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Last update: 2010-02-01
XRF Analysis of Glass Overview
of Samples
XRF
analysis of Green and Brown Glass
The analytical results shown here are by courtesy
of Mr. Theo W. Verkroost
of the Technical University, TU-Delft, The Netherlands.
On a regular basis, TU-Delft analyses a great
variety of glass samples including glass
with high Lead and/or Barium content. To enhance accuracy,
use is made of UniQuant’s
ability to firm up the calibration by one or more international
standards.
The procedure is to first copy UniQuant’s ‘universal’ calibration
data to a new folder
(sub-directory), for example named C:\UQ4\Glass. In these
data, the Kappa’s are firmed
up by one or more standards. In the example below, just one
standard is used, namely
European Standard Glass EC1.1, see last column.
Working with pressed powders has an advantage
here over working with flat glass discs.
A disc is cut for example from the bottom of a bottle assuming
that its composition is
representative for that one bottle as well as for an entire
batch of bottles (no segregation’s in
the process of making bottles). Powder on the other hand can
be made from pieces of
glass of one or several bottles which, when ground together,
ensures ‘representativity’.
Columns ‘XRF+UQ3’ show concentrations
found by a XRF + UniQuant 3. Glass No. 7
is treated as an unknown sample to compare results with certified
concentrations.
Columns ‘XRF’ show concentrations found
by a different lab using the conventional
calibration with several or many standards, where standards
and unknown samples
were presented as flat glass discs.
Clear glass Green glass Brown glass EC1.1
Glass No. 7 of used to refine
Society of Glass calibration
Technology
XRF+UQ3 XRF XRF+UQ3 XRF XRF+UQ3 XRF+UQ3
Cert. pressed glass pressed glass pressed pressed
Conc. powder disc powder disc powder powder
---------------- --------------- --------------- -------
SiO2 72.74 72.66 72.41 72.55 71.54 71.74 71.97
CaO 11.03 11.36 10.67 10.58 11.69 11.51 8.63
Na2O 13.90 13.46 12.40 12.29 12.42 12.38 13.41
Al2O3 1.50 1.50 1.63 1.70 1.57 1.65 1.08
MgO 0.14 0.14 1.45 1.47 1.63 1.65 3.78
Fe2O3 0.044 0.061 0.298 0.30 0.245 0.25 0.10
K2O 0.43 0.45 0.60 0.61 0.56 0.57 0.59
TiO2 0.042 0.039 0.047 0.052 0.062 0.069 0.04
Cr2O3 0.26 0.27 0.042 0.042
MnO 0.020 0.013 0.013 0.011
BaO 0.041 0.040 0.037 0.030
PbO 0.015 0.014 0.013 0.010
SO3 0.19 0.20 0.054 0.036 0.078 0.24
S 0.033
LOI(500°C) 0.07
Note:
UniQuant finds and automatically reports Sulphur as %SO3 in
Green glass and as %S in
Brown glass. The colour of brown glass is caused by Ferro-sulphide.
In production,
FeS2 may be added to the mixture. Carbon is used as a reduction
agent whilst Na2SO4 is
used a an oxidation agent. In the analysis shown above, UniQuant
has been set to treat
all S as SO3 or all S as S, depending on which of the two
has the largest concentration.
In principle, UniQuant can determine SO3
and S simultaneously. In fact, this feature is in
routine use at a cement plant, where Sulphur concentrations
are in the order of 1 mass%.
At Sulphur concentrations of 0.03% as in glass, simultaneous
determination is more difficult
and it is expected that a super-fine collimator is required
to improve resolution of SKa
from S and ‘SxKa’ from SO3. We intend to make a simple feasibility
study shortly and report
the results at this place. The topic is perhaps interesting
because technology of making
brown glass requires that reduction is not overdone. Presumably,
the ratio (S as SO3) / (S as S)
is about 80/20. There seems to be no easy and quick way to
determine this ratio.
Comments by E-mail are welcome
Same
Glass sample in 3 different forms
UniQuant1 (May 1989)
-------------------------------------------
Original 670mg
broken loose 1+33LiT Chemical
solid piece powder Bead spec.
------------ ------ ------- --------
MgO 1.6 ± 0.1 1.3 1.4 1.4
Al2O3 12.8 ± 0.3 11.7 12.6 14
SiO2 42.9 ± 0.5 39.9 43.2 43
CaO 34.1 ± 0.06 37.2 34.8 33
Fe2O3 1.8 ± 0.1 1.7 1.6 1.7
ZnO 0.4 ± 0.06 0.5 0.3 0.4
ZrO2 4.3 ± 0.2 4.6 4.5 4.5
BaO 0.3 ± 0.05 0.3 0.3 0.3
Boron
in Glass or Enamel
Most spectrometers can measure
the intensity of B Ka. The question is if it
is possible to determine the concentration of B2O3 on the
basis of the
B Ka intensity. The answer is not a simple YES or NO.
The problems are:
- the B Ka line is interfered by XRF lines from many elements
(30 or more).
- many of the interfering lines almost coincide with the B
Ka line.
- there is no spectral position at which the background of
B Ka can be
reliably measured because all positions in the vicinity
of B Ka are suspect
of being spectrally interfered.
-both background and line overlap corrections (expressed as
equivalent %B2O3)
are relatively high.
If a glass sample does not contain interfering elements at
levels higher than
say 0.1%, it may be quite feasible to determine B2O3 directly
by the B Ka intensity,
However,
in case one or more interfering elements are present at higher
levels,
corrections of B Ka for spectral line overlaps becomes doubtful.
This is
because the equivalent correction values (expressed as %B2O3)
are relatively
high. As a consequence, the B2O3 content would have to be
calculated from
the difference of large values. For example:
30% - (28% ± 3%) = 2%B2O3 ± 3%B2O3,
where the 28% ± 3% represents the total line overlap
correction.
Interfering elements are: Mo, Nb, Zr, Cl, Sb, Sn, Te, Hf,
Ru, Ag, Cd, In,
all Lanthanide elements (La...Lu), and many more.
There are 2 general solutions:
Solution 1
Determine B2O3 by a technique other than XRF and enter
its value
as known concentration in UniQuant.
Solution 2
Determine B2O3 as the non-measured rest from the difference
of the
sum of concentrations with 100%. This method works very well
with
UniQuant if 2 conditions are satisfied, namely:
- The Kappa's (Kii's) of the major elements must be very accurate.
When analysed with UniQuant, glass without B2O3 must
give a sum
of concentrations of 100 ± 0.5%, or better 100
± 0.3%.
- Samples must be measured as large flat glass specimen or
as beads.
This is in order to avoid 'shadow' effects as with powder
samples, which
would decrease the sum of concentrations.
Depending on the quality of calibration of the Kappa's, the
B2O3 content
calculated (as difference) may then be accurate to 0.3 to
0.5 weight%.
Below is an early example of 'Special Glass with High Boron',
for which no
special attention was given to the first condition mentioned
above.
Special
Glass with High Boron
Other (1991)
method UniQuant1
-------- ---------
La2O3 40.7 40.1
Y2O3 10.57 10.20
ZrO2 6.20 6.01
ZnO 4.53 4.70
SiO2 2.07 2.20
Gd2O3 2.0 2.7
Nb2O5 0.70
TiO2 0.11
Al2O3 0.04 0.04
P2O5 0.01 0.03
Fe2O3 0.01 0.01
B2O3 32.3 33.2*
------ ------
98.43 100.00
* Boron was not actually measured. Instead, it was specified
in UniQuant
that the non-measured rest is B2O3. The %B2O3 was then determined
by
difference, taking the absorption by B2O3 into account.
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