ASOMA
Application Note
®
PROCESS INSTRUMENTS
ASOMA PHOENIX II
Analysis of Titanium Dioxide & Zinc Oxide in Cosmetics
Introduction
Summary
This report demonstrates
the suitability of the
PHOENIX II Benchtop
XRF analyzer for use in the
quality control of titanium
dioxide and zinc oxide in
make-up, lotions and other
cosmetics products. It will
show that this data can be
used to make improvements
in product quality by
accurately and rapidly
determining the important
additive elements; i.e. TiO2
or ZnO, a key opacifying
agent used as sun block.
It can also be seen that
there is another advantage
in easily and quickly
measuring these element
during the production
process. Namely, by
ensuring that additive
package “over-dosing”
does not occur, significant
reductions in operational
costs can be achieved.
The PHOENIX II is an excellent QC benchtop analyzer that offers
a fast, precise, simple and non-destructive analysis technique well
suited for the analysis of TiO2 and ZnO in cosmetics products.
The PHOENIX II employs state-of-the-art optics. Indirect excitation
offers unique benefits because it eliminates most of the background
scatter emerging from the X-ray tube before it arrives at the sample.
This results in a dramatic improvement in peak-to-background signal,
especially in highly scattering materials. This translates to vastly
improved precision and lower detection limits than traditional direct
excitation XRF systems can achieve.
The PHOENIX II uses an onboard PC computer with a simple
touch screen interface. Thus, an external computer is not required.
Data handling and results storage can be obtained on a thermal
paper print out and are also stored in the hard drive of the PHOENIX
II. The data can be readily transferred to a USB thumb-drive or a
network Ethernet connection.
Calibrations are readily carried out using assayed standards. This
ensures easy traceability of results for quality purposes. This initial
calibration process is a “once only” procedure. Subsequently, the
curve can be restandardized, if required, by the touch of a button on
the main analysis screen.
The PHOENIX II offers power, versatility and performance all in a
small, compact, easy-to-use design.
These benefits work
together to maximize quality
and reduce operational
costs.
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Experimental Portion
XRF Sample Cup
Equipment
All measurements were conducted using a
PHOENIX II XRF analyzer. Performance is shown
for a measurement time of 100 seconds.
Sample Preparation
Each sample was stirred prior to analysis. A small
amount of lotion from each sample was then
transferred with a spatula into a commercially
available XRF sample cup. Care was taken to
ensure no air bubbles or air gaps were present at
the analysis surface.
Measurement Parameters
Easy assembly with film window
All measurement parameters are easily controlled
through the touch screen on the display panel.
Operators simply choose the correct method from
the analysis screen (there may be more than one
method stored, e.g. to deal with lotions or powders,
etc.) and then press the green ANALYZE button.
The results can be reported using a variety of
different options: results are reported on the display
screen; on a thermal paper printout; on an optional
external printer; and in the database history within
the analyzer.
Instrument Configuration
ASOMA PHOENIX II
Excitation: 48 kV 50 W Air-cooled X-ray Tube
Results for TiO2 in Makeup Tinted with Various
Levels of Fe2O3
Calibration for TiO2 in Makeup
Element: Ti
Std. Error of Estimate: 0.093
Units: % TiO2
RMS: 0.031
Detection: Gas-filled Proportional Counter
Sample
Given
Measured
Analyte Optimization: X-ray voltage, current and
X-ray filters
1
12.18
12.090
2
11.01
11.200
Atmosphere: Air
3
9.34
9.321
4
8.84
8.763
Options: Secondary target; Polypropylene 6 µm
film
Note: No consumable gases required.
2
5
6.34
6.308
6
5.34
5.267
7
4.34
4.357
8
10.18
10.118
9
7.17
7.306
12
11
Measured ( % )
10
9
8
Similarly, if both titanium and iron oxides need
to be quantified as pigments for color balance,
that is easily performed using PHOENIX II for both
elements, with comparable performance as shown
for titanium dioxide.
7
6
5
4
4
5
6
7
8
9
10
11
12
Given ( % )
Results for ZnO in Lotion
Precision for TiO2 in Makeup
10 repeat analyses at 100 seconds per
measurement
Element: TiO2
Calibration for ZnO in Lotion
Units: %
Element: Zn
Std. Error of Estimate: 0.018
Units: % ZnO
RMS: 0.007
Sample
Given
Measured
1
0.50
0.504
Sample
Given
Mean
Std.
Dev.
% Rel.
2
1.00
0.975
7
4.34
4.349
0.008
0.19
3
1.50
1.525
4
8.84
8.773
0.016
0.19
4
2.00
2.006
1
12.18
12.051
0.029
0.24
5
2.50
2.479
6
3.00
3.008
Minimum Detection Limit (MDL)
TiO2 in Makeup
Correlation Plot
3.0
2.5
Measured ( % )
The Minimum Detection Limit (MDL) for an element
is determined as three times the standard deviation
of ten analyses of a blank Teflon sample. The
following MDL was derived using this empirical
method and applies to this matrix and concentration
range.
3.5
2.0
1.5
Element
Count Time
MDL
1.0
Ti
100 sec
0.007 % TiO2
0.5
The results shown are based on using an assayed
suite of calibration standards of actual product
provided by a current user, and are typical of results
3
0.0
0.0
0.5
1.0
1.5
2.0
Given ( % )
2.5
3.0
3.5
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achievable for these types of applications. Both
the titanium and iron are easily measured. In this
case, the iron did not need to be controlled and so
was measured only to compensate for its effects on
the titanium measurement. If provided with assay
values for the iron oxide, comparable concentration
results can be achieved for iron oxide as those
shown for the titanium dioxide.
Correlation Plot
Analysis of Titanium Dioxide & Zinc Oxide in Cosmetics
Units: %
Sample
Given
Mean
Std.
Dev.
% Rel.
1
0.50
0.499
0.002
0.42
3
1.50
1.522
0.006
0.38
6
3.0
3.028
0.009
0.29
Minimum Detection Limit (MDL)
ZnO in Lotion
The Minimum Detection Limit (MDL) for an element
is determined as three times the standard deviation
of ten analyses of a base lotion sample, containing
no ZnO. The following MDL was derived using this
empirical method and applies to this matrix and
concentration range.
Element
Count Time
MDL
Zn
100 sec
0.005% ZnO
The results shown are based on using an assayed
suite of calibration standards of actual product
provided by a current user, and are typical of
results achievable for these types of applications.
All three elements can be present together (Ti,
Fe and Zn) and PHOENIX II will give comparable
performance as shown in this report.
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All rights reserved. Printed in the U.S.A.
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One of a family of innovative process analyzer solutions from AMETEK Process Instruments.
Specifications subject to change without notice.
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Element: ZnO
As can be seen from the above data, the use
of the PHOENIX II XRF system gives excellent
performance when applied to the determination of
titanium or zinc oxides in cosmetics. Results are
rapid, precise and analysis is easily carried out,
even by non-laboratory personnel. Because no
consumable chemicals are used, the relative ”cost
of ownership“ is much lower than other analytical
techniques.
Application Note
Conclusion
Precision for ZnO in Lotion
10 repeat analyses at 100 seconds per
measurement