slit width is usually 10 µm, its hight up to 20 mm.
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Elemental
Instrumentation
 Optical System
 Grating:
As dispersive medium a concave grating between 1800 and 3600
groves/mm is used. The light is dispersed and reflected on the
surface of this grating.
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Elemental
Instrumentation
Exitslits and CPMs
Connection to
readout system
HV
Direct lightpath
Grating
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Entrance slit
Elemental
Instrumentation

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






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Channel - Photomultiplier (CPM)
Since 1995 on the market
Developed and produced in Germany
Compact
High sensitivity
High dynamic range
Extrem low dark current
High amplification
Wavelenght coverage: 110-850 nm
Elemental
Instrumentation
 Photomultiplier:
 CCD Detector (Charged Coupled Device)
Both detectors convert light into an electrical signal
(current).
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Elemental
CCD (Charged-Couple-Device)
 CCD detectors known from scanners and bar code readers
or Cameras
 Function based on semiconductor Technology
 Cheap detector
 Developed in early 1970‘s
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Elemental
CCD (Charged-Couple-Device)
CCD Basics
CCD imaging is performed in a three-step process:
1. Exposure, which converts light into an electronic charge at
discrete sites called pixels
2. Charge transfer, which moves the packets of charge within the
silicon substrate
3. Charge-to-voltage conversion and output amplification.
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Elemental
CPM (Channel-Photo-Mulitiplier)
© graphics by Olympus Microscope & Perkin Elmer optoelectronics
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Elemental
Instrumentation
CPM at Bruker Elemental OES
Wavelenght
1st order
Used
CPM
Used
Filter
800nm-580nm
963
GG475
580nm-540nm
934
GG475
540nm-317nm
Wavelenght
2nd Order
Used
CPM
Used
Filter
414nm-330nm
934
934
330nm-317nm
934
UG5
317nm-210nm
933
317nm-250nm
933
UG5
210nm-162nm
932
250nm-165nm
922
165nm-120nm
911
165nm-120nm
911
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Elemental
Instrumentation
Readout
 Developed by Bruker (Quantron) and Perkin Elmer
 Optimized on CPM detectors
 Frequency up to 250 kHz
 Single Spark Evaluation
(only with CPM)
 Time Resolved Spectroscopy with up to 4 windows in
any source parameter (only with CPM)
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Elemental
Instrumentation
 Readout system:
CPM/CCD
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Integrator
ADC
PC
Elemental
Instrumentation
 Instrument to measure intensities of light
- up to now the described instrument is able to measure
intensities of light emitted by the source system, dispersed by the
optical system and measured via the sensors by the readout
system.
- It is now an
“Instrument to measure intensities of light“
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Elemental
Calibration
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Elemental
Calibration
An “Instrument to measure intensities of light“ only by
calibration becomes an analytical instrument to analyze
concentrations of Elements in an sample.
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Elemental
Calibration
 The intensity of light related to an element is proportional to the
concentration of the element in the sample.
 The calibration is established by using calibration samples with known
concentration of elements inside.
 The analysis of unknown samples is related to the calibration with the
calibration samples. The method is a relative one.
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Elemental
Calibration
 Calibration samples
Calibration samples should have the following properties:
- The composition should be similar to the unknown sample(s)
- They should be homogeneous
- The concentration should be as “true“ as possible. This is the
case when using CRMs (certified reference material)
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Elemental
Calibration
CRM:
The composition is of such a sample is analyzed by 5 or more
independent laboratories
The manufacturer uses an international approved statistical
procedure to calculate the best average and the deviation
of this interlaboratory results. A certificate is part of the
sample which describes all procedures used and the results.
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Elemental
Calibration
 With CRMs and possibly customer samples (secondary standards or
RM) the instrument is calibrated.
 For different elements different wavelenght are selected.
 Rule:
- for low concentrations a sensitive line is selected
- for high concentrations a less sensitive line is used
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Elemental
Calibration
 Example of a calibration curve (Cu in steel)
% Concentration Cu
Intensity (x 1000)
X = Calibration
samples
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Elemental
Calibration
 From measuring intensities to display the concentrations in
%(weight) there are several steps of calculation.
This steps are explained next:
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Elemental
Calibration
 1. Intensity
 2. Intensity ratio
 3. IE (inter Element) Corrected intensity ratios
 4. IE (inter Element) Corrected standardized intensity ratios
 5. Concentration ratios
 6. Concentrations
 7. Typestandardized concentrations
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Elemental
Calibration
- Intensity ratio -
The intensity of a spectral line is divided by the intensity of the
„matrix element“. The matrix element is the element which is
50% or more in the sample. In steel its Fe. The intensity of the
matrix element is called reference intensity.
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Elemental
Calibration
- Intensity ratio -
 Why are ratios used?
The rationing compensates changings of the status of the instrument during
time. This changes are caused by:
- Changes of the excitation system (i.e. change in the sample composition)
- Pollution by condensate in spark stand
- Pollution of optical components (windows, lenses etc.)
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Elemental
Calibration
- Intensity ratio -
 Intensity changes are compensated by calculating the ratio:
Measurement now :
Measurement later :
Intensity Ni = 1000
----------------------------Intensity Fe = 10000
Intensity Ni = 900
--------------------------Intensity Fe = 9000
The ratio is in both cases 0.1
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Elemental
Calibration
- Intensity ratios -
 Intensity ratios :
- The intensity ratio is multiplied by a so called “typical
value“ to get numbers which are looking like intensities and
not like concentrations. It is just a “cosmetic“ procedure.
- The typical value is usually the intensity of the reference
element line running the “pure sample“, that means pure Fe
in steel matrix.
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Elemental
Calibration
- Intensity ratios  Example:
Int. element Cr
1000
-------------------------------- X typ. Int. Fe 10000 =
Int. Reference Fe 10000
1000
--------- · 10000 = 1000
10000
 Now the intensity has dropped 20 %
»
800
--------- · 10000 = 1000
8000
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Conclusion
Instrument is stabile!
Elemental
Calibration
 Corrected intensity ratio :
So called additive and multiplicative corrections are done to
the ratios:
- Additive interferences
caused by line interference
- Multiplicative interferences
caused by matrix effects
 WHATS THAT??
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Elemental
Calibration
 Additive interference:
The line of an other than the considert element is so close
that it adds a part of ist intensity to the intensity considert.
By carefull selection of the lines this can be reduced but
never eliminated.
 WHATS THAT?
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Elemental
Calibration
- Corrected intensity ratio Example of a line overlap (additive interference):
Mo
Mn
Exit slit
On the peak maximum of Mo there is a significant interference of Mn
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Elemental
Calibration
- Corrected intensity ratios -
X
X
X
X
X
X
The intensity caused by Mn must be subtracted (corrected)
from the intensity of Mo.
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Elemental
Calibration
- Corrected intensity ratio  Multiplicative interference:
Interference caused by physical and chemical properties of the
sample which influences the discharged plasma.
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Elemental
Calibration
 Corrected standardized intensity ratio:
During “standardisation“ the actual measured intensity ratios
(actual values) are transformed by mathematical calculations into
those measured during calibration (desired values).
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Elemental
Calibration
- Corrected standardized intensity ratios -
 Why standardizing?
Every spectrometer shows changing in the intensities with
the time. This changes have the same reason why ratioing is
neccessary:
- Changes of the exitation system
(i.e. change in the sample composition)
- Pollution by condensate in spark stand
- Pollution of optical components (windows, lenses etc.)
To be able to use the original calibration curves after those
changes standardizing is neccessary.
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Elemental
Calibration
- Corrected intensity ratio -
 For every calibration curve a sample with low concentration
(low sample) and one with high element concentration (high
sample) is selected.
 This samples are measured during the calibration and the
intensity ratios are stored as desired values.
 Performing a standardisation later, the measured intensity
ratios (actual values) are compared with the desired ones
and a transformation equation is calculated.
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Elemental
Calibration
- Corrected intensity ratio -
 Calculation:
Int. HSexpected - Int. LSexpected
Factor = -----------------------------------Int. HSactual - Int. LSactual
Int. HSactual * Int. LSexpected - Int. HS
expected
* Int. LSactual
Offset = ---------------------------------------------------------------Int. HSactual - Int. LSactual
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Elemental
Calibration
- Corrected intensity ratio  Factor and Offset are the coefficients for the transformation of actual
intensities into the intensities during calibration:
Standardized corrected intensity ratios =
corrected intensity ratios * Factor + Offest
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Elemental
Calibration

Concentration ratio:
- Since the calibration is done using concentration ratios
instead of concentrations the first result using the calibration
curve is concentration ratio.
- It is calculated:
% Element
---------------- · 100
% Matrix
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Elemental
Calibration
 Concentration ratio:
- The concentration of the matrix element is calculates as
100% - Sum(% elements)
- To calculate the matrix concentration it is neccessary that
almost all elements are analyzed by the instrument
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Elemental
Calibration
- Concentration  Concentration:
After calculating the matrix concentration the software calculates
each element concentration interactively for its concentration
ratio.
 Now the final CONCENTRATION is displayed
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Elemental
Example on instruments
Q2 ION
Q4 TASMAN
Q8 MAGELLAN
Q4 MOBILE
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Elemental
Automation, possible configurations.
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Elemental
Future?
Inclusion Analysis / Steel Cleanliness
Determination by Spark OES
Characterization of inclusions in steel by
OES Pulse Discrimination Analysis (OES-PDA)
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Elemental
Reference Method for Inclusion Analysis:
SEM/EDS with Bruker Quantax 400 EDS
Scanning electron microscope with
energy dispersive x-ray
spectroscopy
Universal method: differentiation of
carbides, oxides, nitrides, sulfides
Large observation area
Imaging method
Highest accuracy
Surface method, low penetration depth
(~1µm)
Costly, long measurement time (~310h)
Highly educated operating staff
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Elemental
Reference Method for Oxygen Analysis:
melt extraction with G8 GALILEO
Melt extraction with carrier gas
method for the determination of
oxygen
Accurate analysis of total oxygen
Fast measurement (~80s)
High analysed sample mass (~1000mg)
Demanding sample preparation
Limited to oxygen only
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Elemental
Rapid Method for Inclusions & Oxygen:
OES-PDA = MCI = Metal Cleanliness Inspection
Inclusion characterization & oxygen determination
by Optical Emission Spectrometry with Pulse
Discrimination Analysis
Complete elemental analysis
Determination of various oxide and sulfide inclusions
Calculation of total oxygen
Simple sample preparation (grinding w/ SiC paper or milling)
Fast measurement (~5s/burn, multiple burns recommended, e.g. 5x)
User-friendly software for „normal“ OES operator
Feasibility study advisable
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Elemental
Single Spark Evaluation
Identification of Coincidences
Example for single spark
signals with the Q8 Magellan
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Comparison of Methods
SEM/EDS
ON/(H)
OESMCI
Capital investment (approx. k€)
550
60
80
Operating costs
High
Medium
Low
Yes
Partly
No
1-3 µm
Complete
10 µm
200 mm²
Complete
7 mm² )*
10 h
80 s )*
5 s )*
Ease-of-use (instrument)
Complex
Medium
Easy
Sample preparation
Medium
Complex
Easy
High
Limited
Medium
Reference method / norm
compliance
Penetration depth (of sample),
approx.
Tested area (of sample), approx.
PDA/MCI-Measurement time,
approx.
Analytical performance / value
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Elemental
Thank you very much for your attention!
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Elemental
www.bruker-elemental.com
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Elemental