CIC Photonics
IRGAS Training
Schedule - Day 1
FTIR analysis
–
–
–
–
IR spectrum
Michelson interferometer
Fast Fourier transform and corrections
Interferogram, single beam spectrum, absorption spectrum and
transmission spectrum
– Beer’s law
– Instrument resolution
– Quantification analysis-Classical Least Squares introduction
Hardware description
– Bomem WorkIR
– Instrument purge
– Manual manifold
SPGAS software
– IRGAS 100
– IRGAS configuration manager
– Data retrieval
Schedule - Day 2
SPGAS software cont.
– Qmax – quantification manager
– IRGAS spectra reprocessing software
Hardware installation
– System power
– Pipe installation
– Instrument purge
Software installation
– IRGAS software
– Bomem Ethernet drivers
– System verification
System maintenance
FTIR Analysis
Tab 1
Light Spectrum
Infrared is invisible light ranging from 1mm to 750nm in wavelength
Infrared light can be divided into three parts:
– Far infrared -1mm to 10µm
– Mid infrared - 10µm to 2.5µm
– Near infrared - 2.5µm to 750 nm
Infrared (IR) Spectrum
IRGAS System mid infrared range
– 2.5µm – 25µm in wavelength
– 4000 cm-1 – 400 cm-1 in wavenumbers
Wavelength (λ)
– Wavelength = (1/wavenumber)*10,000
Wavenumber (cm-1)
– Wavenumber = (1/λ)*10,000
IR Molecules
Not every molecule absorbs infrared light
– Monoatomic
He, Ar, Ne, etc…
– Homoatomic diatomic
N2, O2, H2, etc…
– N
N
Molecules that do absorb infrared light
– Water is a good example
O
H
H
Michelson Interferometer
2
1
3
4
Step 1: Beam leaves IR source and hits beamsplitter where it is sent
straight through and at a 90° angle
Step 2: The 90° angle beam hits a fixed mirror and is sent back to the
beamsplitter
Step 3: The beam that went straight through hits a movable mirror and is
sent back to beamsplitter
Step 4: The two beams recombine, go through the gas cell and travel to the
detector
Michelson Interferometer
When AB=AC the phase of the frequencies look the same
When AB=AC+1/4λ, then the phase of the frequencies are opposite
in regards to maximums and minimums
AB
AC
Michelson Interferometer
When AB=AC and the two recombine you
get stronger maximums and minimums
When AB=AC+1/4λ and the two
recombine they cancel one another out
and result in a flat line
ABB Bomem Michelson
Interferometer
It has two sets of mirrors that move by a
pivoting motion
This design is called a wishbone
configuration
– This configuration is more robust
It can be placed in any orientation
This configuration only has to be smooth at one
point vs. the traditional interferogram that has to be
smooth along a rail
ABB Bomem Michelson Interferometer
ABB Bomem Michelson Interferometer
IR
Source
Laser
Fast Fourier Transform
The highest peak intensity is attained when AB=AC
The maximum of the highest intensity peak is called the zero path
difference (ZPD) point
After the interferogram has been created by the instrument, the Fourier
transform is applied to it, which then results in a single beam spectrum
Inte r fer ogr a m
ZPD
1
0
V
o
l
t
s
-1
-2
-3
3 20 0
3 00 0
2 80 0
2 60 0
2 40 0
Data Points
2 20 0
2 00 0
1 80 0
Single Beam Spectrum
28
26
24
22
Arbitrary units
20
18
16
14
12
10
8
6
4
4 000
3 000
2 000
W ave num bers (c m-1 )
1 000
Single Beam Spectrum
28
26
24
22
20
%T
18
16
14
12
10
8
6
4
4 000
3 000
2 000
W ave num bers (c m-1 )
1 000
Single Beam Spectrum
28
26
24
22
20
%T
18
16
14
12
10
8
6
4
4 000
3 000
2 000
W ave num bers (c m-1 )
1 000
Single Beam Spectrum
28
27
26
25
24
23
22
21
%T
20
19
18
17
16
15
14
13
12
11
10
9
2 000
1 500
W ave num bers (c m-1 )
Transmission
The ratio between the sample and the background
spectrum
S
Transmissi on    *100
 B
Transmittance Spectrum
1 10
1 00
90
80
Absorbance
70
60
50
40
30
20
10
0
4 000
3 000
2 000
W ave num bers (c m-1 )
1 000
Chemometrics
Based on the transmission spectrum
chemometrics can be applied
– Chemometrics: The application of statistical
and mathematical methods for the design or
optimization of chemical experiments and for
the efficient extraction of information from
chemical data
Two types of chemometrics:
– Qualitative (identification)
– Quantitative (quantity)
Absorbance
0 .50
0 .45
0 .40
Absorbance
0 .35
0 .30
0 .25
0 .20
0 .15
0 .10
0 .05
4 000
3 000
2 000
W ave num bers (c m -1 )
100


Absorbance  log 

 transmissi on 
1 000
Beer’s Law
Says that concentration is directly
proportional to absorbance (linearity)
Beer’s law equation is A= abC
– Where A = absorbance
a = absorptivity of the molecule
b = pathlength that the light travels
C = concentration
Instrument Resolution
The more points per peak the higher the
resolution
The higher the resolution the more noise,
but the better peak separation
Common resolution used for an ABB
Bomem instrument is 2 cm-1
Ranges between 1 cm-1 to 128 cm-1
Why Do We Need a Gas Cell
Intensity of a peak is directly related to the
# of moles in a sample
In the same area:
– Solid will be very packed
– Liquid will be less packed
– Gas will be even less packed
Long Path Gas Cell
Objective mirrors
¼” VCR fittings
Field mirror
Window retainers
4Runner 6 Meter Gas Cell
Gas Cell Mirrors
Objective
Mirrors
Field Mirror
Transfer
Mirrors
Source
Top view of field mirror
IR Beam Path
Classical Least Squares (CLS)
The base equation is As = Ac*K + e
– Where As = sample absorption
Ac = calibrated absorption
K = concentration
e = noise
Using the above equation find K that
minimizes e
To minimize e we use the CLS method
In this situation there are more equations
then variables
Classical Least Squares (CLS)
To simplify matters we assume that e = 0
– The equation then becomes: As = Ac*K
Matrix form:
As  Ac * K
 As1   Ac1 
 As   Ac 
 2  2
 .   . 


*K
 .   . 
 .   . 

 

 Asn   Acn 
Classical Least Squares (CLS)
In order to solve for K (Ac-1*As = K), Ac
needs to be an inverse matrix
– Therefore: AcT*As = (AcTAc)*K
(1x1) = (1x1)*K
Problems with Initial CLS Approach
Baseline becomes unstable throughout the
day
– It can shift, slope, or curve
These changes can be compensated for in
the calibrated absorption matrix
Classical Least Squares (CLS)
Accounting for these baselines changes the
equation
– The eqn. becomes: As = AcK1+
 As1 
 Ac1
 As 
 Ac
2
2



 . 
 .




.


 .
 . 
 .



As



n

 Acn
1
1
1
.
.
.
.
0
.
.
1
1
1
.

.
 * K1
0
.

1

K2+
K2
K3
K3+
K4
K4 
The calibrated absorption matrix can be increased
to accommodate the number of species being
tested
Weighted Multi-band CLS
A more complex version
of the standard CLS
The spectrum is
separated into bands
– Each band is then
calculated
After all the bands are
calculated they are added
in a weighted averaged
fashion
– The ones with the highest
error and lowest signal are
counted for less then the
ones with the lowest error
and highest signal
Hardware Description
Tab 2, 3, & 4
ABB Bomem WorkIR
Manual Manifold
Purge Gas In
Process Gas In
Check Valve
Maintenance Valve
Process Gas Out
Permeation Box
Purifier
Gas Cell
Nitrogen Outflow
Check Valve
Pressure/Flow
Transfer Optics
Gas Flow
Optical Path
Pressure/Flow
Spectrometer
Nitrogen Outflow
Manifold Parameters
Flow Restrictor
– A flow of 30 psi in will give a flow of 5 slpm to
the instrument
Purifier
– Gives dry N2 to below 2 ppb
– Has a lifetime of more than a year if it is used
24/7
Vibrations
There are a number of designs of
suspension systems to counteract
vibrations
These designs help to keep the data from
being affected by a simple bump of the
instrument bench
Typical Gas Cells
Have a flow similar to turbulent flow and have a
longer residence time
Gas in
Exhaust
Laminar Flow Gas Cells
The flow is like a waterfall
– Therefore there will be less turbulence
Heated laminar flow gas cells
– The gas is in contact with the walls letting it reach a
temperature similar to the gas cell prior to entering the
cell
Gas in
Gas Cell Flow Diagrams
f/5 Beam Geometry
d
Focus
ed IR
Beam
f.l.
f / # = f.l.
d
f.l. = focal length
d = beam diameter
The higher the f / #, the smaller the objective
mirrors, the more light that is lost, the smaller the
throughput
SPGAS Software
Tab 6, 7, 8, 9, & 10
Specialty Gas Analysis Software
(SPGAS)
IRGAS 100 system
– Collection & quantification
Qmax
– Quantification manager
IRGAS Configuration Manager
– Configures parameters
Quantification Reprocessing Tool
– Recalculating spectra
IRGAS 100 System
After opening the software the first window
is the monitor screen
– On the right side there is the available species
– On the bottom is the legend of the species
that are being shown in the top window
– The top shows the concentration of all the
species over time
IRGAS 100 Monitor Screen
Concentration of
species over time
Available
Species
IRGAS 100 System
Collecting a background
– After opening the program, pressing the start
button will automatically send the
spectrometer to collect a background and
then begin collecting a sample
Seeing the sample
– Clicking on the desired species tab at the top
will show you that species in real time
– That screen shows the fast concentration
tracker (FCT) and the averaged sample
IRGAS Configuration Manager
IRGAS Configuration Manager
IRGAS Configuration Manager
IRGAS Configuration Manager
IRGAS Configuration Manager
Data Retrieval
Data storage
– By default the data gets stored on the C drive
C:\Program Files\CIC Photonics\IRGAS
– IRGAS data
Quantification log
Spectral records
Quantification Log Folder
Data stored as a text file
Can be converted to an excel file
– Copy file, paste in the same folder, rename with an .xls
extension
In the excel file
Time
BMI
Species
Concen.
SE
FCT
SE-FCT
2nd Species
Concen.
SE
FCT
6/14/2005 14:21
3.17E-02
H2O
0
0.06
-0.16
0.06
CO2
0.011
0.013
0.011
Data storage names
– Folder with YY-MM
Folder with Quan YY-MM-DD.log
Spectral Records Folder
Stored with a .spc extension
– All market software writes and reads this format
This was created by Galatic, now ThermoGalactic
Data storage names
– Folder with YY-MM-DD
Absorbance File
– Abs YY-MM-DD HH:MM.zip
Background File
– Bck YY-MM-DD HH:MM.zip
Sample File
– Smp YY-MM-DD HH:MM.zip
Residual File
– Res YY-MM-DD HH:MM.zip
QMax
Using existing calibration file:
QMax
Quantification Set
Spectral Set
Calibrated Spectral Record of
specific molecule
Non-linear Behavior
As a rule of thumb a species behaves nonlinear when it is higher than 0.1 a.u.
The non-linear correction graph’s curve is
modeled by ax3+bx2+cx+d = 0
– In this equation the values that are necessary
to find are a, b, and c
– To do this non-linear correction there needs to
be at least 3 spectral records
In general when the residual curve is flat
line that indicates that there is non-linear
behavior
QMax
Starting a calibration from scratch:
IRGAS Spectra Reprocessing
IRGAS Spectra Reprocessing
Absorbance Data @ 1ppm/meter
0 .002 8
H2O
0 .002 6
NH3
0 .002 4
NO2
0 .002 2
SO2
0 .002 0
CO
NO
Absorbance
0 .001 8
0 .001 6
H2CO
CO2
0 .001 4
0 .001 2
0 .001 0
0 .000 8
0 .000 6
0 .000 4
0 .000 2
-0 .000 0
3 000
2 000
W ave num bers (c m-1 )
1 000
Software Installation
Software Installation
The installation window should
automatically pop-up
After the installation has been completed,
check that the computer and spectrometer
are communicating with each other
Establishing Communication
Network:
Instrument
Network
Computer
– Instrument address: 192.168.0.127
– Computer address: 192.168.0.YYY
Where YYY is any number between 0 and 225 that
is not 127
Establishing Communication
Two Ethernet configurations:
– Straight through
Instrument
Ethernet
Hub
Switch
Computer
– Crossover
Instrument
Computer
Ethernet Connection
Straight through configuration
1
2
3
4
5
6
7
8
1
2
3
4
5
6
7
8
Ethernet Connection
Crossover configuration
1
2
3
4
5
6
7
8
1
2
3
4
5
6
7
8
Verifying Communication
Changing network address
– Control panel
Network connection
– Local network
Properties
Last check for communication
– Control panel
ABB Bomem
Contact Information
(505) 343-1489
(505) 343-9520
TechSupport@cicp.com