contrAA® A Revolution in Spectroscopy
Basics and Applications of High-Resolution Continuum Source AAS
Methods for element analysis
AAS – a well established method for more than 50 years

Simplicity

Single element method

Less interferences

Specific HCLs required

Robustness

Unprofitable for many elements

Low purchase cost

Limitation in background correction

Low operation cost
contrAA® - A Revolution in Spectroscopy
BUT !!
2
New instrument development needs motivation
AAS goes multielement!
contrAA® - A Revolution in Spectroscopy
3
New instrument development needs motivation:
We expect fast results
LS AAS
Cx
Cu
Pb
Fe
Cd
Ni
Zn
Single element method
contrAA® - A Revolution in Spectroscopy
4
New instrument development needs motivation:
We expect fast results
Real multielement Analysis
CS AAS
Cu, Pb, Fe, Cd,
Ni, Zn…
Sequential multi element analysis
contrAA® - A Revolution in Spectroscopy
5
New instrument development needs motivation
We need more information!
Background correction
failed, but why???
In case of a spectral interference, we can see only the result, but not the
reason – therefore the optimization of method parameters to avoid the
spectral interferences is difficult.
contrAA® - A Revolution in Spectroscopy
6
Key components of HR-CS AAS
HR-CS AAS
LS-AAS
Radiation source
Xenon – short arc lamp
HCL, EDL, boosted HCL
Atomizer
Identical atomizer for flame and graphite technique
Monochromator
High resolution >1:140000
Low resolution
Detector
CCD array detector
Single spot detector (PMT)
Software
ASpectCS ®
contrAA® - A Revolution in Spectroscopy
WinAAS®
7
 Optical set up CS AAS
Furnace
Flame
CCD detector
Echelle grating
Arc lamp
prism
High Resolution
Monochromator
ISAS Berlin
 High spectral resolution: / Δ > 145 000
contrAA® - A Revolution in Spectroscopy
 Low focal length: f  400 mm
8
Radiation source

LS AAS
Hollow cathode lamp (HCL)
line radiator
Cathode contains the element
to be analyzed
contrAA® - A Revolution in Spectroscopy

HR-CS AAS
Xenon short arc lamp continuum
radiator
Covers whole wave length range
185 – 900 nm
Determination of more than 67
elements with one lamp only
9
Radiation source
Different radiation sources in comparison
100
1
2
R adiance [W / cm sr nm ]
10
Ag
Pb
0 .1
A
B
C
Au
0 .0 1
As
Zn
Pb Cd
1 E -3
200
250
300
350
400
W a v e le n g th [n m ]
Source: „High-resolution continuum source AAS“ Welz,Becker-Roß,Florek,Heitmann
A Xenon-short arc lamp, XBO 301, 300 W, (GLE Berlin), „Hot - Spot“ - Mode
B Xenon lamp, L 2479, 300 W, (HAMAMATSU), diffuse mode
C D2 - Lamp, MDO 620, 30 W, (HERAEUS)
contrAA® - A Revolution in Spectroscopy
10
Atomizer in HR-CS AAS
Flame atomizer
contrAA® - A Revolution in Spectroscopy
Graphite furnace atomizer Quartz cell atomizer
11
Double Echelle Monochromator
6
1
4
3
5
1: entrance slit (fixed)
2: off-axis parabolic mirror
3: prism in Littrow- position
4: intermediate slit (variable)
2
2
5: Echelle- grating in Littrowposition
6: CCD – array detector
Source: ISAS Berlin
contrAA® - A Revolution in Spectroscopy
12
Monochromator resolution LS AAS vers. HR-CS AAS
LS AAS
Emission scan
Mn – Triplet:
279.4817 nm
279.8269 nm
280.1085 nm
CS AAS
Absorption spectra
Resolution factor 100
better than LS AAS !!!
contrAA® - A Revolution in Spectroscopy
13
High Resolution – spectral interferences
Analyte
Wavelength (nm)
Disturbing
elements
Wavelength
(nm)
-Difference
(pm)
Se
196.03
Fe
196.060
30
As
193.70
Fe
193.670
30
Zn
213.856
Fe
213.859
3
Cd
228.80
As
228.810
10
Fe
228.720
80
Ni
232.003
Fe
232.036
33
Sn
224.605
Pb
224.690
85
Fe
224.565
40
Mn
279.48
Fe
279.470
10
Cu
324.75
Fe
324.600
15
Al
396.15
Fe
396.110
40
contrAA® - A Revolution in Spectroscopy
14
CCD Detector
New detection technology
Detector “Pixels” are illuminated
and read out simultaneously and
independently.
200 Pixels are used analytically
200 independent detectors !
3 Pixels for AA measurement
- and the others???
contrAA® - A Revolution in Spectroscopy
15
Corrections
Type of interference
LS-AAS
HR-CS AAS
Lamp intensity drift
Optical double beam
sequential
Reference pixels
simultaneous
Thermal emission
Lamp modulation
sequential
Reference pixels
simultaneous
Non specific absorption
BG correction
sequential
Reference pixels
reference spectrum
simultaneous
contrAA® - A Revolution in Spectroscopy
16
Corrections
In HR-CS AAS we have a Third Dimension, i.e. we can see a lot more !
 We can see the spectral
interference
 We can avoid the spectral
interference
 And we have much better
ways to correct for spectral
interferences
contrAA® - A Revolution in Spectroscopy
17
contrAA® - A Revolution in Spectroscopy
V 318.540
Fe 318.490
Ni 318.437
V 318.341
Background correction and resolution
18
Corrections of discontinuous events
Diatomic molecules with rotational fine structure

OH, NO, CN are natural constituents of flame gases

NO, PO, SiO, CS etc. might be generated in the presence of high
matrix concentration

Neither the D2 nor the Smith-Hieftje system can correct for this
background,

the Zeeman system can only correct if the background is not affected
by the magnetic field !

In HR-CS AAS we can measure and store a reference spectrum that
can be subtracted from the sample spectrum using a least-squares
algorithm
contrAA® - A Revolution in Spectroscopy
19
A Short Glance on Correction Models
“Least Squares Background Correction”
contrAA® - A Revolution in Spectroscopy
20
Corrections of discontinuous events - Recording of reference
spectra
NO- Structure on Zn- line 213.857 nm
blank: 1% HNO3
contrAA® - A Revolution in Spectroscopy
1% HNO3 + 0.05 mg/L Zn
21
Corrections of discontinuous events - Recording of reference
spectra
Correction of NO structure at 213.857 nm Zn- line
NO structures corrected Zn absorption spectra
contrAA® - A Revolution in Spectroscopy
22
Quality is the difference
contrAA® - A Revolution in Spectroscopy
23
Thank you for your attention!
contrAA® - A Revolution in Spectroscopy
24