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Application note HR-CS SS GF MAS
Determination of fluorine in copper concentrate
Introduction
The demand of copper in the electronics industry has greatly increased in the last couple of years.
Due to the fact that the supply of this metal still falls well short of demand, copper prices are rising
worldwide.
Copper concentrate is the first commercial product of the copper production line and comprises of
copper, iron and sulfides. It is the raw material for copper smelters that produce metallic copper,
anode or blister copper and high fluorine contents hamper their processing. Yet, fluorine is present
in a variety of rock minerals, such as fluorite (CaF2) and fluorapatite (Ca5 (PO4)3FOH). Besides,
fluorine can also occur dispersed throughout mineral species as a replacement ion or displacement
anion. The presence of more than 1000 ppm fluorine affects the sulfuric acid units of copper
smelters. Thus, price penalties are normally applied to copper concentrates with high fluorine
contents.
Determination
Fluorine contents in samples of copper concentrate were determined by graphite furnace AAS
using the High-Resolution Continuum Source technology along with the solid sampler SSA 600L
equipped with a liquid dosing unit. Finely ground ore samples were provided by the customer and
used as received without further sample treatment.
The fluorine concentration was determined indirectly by evaluating the molecular absorption of
indium monofluoride (InF), into which fluorine was converted stoichiometrically. Aqueous indium(III)-nitrate hydrate solutions (Merck) were used as molecule forming reagent yielding a finestructured molecule absorption spectra of indium monofluoride. Graphite sample carriers were
permanently coated with tungsten (1 g/L (NH4)2WO4) prior to fluorine analysis. Pd (0.1%) and Al
(0.1%) were used as modifiers to stabilize fluoride during drying and pyrolysis. Measurements
were performed using a pyrolysis temperature of 500 °C and a molecule forming temperature of
2000 °C. The InF signal was analyzed by time peak area integration over 6 spectral pixels (pixel
99-105).
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Method parameters
Element
Wavelength
[nm]
F (InF)
solid
mode
234.718
T Pyr.
T Atom.
Ramp
[°C]
[°C]
[°C/s]
500
2000
1000
Tube
type
Solid
Thermal
modifier
pretreatment
Modifier
5 µL 1 g/L Pd as nitrate
3 µL 1 g/L Al as nitrate
7 µL 1 g/L In as nitrate
no
no
no
Evaluation parameters
Element
F (InF)
Eval.-
Readtime
pixel
6
Spectral observation
width
[s]
[nm]
[Pixel]
5.2
0.26
200
Background correction
IBC-m
Temperatur time program:
It was found that utilizing the molecular absorption of InF, the oven program is significantly shorter
than when using the alternative GaF lines (e.g. 212.111 nm, 209.419 nm and 213.794 nm) for
fluorine analysis. That is because GaF analysis requires more elaborate pre-treatment of the
sample carriers.
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Calibration:
Non-linear calibration curve:
Element
F (InF) 234.718 nm
R² = 0.985
Element
F (InF) 234.718 nm
Copper concentrate A 300 g/t (weight 0.47 mg, mass 0.141 µg F)
Signal plot
blue: analyte signal
A 10 point calibration curve for fluorine concentrations from 50 to 2200 ppm F was obtained using
an internally certified copper concentrate of 300 g/t F. By varying the sample weights from approx.
0.1-0.75 mg, fluorine contents from 50 to 2200 ppm were realized, respectively. This calibration
range is reasonable, since most of the copper concentrate samples submitted to the analysis were
within this range. A 300 was re-determined after the calibration (QC-standard) recovering a
concentration of 297 g/t (99%).
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Element
F (GaF) 234.718 nm
Sample A P1
Spectral
environment
3D-spectrum
Results
Sample
Mode
F- conc.
in g/t
RSD in %
Target F-conc.
in g/t
A 38
solid
52 ± 7.7
12.4
38
A 90
solid
92 ± 7.5
12.4
90
A 110
solid
100 ± 7.4
18.7
110
A 160
solid
174 ± 7.5
9.7
160
A 300
solid
297 ± 8.6
17.0
300
A P1
solid
53 ± 8.4
13.9
not available
A P2
solid
319 ± 8.5
8.0
not available
Five replicate measurements were used to determine the fluorine content of the copper
concentrates. Samples containing higher F-contents, i.e. samples whose absorbance values are
beyond the calibration range, can be measured by reducing the sample weights. Likewise,
concentrations that are below the calibration range can be measured easily by increasing the
sample weight. However, the detection limit estimated from the slope of the calibration curve
(calibration method) was found to be about 1 ppm F; however, a sample of this low F-content was
not available.
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Summary
Using the Xe short arc lamp as a continuum source in the HR-CS AAS all absorption lines in the
spectral range of 185-900 nm are available for analytical evaluation allowing the determination of
non-metals such as fluorine by molecule absorption spectroscopy. Measurements were performed
using indium(III) nitrate hydrate as molecule forming reagent as well as Pd and Al modifiers. The
resulting fine-structured molecule absorption spectra of indium mono fluoride were observed at a
wavelength of 234.718 nm.
The determination of fluorine in the inorganic matrix of the copper concentrate is feasible without
further sample preparation in a range from 50 to 2200 ppm. The calibration was performed with a
solid copper concentrate of known fluorine content (no reference material). Moreover, a QCstandard recovery rate of 99% was obtained proving the applicability of the method. The fluorine
content of seven copper concentrate samples in the range from 50 to 320 ppm was determined.
They are in good agreement with the certified/expected concentrations.
Chemicals were purchased from Sigma Aldrich®.
Printout and further use permitted with reference to the source.
© 2013 Analytik Jena AG
Publisher:
Analytik Jena AG
Konrad-Zuse-Straße 1
07745 Jena, Germany
Phone +49 (0) 36 41 / 77-70
Fax +49 (0) 36 41 77-92 79
Determination of fluorine in copper concentrate
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