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Short Application HR-CS SS GF MAS
Determination of fluorine in silicon nitride
Experimental
Sample preparation
The silicon nitride powder to be examined was analyzed directly using the direct solid technology,
without further preparation of the sample.
Determination
The measurements were carried out using the contrAA High-Resolution Continuum Source
Graphite Tube AAS and the solid autosampler SSA600L, which is equipped with a liquid dosing
unit. The determination of the fluorine concentration was performed via molecule absorption of
gallium monofluoride. To create GaF, 10 g/L Ga-(III)-nitrate hydrate (Sigma-Aldrich) is used as
molecular formation reagent in water. A solid graphite tube was used as the graphite tube. The
graphite autosamplers were permanently coated with Zr (1g/L Zr) before the analytical usage. To
stabilize the analyte fluorine and the molecular formation reagent Ga during drying and pyrolysis,
a Pd/Mg/Zr modifier (0.1%/0.05%/20 mg/L Pd/Mg/Zr) as well as a 10 g/L NaAc modifier was used
in water. The Pd/Mg/Zr modifier was pretreated thermally at 1200°C with the major part of the
molecular formation reagent Ga (NO3)3 to activate the Pd. Under these conditions a pyrolysis
temperature for the samples of 600℃ and a molecular formation temperature of 1,600℃ were
used. As the sample has a relatively high concentration of fluorine in the ppm area, the most
sensitive molecule absorption line of GaF was not used. The wavelength of 209.419 allows a
fluorine calibration in the concentration range of 100–500 ppm F in a solid with a sample weight
of approx. 0.5 mg.
Method parameters
Element
Wave
lengt
h
T Pyr.
T Atom.
Ramp
[°C]
[°C]
[°C/s]
Tube
type
Modifier
Thermal
pretreatment
[nm]
F (GaF)
209,4
19
600
1600
1500
Determination of fluorine in silicon nitride
CSMA_SS_01_12_e | 01/ 2012
Solid
10 µL 0.1%/0.05%/20
mg/L Pd/Mg/Zr
yes
10 µL 10 g/L Ga(NO3)3
yes
5 µL 10 g/L NaAc
5 µL 10 g/L Ga(NO3)3
no
no
Evaluation parameters
Element
Ev.pixel
F (GaF)
5
Test
time
Spectral observation
width
[s]
[nm]
5,0
0,23
Temperature-time program:
Determination of fluorine in silicon nitride
CSMA_SS_01_12_e | 01/ 2012
Background correction
[Pixel]
200
IBC
Standard calibration:
Liquid calibration standards
Automatic creation of standards by SSA600L with liquid dosing unit
Calibration standards 50/ 100/ 150/ 200/ 250 ng in graphite tube (from stock solution 10 mg/L F
in H2O)
3 measurements per calibration statistic, 6 measurements per solid sample
Temporal peak area integration via 5 spectral pixels
Linear calibration curve:
Element
F (GaF) 209.419 nm
R² =
0.9998
Element
F (GaF) 209.419 nm
Standard 4: 200 ng F
Signal
profile
blue: Analyte signal
Determination of fluorine in silicon nitride
CSMA_SS_01_12_e | 01/ 2012
Si3N4
Spectral
vicinity
3D
spectra
Results
Element fluorine
Sample
Sample weight
F concentration
mg/kg
RSD
in %
Si3N4
0.14 – 0.60 mg
530 ± 6,0
7,0
QC standard 4
(200 ng F)
CRM NCS DC
73325 (base)
certified: 321 ± 29
206 ng F
0.18 – 0.60 mg
(292 – 350 mg/Kg)
Determination of fluorine in silicon nitride
CSMA_SS_01_12_e | 01/ 2012
302 ± 3,0
Recovery rate
%
3,1
103
5,6
94,1
Summary
With the use of a Xe short arc lamp as a lamp continuum source in the HR-CS AAS all absorption
lines in the spectral range of 185–900 nm are available for analytical evaluation. This is also the
prerequisite for the analytical use of molecule absorptions with a random wave length. This
makes it possible for the first time to use fine-structured molecule absorption spectra as gallium
mono fluoride for the analytical determination of non-metals as in this case for fluorine.
CCD array is used as detector, which guarantees a simultaneous and powerful background
correction and offers additional spectral information for the analysis line to be examined by the
simultaneous readout of 200 detector pixels. Thanks to the innovative simultaneous background
correction spectral interferences can be corrected on the analyte or molecule line regardless of
the wavelength.
Additional information about the sample is automatically retained by the visualization of the
simultaneously recorded spectral environment around the analyte wave length. Method
development and method optimization thus becomes much easier than with the classic AAS.
Using the procedure presented it is possible to determine fluorine in the silicon nitride matrix
without any problems from the direct solid sample, without further sample preparation. The
calibration is performed with aqueous fluoride standards. The measurement of an aqueous
quality control standard after the Si3N4 sample shows a very good recovery rate of 103%. The
same sample platforms are used for this QC determination as for determining fluoride in niobium
pentoxide. For this reason, it is possible to suggest that the silicon nitride matrix has a small
matrix influence on the fluoride concentration determination with HR-CS MAS. To safeguard a
more accurate concentration result, we recommend comparing the determination of the fluoride
concentration after melt digestion or calibration with a certified reference material for fluoride in a
similar matrix. Unfortunately, neither option is available here in the lab. Alternatively, a base
(silicate matrix), in which fluoride is certified, is examined using this method. The fluoride
concentration lies within the certified range and a recovery of the average value of 94% thus
confirms that the fluoride concentration determined in the silicon nitride is correct.
Chemicals provided by Sigma Aldrich® were used.
The generated data may be re-used by Analytik Jena.
Printout and further use permitted with reference to the source.
© 2012 Analytik Jena AG
Publisher:
Analytik Jena AG
Konrad-Zuse-Straße 1
07745 Jena
Phone +49 (0) 36 41 / 77-70
Fax +49 36 41 77-92 79
Determination of fluorine in silicon nitride
CSMA_SS_01_12_e | 01/ 2012
www.analytik-jena.com
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