Analysis of Silicone Oils by High Performance
Liquid Chromatography and Corona Charged
Aerosol Detection
Marc Plante, Bruce Bailey, Ian N. Acworth
Thermo Fisher Scientific, Chelmsford, MA, USA
Overview
Purpose: To develop HPLC methods for both the detailed,
characterization of silicone oils and for rapid quantitation of silicone
oils in samples using an HPLC system with a charged aerosol
detector.
Methods: Two methods, one qualitative for characterization and one
quantitative using a solid core C18 column, are outlined.
Results: Different silicone oils were characterized using the
qualitative method; silicone oils in commercial products were
measured, with a quantitation limit of approximately 100 ng on
column.
Introduction
Silicone oils are unique materials with multitudes of significant uses in
our modern world. Silicone-based materials are thermally stable,
relatively inert, and are generally non-toxic, making them useful as
oils and greases, lubricants, anti-foaming agents, and coatings.
Silicone oils are often used in electronics, hydraulic systems, and
many consumer products. The measurement of silicone oils is
complicated by their solubility properties, their variations in basic
structure including a wide variety of chemical moieties that may be
part of this structure, as well as their general lack of chromophores
making detection by ultraviolet absorption impractical.
The charged aerosol detector is a sensitive, mass-based detector,
especially well-suited for the determination of any nonvolatile analyte
independent of chemical characteristics. As shown in Figure 1, the
detector uses nebulization to create aerosol droplets. The mobile
phase evaporates in the drying tube, leaving analyte particles, which
become charged in the mixing chamber. The charge is then measured
by a highly sensitive electrometer, providing reproducible, nanogramlevel sensitivity. This technology has greater sensitivity and precision
than ELSD and refractive index (RI), is gradient compatible and is
simpler to operate than a mass spectrometer (MS). Compounds do
not have to possess a chromophore (unlike UV detection) or be
ionized (as with MS).
Two charged aerosol detection methods were developed: one to
characterize the individual components of silicone oils, and the other
to provide quantitation of a near single peak of silicone oil to 100ng
(o.c.). The characterization method used the Thermo Scientific™
Dionex™ UltiMate™ 3000 RS system, and the quantitation method
used an UltiMate 3000 SD system in normal phase. Both methods
used a solid core C18 column and the Thermo Scientific™ Dionex™
Corona™ ultra RS™ charged aerosol detector.
Liquid Chromatography –Quantitation
HPLC System:
Thermo Scientific™
LPG-3400SD pump
and TCC-3000RS c
HPLC Column:
Accucore 2.6 µm C
Column Temp.:
40 °C
Mobile Phase A:
0.5% Formic acid/a
(35:35:30), helium s
Mobile Phase B:
Tetrahydrofuran*, h
Flow Rate:
0.3–1.0 mL/min
Injection Volume:
2–10 µL
Detector:
Corona ultra RS
Nebulizer Temp.:
10 °C
Filter:
6
Data Rate:
10 Hz
Power Function:
2
Flow Gradient for Quantitation:
Time (min)
Flow Rate
(mL/min)
%A
%B
-5.0
0.6
100
0
-0.2
0.6
100
0
0.3
100
0
0.0
0.3
100
0
0.5
0.6
100
0
-0.1
Tim
*No BHT added.
Data Analysis
All HPLC chromatograms were obtained
Scientific™ Dionex™ Chromeleon™ Ch
software, 7.1 SR 1.
Results
Sample Analysis
To investigate relative responses of diffe
silicone oil samples were characterized
with different viscosities (200 cP and 100
used as a heating bath oil. From the ove
in Figure 2, the 1000 cP oil sample is co
larger molecular weight polysiloxanes (la
sample, as characterized by the bulk of p
times. The heating bath oil is comprised
chain groups, as identified by over 170 d
least partially resolved for this oil.
FIGURE 2. Characterization of three d
(blue) and 1000 cP (black) viscosities
silicone oil (pink)
The combination of these chromatographic methods with the
capabilities of the charged aerosol detection provides unique
opportunities for detailed characterization of a silicone oil sample, as
well as quantitation of silicone oil-containing samples.
FIGURE 1. Schematic and Functioning of Charged Aerosol
Detection
1
10
3
Retention time precision was demonstra
heating bath silicone oil sample (Figure
systems, controlled by the Chromeleon s
injections to be synchronized with the pu
and matching system conditions for each
standard deviation for retention time at 5
2
.
8
4
6
5
9
7
Methods
1.
2.
3.
4.
5.
6.
7.
Liquid eluent enters from HPLC system
Pneumatic nebulization occurs
Small droplets enter drying tube
Large droplets exit to drain
Dried particles enter mixing chamber
Gas stream passes over corona needle
Charged gas collides with particles and
charge is transferred
8. High mobility species are removed
9. Charge is measured by a highly sensitive
electrometer
10.Signal transferred to chromatographic
software
Sample Preparation - Characterization
Samples of silicone oil were dissolved in chloroform, at a
concentration of approximately 40 mg/mL.
2 Analysis of Silicone Oils by High Performance Liquid Chromatography and Corona Charged Aerosol Detection
Liquid Chromatography – Characterization
HPLC System:
Thermo Scientific™ Dionex™ UltiMate™ 3000
FIGURE 3. Overlays of three separate
bath silicone oil sample. Only the 50 t
total run (inset) is shown for clarity.
17.4
17.0
pA
16.0
15.0
14.0
13.0
12.0
11.0
10.0
9.0
8.0
7.0
6.0
5.5
49.48
50.00
50.50
51.00
51.50
52.00
52.50
A silicone-based topical product used fo
7. Charged gas collides with particles and
charge is transferred
8. High mobility species are removed
9. Charge is measured by a highly sensitive
electrometer
10.Signal transferred to chromatographic
software
Methods
15.0
14.0
13.0
12.0
11.0
10.0
9.0
Sample Preparation - Characterization
8.0
7.0
Samples of silicone oil were dissolved in chloroform, at a
concentration of approximately 40 mg/mL.
6.0
5.5
Liquid Chromatography – Characterization
HPLC System:
Thermo Scientific™ Dionex™ UltiMate™ 3000
DGP-3600RS pump, WPS-3000RS autosampler,
and TCC-3000RS column oven
HPLC Column:
Thermo Scientific™ Accucore™ 2.6 µm C18,
3.0 × 150 mm
Column Temp.:
40 °C
Mobile Phase A:
Methanol
Mobile Phase B:
n-Propanol
Flow Rate:
0.5 mL/min
Injection Volume:
2–10 µL
Sample:
38 mg/mL silicone oil in chloroform
Detector:
Corona ultra RS
Nebulizer Temp.:
10 °C
Filter:
5
Data Rate:
10 Hz
Power Function:
1.00
Flow Gradient for Characterization:
49.48
50.00
50.50
51.00
51.50
52.00
52.50
53.0
A silicone-based topical product used for com
characterized using this method, as shown b
Figure 4. The material appears to contain a
smaller molecular weight polysiloxanes mixe
molecular weight polysiloxanes that elute at
FIGURE 4. HPLC chromatogram of a silic
product. Product appears to be made of h
polysiloxane (85 minutes) mixed with mo
molecular weight polysiloxanes. The inse
moderate molecular weight regions.
80.0
pA
18.0
70.0
pA
16.0
14.0
60.0
12.0
10.0
50.0
8.0
6.0
40.0
4.0
2.0
30.0
0.0
-2.0
20.0
Time (min)
%A
%B
Curve
-10
100
10
5
0.0
0
100
10
5
-10.0
80
15
85
3
85
0
100
5
0.0
10.0
20.0
30.0
40.0
50.0
10.0
f Silicone Oils by High Performance Liquid Chromatography an
harged Aerosol Detection
0
100
5
100
0
5
100
100
0
5
Bruce Bailey, Ian N. Acworth
Sample and Standard Preparations - Quantitation
SamplesUSA
containing silicone oil were dissolved in tetrahydrofuran, at a
r Scientific, Chelmsford, MA,
product concentration of 10—20 mg/mL and centrifuged at 10,000 g for
ethods for both the detailed,
s and for rapid quantitation of silicone
C system with a charged aerosol
qualitative for characterization and one
C18 column, are outlined.
were characterized using the
s in commercial products were
limit of approximately 100 ng on
als with multitudes of significant uses in
sed materials are thermally stable,
ally non-toxic, making them useful as
nti-foaming agents, and coatings.
electronics, hydraulic systems, and
e measurement of silicone oils is
properties, their variations in basic
ety of chemical moieties that may be
s their general lack of chromophores
t absorption impractical.
is a sensitive, mass-based detector,
etermination of any nonvolatile analyte
acteristics. As shown in Figure 1, the
create aerosol droplets. The mobile
g tube, leaving analyte particles, which
chamber. The charge is then measured
eter, providing reproducible, nanogramgy has greater sensitivity and precision
x (RI), is gradient compatible and is
s spectrometer (MS). Compounds do
phore (unlike UV detection) or be
3 minutes. HPLC sample vials were filled with the supernatant.
Standards (Silicone oil 1000 cP) were prepared by dissolving 10
mg/mL of silicone oil in tetrahydrofuran, diluted to 1 mg/mL and then
sequentially diluted to lower concentrations.
Liquid Chromatography –Quantitation
HPLC System:
Thermo Scientific™ Dionex™ UltiMate™ 3000
LPG-3400SD pump, WPS-3000RS autosampler,
and
TCC-3000RS column oven
HPLC Column:
Accucore 2.6 µm C18, 3.0 × 150 mm
Column Temp.:
40 °C
Mobile Phase A:
0.5% Formic acid/acetonitrile/tetrahydrofuran*
(35:35:30), helium sparge
Mobile Phase B:
Tetrahydrofuran*, helium sparge
Flow Rate:
0.3–1.0 mL/min
Injection Volume:
2–10 µL
Detector:
Corona ultra RS
Nebulizer Temp.:
10 °C
Filter:
6
Data Rate:
10 Hz
Power Function:
2
Flow Gradient for Quantitation:
Time (min)
Flow Rate
(mL/min)
%A
%B
Time (min)
0.6
100
0
Flow Rate
(mL/min)
%A
-5.0
4.0
0.6
100
0
-0.2
0.6
100
0
6.0
0.6
0
100
-0.1
%B
0.3
100
0
8.0
0.6
0
100
0.0
0.3
100
0
10.0
1.0
0
100
0.5
0.6
100
0
12.0
1.0
50
50
14.0
0.6
100
100
*No BHT added.
Data Analysis
All HPLC chromatograms were obtained and compiled using Thermo
Scientific™ Dionex™ Chromeleon™ Chromatography Data Station
software, 7.1 SR 1.
Results
Sample Analysis
5
10
15
20
25
30
35
40
45
50
55
6
The method provides a high-resolution HPLC
detailed characterization of polysiloxane ma
the solid core column in this method achieve
theoretical plates and therefore, the high lev
these figures. The charged aerosol detector
and consistent response for these analytes.
The near-consistent response of charged ae
volatile analytes enables the quantitation of t
samples used above. The second method, s
quantitation, uses an aqueous acetonitrile m
tetrahydrofuran gradient to elute the analyte
rapid manner, yielding a near-single peak. C
subtraction is used to remove baseline devia
rapid gradient.
This quantitative method was evaluated using
the 1000 cP silicone oil standards, a calibration
78 to 10,000 ng o.c., as shown in Figure 5. Sys
acceptable, with peak area percent relative sta
(10,000 ng o.c.) to 7.28 (156 ng o.c.). The quan
approximately 100 ng o.c, based on a signal to
Samples that were tested included a 200 cP si
oil, and three consumer products, including a s
and a gas relief product containing different for
oil and the heating bath oil were also used to g
calibration curves to investigate their response
1000 cP oil standard. These results are in Tabl
The 200 cP oil showed essentially equal respo
oil, but the heating bath oil differed in response
in this comparison. This may be associated wit
groups or numbers of associated groups conta
it is recommended that the silicone oil calibratio
at least similar) to the silicone that is to be quan
there is a clear difference between the 200 and
heating bath oil silicone.
FIGURE 5. Silicone oil calibration curves, fr
in triplicate, 2000 to 10,000 ng o.c. (200 cP a
12
10
Peak Area (pA*min)
95
95
0
8
6
4
To investigate relative responses of different oils, three different
2
silicone oil samples were characterized consisting of two similar oils
with different viscosities (200 cP and 1000 cP) and a third oil that is
• PN70538_e 06/13S
Thermo Scientific Poster Note
3
0
0
2000
4000
6000
8000
used as a heating bath oil. From the overlay of chromatograms shown
Amount (ng o.c.)
in Figure 2, the 1000 cP oil sample is comprised of a greater amount of
100
ection methods were developed: one to
al components of silicone oils, and the other
a near single peak of silicone oil to 100ng
on method used the Thermo Scientific™
0 RS system, and the quantitation method
D system in normal phase. Both methods
umn and the Thermo Scientific™ Dionex™
rged aerosol detector.
All HPLC chromatograms were obtained and compiled using Thermo
Scientific™ Dionex™ Chromeleon™ Chromatography Data Station
software, 7.1 SR 1.
Sample Analysis
To investigate relative responses of different oils, three different
silicone oil samples were characterized consisting of two similar oils
with different viscosities (200 cP and 1000 cP) and a third oil that is
used as a heating bath oil. From the overlay of chromatograms shown
in Figure 2, the 1000 cP oil sample is comprised of a greater amount of
larger molecular weight polysiloxanes (later elution) than the 200 cP oil
sample, as characterized by the bulk of peak area at higher retention
times. The heating bath oil is comprised of more isolable polysiloxane
chain groups, as identified by over 170 different peaks that were at
least partially resolved for this oil.
Retention time precision was demonstrated by repetitive analysis of the
heating bath silicone oil sample (Figure 3). The UltiMate 3000 LC
systems, controlled by the Chromeleon software, enables sample
injections to be synchronized with the pump delivery, allowing for exact
and matching system conditions for each injection. The percent relative
standard deviation for retention time at 50 minutes was 0.02%.
Liquid eluent enters from HPLC system
Pneumatic nebulization occurs
Small droplets enter drying tube
Large droplets exit to drain
Dried particles enter mixing chamber
Gas stream passes over corona needle
Charged gas collides with particles and
charge is transferred
8. High mobility species are removed
9. Charge is measured by a highly sensitive
electrometer
10.Signal transferred to chromatographic
software
7
FIGURE 3. Overlays of three separate analyses of the heating
bath silicone oil sample. Only the 50 to 55 minute segment of the
total run (inset) is shown for clarity.
17.4
17.0
pA
15.0
y – Characterization
ermo Scientific™ Dionex™ UltiMate™ 3000
P-3600RS pump, WPS-3000RS autosampler,
TCC-3000RS column oven
ermo Scientific™ Accucore™ 2.6 µm C18,
× 150 mm
°C
hanol
ropanol
mL/min
0 µL
mg/mL silicone oil in chloroform
ona ultra RS
°C
13.0
12.0
11.0
10.0
6.0
5.5
min
49.48
50.00
50.50
80.0
pA
18.0
70.0
100
10
5
0.0
100
10
5
-10.0
15
85
3
100
0
5
100
0
5
reparations - Quantitation
53.00
53.50
54.00
54.50
54.81
pA
12.0
10.0
Curve
5
52.50
14.0
%B
5
52.00
16.0
60.0
%A
100
51.50
FIGURE 4. HPLC chromatogram of a silicone-based topical
product. Product appears to be made of high-molecular weight
polysiloxane (85 minutes) mixed with moderate and lowmolecular weight polysiloxanes. The inset shows the low to
moderate molecular weight regions.
8.0
6.0
4.0
2.0
0.0
min
-2.0
20.0
100
51.00
A silicone-based topical product used for comfort with hearing aids was
characterized using this method, as shown by the chromatogram in
Figure 4. The material appears to contain a moderate amount of
smaller molecular weight polysiloxanes mixed with an amount of higher
molecular weight polysiloxanes that elute at the end of the gradient.
30.0
0
2000
4000
6000
8000
Amount (ng o.c.)
TABLE 1. Response factors of differen
2000 ng o.c. relative to 1000 cP silicone
Amount on
Column (ng)
Sample
Amo
5000
AP200
2000
5000
Heating Bath Oil
2000
FIGURE 6. HPLC chromatogram overla
relief product (blue), dissolved at a con
simethicone in tetrahydrofuran, and 50
oil standard (black)
45.0 pA
40.0
2 - SiliconeOil – 8.06
30.0
8 - Silicone
20.0
5 - 7.954
10.0
0.0
1 - 6.980
2
1
-5.0
6.50
6.80
7.00
7.20
4 - 7.665
- 7.522
2 - 37.452
7.40
7.60
7.80
7 - 8.187
6 - 8.032
9 - 8.4
8.00
8.20
8.40
Sample
Silicone Oil Type
Shampoo
Conditioner
Gas Relief
Product
Dimethicone
Phenyltrimethicone
Simethicone*
Determined
Silicone Oil
(ng o.c.)
3890
2702
4559
*simethicone is a mixture of silica (5.5%) and dimethicone
40.0
0
0
7.0
50.0
Hz
0
cterization:
0
14.0
8.0
were dissolved in chloroform, at a
mately 40 mg/mL.
4
TABLE 2. Quantities of silicone oils fou
16.0
9.0
Characterization
6
Two of the three oils (the two most closely
calibration curve, indicating that calibration
of a similar composition can be used for p
determinations. Differences in chain length
affect retention time. The heating bath oil,
different oil, showed a greater response th
10
1.
2.
3.
4.
5.
6.
7.
8
2
FIGURE 2. Characterization of three different silicone oils, 200 cP
(blue) and 1000 cP (black) viscosities, and a heating bath
silicone oil (pink)
nd Functioning of Charged Aerosol
6
10
Results
e chromatographic methods with the
d aerosol detection provides unique
characterization of a silicone oil sample, as
cone oil-containing samples.
9
12
Peak Area (pA*min)
ector is a sensitive, mass-based detector,
the determination of any nonvolatile analyte
characteristics. As shown in Figure 1, the
n to create aerosol droplets. The mobile
drying tube, leaving analyte particles, which
mixing chamber. The charge is then measured
trometer, providing reproducible, nanogramnology has greater sensitivity and precision
index (RI), is gradient compatible and is
mass spectrometer (MS). Compounds do
romophore (unlike UV detection) or be
0.0
10.0
20.0
30.0
40.0
50.0
60.0
70.0
75.0
10.0
0
5
10
15
20
25
30
35
40
45
50
55
60
65
70
75
80
85
90
min
95
100
The method provides a high-resolution HPLC chromatogram for the
detailed characterization of polysiloxane materials. The use of
the solid core column in this method achieves the high number of
theoretical plates and therefore, the high level of resolution shown in
these figures. The charged aerosol detector provides both sensitive
and consistent response for these analytes.
The near-consistent response of charged aerosol detection for nonAnalysis inof tetrahydrofuran,
Silicone Oils by High
Liquid analytes
Chromatography
Charged
Aerosol
Detection
ne oil were4dissolved
at a Performancevolatile
enablesand
the Corona
quantitation
of total
silicones
in the same
10—20 mg/mL and centrifuged at 10,000 g for
samples used above. The second method, specifically developed for
The measurement of silicone oils in differe
the potential for quantitative determinations
silicone from the sample or having the exa
Samples were dissolved, centrifuged, dilute
analyzed. A gas relieve product chromatog
overlay of 1000 cP silicone oil. The recove
(prepared at 500 µg/mL of simethicone) w
demonstrating the potential for this method
unknown composition in different samples.
Conclusions
Two methods were developed for the char
silicone oils as standards and as part of p
characterization method can readily be mo
of the chromatogram or to fully characteriz
quantification method is sensitive to 100 n
similar oils provide similar response factor
specificity to allow for analysis of different
The use of the solid core C18 column, com
capabilities of the charged aerosol detecto
accurate characterization and quantificatio
containing products.
References
1. DailyMedPlus website
http://www.dailymedplus.com/monograp
4f46-b43c-9ca3d8789740 (last accessed
© 2013 Thermo Fisher Scientific Inc. All rights reserv
Thermo Fisher Scientific Inc. and its subsidiaries. Th
encourage use of these products in any manners tha
Quantitation
o Scientific™ Dionex™ UltiMate™ 3000
400SD pump, WPS-3000RS autosampler,
CC-3000RS column oven
ore 2.6 µm C18, 3.0 × 150 mm
Formic acid/acetonitrile/tetrahydrofuran*
:30), helium sparge
ydrofuran*, helium sparge
0 mL/min
L
a ultra RS
Samples that were tested included a 200 cP silicone oil, the heating bath
oil, and three consumer products, including a shampoo, a hair conditioner,
and a gas relief product containing different forms of silicones. The 200 cP
oil and the heating bath oil were also used to generate single-injection
calibration curves to investigate their response factors, relative to the
1000 cP oil standard. These results are in Table 1.
on:
Time (min)
Flow Rate
(mL/min)
%A
0
4.0
0.6
100
0
0
6.0
0.6
0
100
%B
This quantitative method was evaluated using different silicone oils; using
the 1000 cP silicone oil standards, a calibration curve was generated from
78 to 10,000 ng o.c., as shown in Figure 5. System precision (n=3) was
acceptable, with peak area percent relative standard deviations 0.92
(10,000 ng o.c.) to 7.28 (156 ng o.c.). The quantitation limit is estimated at
approximately 100 ng o.c, based on a signal to noise ratio of 3.0.
%B
0
8.0
0.6
0
100
0
10.0
1.0
0
100
0
12.0
1.0
50
50
14.0
0.6
100
100
The 200 cP oil showed essentially equal response to that of the 1000 cP
oil, but the heating bath oil differed in response at the two amounts used
in this comparison. This may be associated with the differences of the
groups or numbers of associated groups contained on the silicone. Thus,
it is recommended that the silicone oil calibration standard is the same (or
at least similar) to the silicone that is to be quantified. As seen in Figure 2,
there is a clear difference between the 200 and 1000 cP silicones and the
heating bath oil silicone.
FIGURE 5. Silicone oil calibration curves, from 78 to 10,000 ng (1000 cP)
in triplicate, 2000 to 10,000 ng o.c. (200 cP and Heating Bath Oil)
were obtained and compiled using Thermo
meleon™ Chromatography Data Station
10
Peak Area (pA*min)
onses of different oils, three different
haracterized consisting of two similar oils
0 cP and 1000 cP) and a third oil that is
From the overlay of chromatograms shown
sample is comprised of a greater amount of
ysiloxanes (later elution) than the 200 cP oil
y the bulk of peak area at higher retention
s comprised of more isolable polysiloxane
by over 170 different peaks that were at
his oil.
12
AP1000
6
AP200
HeatingOil
4
2
0
0
2000
4000
6000
8000
10000
12000
Amount (ng o.c.)
TABLE 1. Response factors of different polysiloxanes at 5000 and
2000 ng o.c. relative to 1000 cP silicone oil
Sample
on of three different silicone oils, 200 cP
) viscosities, and a heating bath
Amount on
Column (ng)
Amount Found
(ng)
Relative Response
5000
5031
1.006
5000
8681
1.736
AP200
2000
Heating Bath Oil
1994
2000
0.997
4199
2.100
Two of the three oils (the two most closely related) showed a similar
calibration curve, indicating that calibration curves derived from oils
of a similar composition can be used for product concentration
determinations. Differences in chain length and other structures may
affect retention time. The heating bath oil, which characterized as a
different oil, showed a greater response than the viscosity-rated oils.
s demonstrated by repetitive analysis of the
mple (Figure 3). The UltiMate 3000 LC
Chromeleon software, enables sample
d with the pump delivery, allowing for exact
tions for each injection. The percent relative
tion time at 50 minutes was 0.02%.
ee separate analyses of the heating
Only the 50 to 55 minute segment of the
for clarity.
51.50
8
FIGURE 6. HPLC chromatogram overlay of over-the-counter gas
relief product (blue), dissolved at a concentration of 500 µg/mL
simethicone in tetrahydrofuran, and 500 µg/mL of 1000 cP silicone
oil standard (black)
45.0 pA
2 - SiliconeOil – 8.060
40.0
8 - SiliconeOil - 8.295
30.0
20.0
5 - 7.954
10.0
0.0
1 - 6.980
2
1
-5.0
6.50
6.80
7.00
7.20
4 - 7.665
- 7.522
2 - 37.452
7.40
7.60
7.80
7 - 8.187
6 - 8.032
9 - 8.417
8.00
8.20
8.40
8.60
8.80
9.00
9.20
9.40
9.60
9.80
min
10.00
TABLE 2. Quantities of silicone oils found in products.
Sample
Silicone Oil Type
Shampoo
Conditioner
Gas Relief
Product
Dimethicone
Phenyltrimethicone
Simethicone*
Determined
Silicone Oil
(ng o.c.)
3890
2702
4559
Product Silicone
Amount
Recovery
(%)
1.95 w/w-%
2.70 w/w-%
4725 ng o.c.
--96.5
*simethicone is a mixture of silica (5.5%) and dimethicone (94.5%)1
min
52.00
52.50
53.00
53.50
54.00
54.50
54.81
duct used for comfort with hearing aids was
The measurement of silicone oils in different commercial products showed
the potential for quantitative determinations without extraction of the
Thermo Scientific Poster Note • PN70538_e 06/13S 5
silicone from the sample or having the exact silicone oil as a calibrant.
Samples were dissolved, centrifuged, diluted to a targeted amount, and
Shampoo
Conditioner
Gas Relief
Product
3890
2702
4559
1.95 w/w-%
2.70 w/w-%
4725 ng o.c.
--96.5
*simethicone is a mixture of silica (5.5%) and dimethicone (94.5%)1
min
51.50
52.00
52.50
53.00
53.50
54.00
54.50
54.81
oduct used for comfort with hearing aids was
ethod, as shown by the chromatogram in
ears to contain a moderate amount of
polysiloxanes mixed with an amount of higher
anes that elute at the end of the gradient.
atogram of a silicone-based topical
s to be made of high-molecular weight
s) mixed with moderate and lowoxanes. The inset shows the low to
ght regions.
30
Dimethicone
Phenyltrimethicone
Simethicone*
min
20.0
30.0
35
40
40.0
45
50
50.0
55
60
60.0
65
70.0
70
75
75.0
80
85
90
min
95
100
h-resolution HPLC chromatogram for the
f polysiloxane materials. The use of
s method achieves the high number of
efore, the high level of resolution shown in
aerosol detector provides both sensitive
or these analytes.
nse of charged aerosol detection for nonhe quantitation of total silicones in the same
second method, specifically developed for
ous acetonitrile mobile phase with a fast
elute the analyte from the column in a
ear-single peak. Chromatographic baseline
ove baseline deviations that result from the
The measurement of silicone oils in different commercial products showed
the potential for quantitative determinations without extraction of the
silicone from the sample or having the exact silicone oil as a calibrant.
Samples were dissolved, centrifuged, diluted to a targeted amount, and
analyzed. A gas relieve product chromatogram is shown in Figure 6 with an
overlay of 1000 cP silicone oil. The recovery for the gas relief product
(prepared at 500 µg/mL of simethicone) was 96.5%, as shown in Table 2,
demonstrating the potential for this method to measure silicone oils with
unknown composition in different samples.
Conclusions
Two methods were developed for the characterization and quantitation of
silicone oils as standards and as part of products. The long
characterization method can readily be modified to address specific regions
of the chromatogram or to fully characterize a specific oil in less time. The
quantification method is sensitive to 100 ng o.c. and it was shown that
similar oils provide similar response factors. The method also had sufficient
specificity to allow for analysis of different products and silicone oils.
The use of the solid core C18 column, combined with the detection
capabilities of the charged aerosol detector, enables convenient and
accurate characterization and quantification of silicone oils and silicone oilcontaining products.
References
1. DailyMedPlus website
http://www.dailymedplus.com/monograph/view/setid/da8eba22-33e14f46-b43c-9ca3d8789740 (last accessed 30 Jan 13).
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PO738_E 03/13S
6 Analysis of Silicone Oils by High Performance Liquid Chromatography and Corona Charged Aerosol Detection
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