Download Industrial Applications with a New Polyethylene Glycol

Industrial Applications with a New
Polyethylene Glycol-Based GC
Column
Application Note
Authors
Abstract
Taylor Hayward1, Yujuan Hua1,
The increasing need for sensitive, reproducible, and reliable analysis of active
Ronda Gras1,2 , and Jim Luong1,2
analytes is placing demands on GC column technology. These analyses are
Dow Chemical Canada ULC
1
PO BAG 16, Highway 15,
Fort Saskatchewan,
Alberta, T8L 2P4
Australian Centre for Research
2
on Separation Science (ACROSS)
University of Tasmania,
Private Bag 75, Hobart,
Tasmania 7001, Australia
Gary Lee, Allen Vickers, and
Ngoc A Dang
Agilent Technologies, Inc.
challenging due to potential adsorption of analytes to the active sites in the GC
flowpath. Agilent Technologies has recently produced an Agilent J&W DB-WAX
Ultra Inert GC column. This highly inert capillary column is coated with an
innovative new polyethylene glycol (PEG) stationary phase. This application note
demonstrates the excellent inertness performance of this stationary phase in the
analysis of compounds with polar functional groups. The column was found to be
suitable for many challenging industrial applications.
Introduction
In gas chromatography, the column is the heart of the system where separation
of sample components takes place through interactions between analytes and the
stationary phase. GC columns with polyethylene glycol (PEG) stationary phase are
widely used for analyzing compounds with polar functional groups. PEG phase
demonstrates a unique separation mechanism based on hydrogen bonding, and
acid-base interaction, making it suitable for many industrial applications. It is
also a good option for offering phase orthogonality in techniques such as GC-GC
or GC×GC. However, PEG-based columns are less stable, less robust, and have a
lower maximum operating temperature when compared to most polysiloxane-based
columns. They exhibit shorter lifetimes, and are more susceptible to damage upon
overheating or exposure to oxygen.
Samples, chemicals, and reagents
Traditional PEG columns have constraints particularly with
active polar compounds such as alcohols, aldehydes, and
organic acids due to a lack of overall stationary phase
inertness [1]. These molecules can either adsorb or absorb
onto active sites in the stationary phase, resulting in lower
responses and tailing peaks, which can compromise system
reliability and performance.
Three test mixes: a DRO/ORO range calibration standard,
a polar ISO test mix, and a Grob test mix were obtained
from Restek Corporation (Bellefonte, Pennsylvania). An
eight-component phenol mix was prepared in cyclohexane.
Chlorinated hydrocarbons in process water were extracted 1:1
with cyclohexane using a piston-extraction device [5]. Butyl
phenyl ether, dimethoxybenzene, and trimethoxybenzene
were prepared at a concentration of 100 μg/mL in hexane.
Chemicals and solvents used for standard and sample
preparation were obtained from Sigma-Aldrich.
Recent advances in surface deactivation techniques and high
efficiency static coating technologies led to the development,
commercialization, and implementation of an improved
generation of PEG columns. These columns include the
Agilent J&W DB-WAX Ultra Inert GC column, which has a
high degree of inertness [1-4].
Results and Discussion
This application note evaluates the Agilent DB-WAX Ultra
Inert column in terms of efficiency, reactivity, and overall
inertness against various, challenging industrial applications.
Testing the columns using demanding test probes containing
problematic compounds including alcohols, aldehydes, and
organic acids, proved the high inertness performance of the
column.
Test methods and standards
To evaluate the overall performance of the new stationary
phase, three test mixes were analyzed.
• A 12 component DRO/ORO range calibration standard:
A 12 component DRO/ORO range calibration standard,
with carbon numbers from C10 to C32, was analyzed on
a DB‑WAX Ultra Inert column to assess the hydrocarbon
range. The chromatogram in Figure 1 shows that all
hydrocarbon compounds eluted with sharp symmetrical
peaks.
Experimental
Instrumentation
An Agilent 7890A+ network GC, equipped with an
Agilent 7693 autosampler, two split/splitless inlets, and a
flame ionization detector was used in this study. Table 1
summarizes the instruments and conditions. Chromatographic
data were obtained with Agilent ChemStation software
version B.04.03.SP.
1
175
Table 1. GC conditions.
Value
GC System:
Agilent 7890A+/FID
Column:
Agilent J&W DB-WAX Ultra Inert, 20 m × 0.18 mm, 0.3 µm
(p/n 121-7023UI)
Autosampler:
Agilent 7693, 1.0 µL injection volume
Carrier gas:
Hydrogen, constant flow mode, 28 cm/sec
Inlet:
Split/splitless, 250 °C, split ratio 25:1, equipped with an
Agilent Ultra Inert inlet liner (p/n 5190–2294)
Oven:
40 °C (1 minute) to 250 °C at 20 °C/min
FID
250 °C, H2 30 mL/min, air 350 mL/min, N2 30 mL/min
(constant column + make up flow)
3
150
125
4
5
6
7 8
7. (C22) n-Docosane
8. (C24) n-Tetracosane
9. (C26) n-Hexacosane
10. (C28) n-Octacosane
11. (C30) n-Triacontane
12. (C32) n-Dotriacontane
9
10
Norm
Parameter
2
Peak ID
1. (C10) n-Decane
2. (C12) n-Dodecane
3. (C14) n-Tetradecane
4. (C16) n-Hexadecane
5. (C18) n-Octadecane
6. (C20) n-Eicosane
100
11
75
12
50
25
0
0
5
10
15
20
25
Acquisition time (min)
30
35
Figure 1. Analysis of a hydrocarbon mix, with carbon numbers
from C10 to C32, separated using an Agilent J&W DB-WAX
Ultra Inert GC column.
2
• A polar ISO column test mix: A polar ISO column test
mix was used for detection of column activity. This mix
contained representative compounds with different
polar functional groups including aniline, chlorophenol,
alcohol, ester, and ketone with long hydrocarbon chains.
Figure 2 shows the symmetrical peak shapes for all the
active components, including the basic compound aniline
(Peak 3), indicating the high level of inertness of the
DB‑WAX Ultra Inert column.
• A Grob test mix (12 components): In addition to the
polar ISO column test mix, a more demanding test mix,
a Grob mix, was analyzed for extra assessment of the
inertness performance of the DB-WAX Ultra Inert column.
This mix contained more challenging test probes such as
2,3-butanediol, dicyclohexylamine, and 2-ethylhexanoic
acid. The new column showed excellent separation
capabilities and peak efficiencies, as illustrated in Figure 3.
Compounds such as dicyclohexylamine, 2,3-butanediol,
and 2-ethylhexanoic acid can have less than ideal
chromatographic performance, as reported in the
literature. Figure 3 shows that these active components
exhibited excellent peak symmetry with the DB-WAX Ultra
Inert column.
Peak ID
1. (C17) n-Heptadecane
2. (C19) n-Nonadecane
3. Aniline
4. 2-Chlorophenol
5. 2-Dodecanol
6. Methyl dodecanoate
7. 2-Nonanone
8. 1-Octanol
200
3
150
Norm
1
5
2
100
4
6 8
7
1
50
2
4
6
8
10
12
Acquisition time (min)
14
16
2
18
4
Norm
0
Peak ID
1. Decane
2. Undecane
3. Nonanal
4. 2,3-Butanediol
5. 1-Octanol
6. 2,3-Butanediol (isomer)
7. Methyl decanoate
9
6
3
5
Figure 2. Analysis of a polar ISO test mix separated using an
Agilent J&W DB-WAX Ultra Inert GC column.
5.0
7.5
8. Dicyclohexylamine
9. Methyl undecanoate
10. Methyl dodecanoate
11. 2,6-Dimethylaniline
12. 2,6-Dimethylphenol
13. 2-Ethylhexanoic acid
10
11 12
13
8
10.0
12.5
Acquisition time (min)
15.0
17.5
Figure 3. GC/FID chromatogram of a Grob test mix separated
using an Agilent J&W DB-WAX Ultra Inert GC column.
3
Hydrolysis and swelling studies
Applications
Some traditional PEG stationary phases can become unstable
with aqueous injection, leading to column degradation,
reduced lifetime, and poor reproducibility. To evaluate the
performance of the DB-WAX Ultra Inert column for aqueous
injection, the polar ISO test mix was analyzed repeatedly with
30 water injections (1 µL) between sample injections. The
results showed no retention time stability drift resulting from
repeated injections of water. Separation and peak shape were
also maintained over the course of 150 injections of water
(Figure 4). The DB-WAX Ultra Inert column demonstrated
excellent inertness and phase stability for aqueous injections.
The high tolerance towards water allows the direct injection
of aqueous samples, which offers the benefit of rapid analysis
without the need of tedious sample pretreatment procedures.
Chlorinated hydrocarbons in process water
Chlorinated hydrocarbons have many industrial applications,
including the manufacture of industrial solvents and
pesticides. Improper disposal practices or accidental spills of
these compounds may pose a threat to environmental health.
Thus, effective monitoring and control of these contaminants
are essential. Figure 5 shows the analysis of chlorinated
hydrocarbons in process water. Five chlorinated hydrocarbon
compounds were detected, and all eluted with sharp and
symmetrical peaks.
35
30
120
Norm
100
3
5
pA
20
1
2
15
10
5
80
5
60
10
15
Acquisition time (min)
20
25
Figure 5. Separation of chlorinated hydrocarbon compounds in
process water using an Agilent J&W DB-WAX Ultra Inert GC
column.
40
20
0
4
25
0 Water injections
30 Water injections
60 Water injections
90 Water injections
120 Water injections
150 Water injections
140
Peak ID
1. Tetrachloroethane
2. Hexachlorobutadiene
3. Hexachloroethane
4. Pentachlorobenzene
5. Hexachlorobenzene
10
11
12
13
14
Acquisition time (min)
15
16
Figure 4. Repeated analysis of the Polar ISO mix on an
Agilent J&W DB-WAX Ultra Inert GC column with 30 water
injections (1 µL) between sample injections.
4
Analysis of phenols in fuels and lubricants
Nonradioactive bulk transfer compounds
A wide range of phenolic compounds including phenol and
tert-butyl phenol have been found in the antioxidants package
in fuels and lubricants. Figure 6 shows an overlay of three
chromatograms of the separation of a phenol standard mix
containing eight popular phenolic compounds in cyclohexane
(100 ppm w/w each). Respectable separation and peak
asymmetry were obtained for these compounds. The overlaid
chromatograms from three replicate injections show excellent
retention time repeatability for all components. These
phenolic compounds are also commonly encountered in
various industrial processes such as pulp and paper, dyes,
and textiles.
Nonradioactive bulk transfer compounds can be added to
products as unique product markers against counterfeiting
and for product authentication. These compounds can
be added into complex matrices, and are used for the
assessment of sample integrity and source identification.
Often, these compounds are functionalized, making the
analysis challenging due to interactions between analytes
and flowpath surfaces. Figure 7 shows the separation of butyl
phenyl ether, dimethoxybenzene, and trimethoxybenzene.
These are commonly used as marker compounds for
petroleum hydrocarbons as well as for other fuels and oils.
The DB‑WAX Ultra Inert GC column delivered sharp and
symmetrical peak shape for all three compounds. Retention
times and peak shapes were consistent for three triplicate
injections, as illustrated in the inset for butyl phenyl ether,
indicating the stability and inertness of the DB-WAX Ultra
Inert column.
35
30
pA
25
20
15
10
Peak ID
1. 2,6-Di-tert-butyl phenol
2. 2,6-Di-tert-butyl-1,4-methyl phenol
3. o-Cresol
4. Phenol
5. 2,5-Dimethylphenol
6,7. p-Ethylphenol and 3,5-Dimethylphenol
8. 2,3,5-Trimethylphenol
3
1
2
4
6,7
8
5
1
40
35
2
30
16
17
18
Acquisition time (min)
19
Norm.
5
20
25
Peak ID
1. Butylphenyl ether
2. Dimethoxybenzene
3. Trimethoxybenzene
3
20
15
Figure 6. Analysis of phenols in fuels and lubricants using an
Agilent J&W DB-WAX Ultra Inert GC column.
10
5
5
10
15
Acquisition time (min)
20
Figure 7. Analysis of fuel marker compounds using an
Agilent J&W DB-WAX Ultra Inert GC column.
5
Select volatile organic compounds
Constrains – highly basic compounds
Light hydrocarbons of industrial importance can be active
and adsorptive, making the analysis of these molecules
problematic, with tailing peaks and loss of response.
Therefore, an inert column is critical for accurate
quantification, especially for components at trace levels.
Figure 8 demonstrates that the new stationary phase showed
a high degree of inertness for volatile compounds, even with
highly active compounds such as acetaldehyde (Peak 6). This
inert column provides excellent peak shapes, even at low
concentrations (0.5–1 ppm, blue trace), allowing for easier
integration and more reliable quantification at low levels.
The analysis of highly basic compounds, such as amines,
is a challenging chromatographic application due to their
reactivity and adsorption to active surfaces. As demonstrated
in Figure 9, mono-ethanolamine (MEA) and methyl
diethanolamine (MDEA) exhibited severe peak tailing due to
interaction between analytes and the stationary phase.
45
1
40
Peak ID
1. Methanol
2. MEA
3. LFGA
4. MDEA
3
35
6
pA
5
4
3
Peak ID
1. Acetylene – 5.1 ppm
2. Ethylene – 5.4 ppm
3. Cyclopropane – 10.4 ppm
4. Methyl chloride – 10.3 ppm
5. Vinyl chloride – 10.3 ppm
6. Acetaldehyde – 10.5 ppm
Carbon dioxide – 10.3 ppm
(not observed)
pA
30
3
20
15
1
2
2
10
5
12
4
3
4
Acquisition time (min)
4
5
5
6
5
10
15
Acquisition time (min)
20
Figure 9. Analysis of highly basic compounds using an
Agilent J&W DB-WAX Ultra Inert GC column. LFGA: low
freezing grade amine, MEA: mono-ethanolamine,
MDEA: methyl diethanolamine.
2
1
25
6
Figure 8. Analysis of volatile organic compounds using an
Agilent J&W DB-WAX Ultra Inert GC column. Concentrations
are for the red trace chromatogram. The blue trace is a 1 to
10 dilution of the gas standard (0.5–1 ppm range).
6
Conclusions
Acknowledgements
The Agilent DB-WAX Ultra Inert column delivers improved
performance over classical PEG stationary phases, giving
better peak shapes and improved sensitivity for active
compounds. The improvement in inertness contributes to
the overall total inert flowpath. Assessment of hydrolysis
and swelling of the stationary phase in aqueous injections
demonstrated no loss in inertness, allowing for direct
aqueous sample analysis. The DB-WAX Ultra Inert column
was found suitable for use in various industrially significant
applications for analysis of polar compounds due to its
high degree of inertness. These applications included the
determination of phenol and alkylated phenols used as
antioxidants in fuels and lubricants, nonradioactive bulk
transfer compounds such as fuel marker compounds, and
volatile organic compounds. The column phase can also
be used for both multidimensional and comprehensive gas
chromatography to enhance selectivity and chromatographic
system peak capacity per unit time.
Dr. Janice Perez, Agilent Technologies, Middelburg, the
Netherlands, and Dr. Tonya Stockman are acknowledged for
their support and encouragement. This project is partially
funded by the 2016 Analytical Technology Center’s Technology
Renewal and Development Funds.
References
1. Dang, N.; Vickers, A. K. A New PEG GC Column with
Improved Inertness Reliability and Column Lifetime;
Competitive Comparison, Agilent Technologies, Inc.
Publication number 5991-6683EN, 2016.
2. Zou, Y. Lavender Oil analysis using Agilent J&W
DB‑WAX Ultra Inert Capillary GC Columns; Application
note, Agilent Technologies, Inc. Publication number
5991‑6635EN, 2016.
3. Zou, Y. GC Analysis of Glycols in Toothpaste;
Agilent Technologies, application note. Publication number
5991-6637EN, 2016.
4. Lynam, K.; Zou, Y. Analysis of Distilled Spirits using
Agilent J&W DB-WAX Ultra Inert Capillary GC
Column; Application note, Agilent Technologies, Inc.
Publication number 5991-6638EN, 2016.
5. J. Luong, R. Gras, K. Gras, R. A. Shellie. Piston-cylinderbased micro liquid-liquid extraction with GC-qMS for trace
analysis of targeted chlorinated compounds in water.
Canadian Journal of Chemistry 2015, 93(11), 1283-1289.
7
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© Agilent Technologies, Inc., 2017
Printed in the USA
March 23, 2017
5991-7961EN