introduction,instrumentation,characterization of a water stationary phasein cgas chromatography

1. INSTRUMENTATION AND CHARACTERIZATION OF A WATER
STATIONARY PHASE IN cGAS CHROMATOGRAPHY
PRESENTED BY
P.ANURADHA
614275804016
Shri Vishnu College of Pharmacy
(M.PHARMACY)
Pharmaceutical Analysis&Quality Assurance

2. INTRODUCTION
Gas chromatography (GC) is a widely used separation technique in analytical
chemistry. The purpose of GC is the separation of different chemical species in a
sample based on their interaction with a stationary phase fabricated from a non-
volatile liquid or solid. The sample is transported over the stationary phase by an inert
carrier gas. The weakly interactive compounds will move over the stationary phase
quicker than the strongly interactive compounds.
GAS CHROMATOGRAPHY OVERVIEW

3. Carrier Gas
Flow Control Injector
Column
Oven
Detector
Analyte peaks
Recorder
THE MODERN GC INSTRUMENT

4. GC COLUMNS
• In the early years of GC, the majority of work was performed on columns that were
a few meters long, had a diameter of a few millimeters, and were packed with
particles with a non-volatile liquid coating . This mode of separation was termed
packed GC (pGC) due to the column containing a packed stationary phase.
• In 1957, Martin suggested using an open tubular design for a GC column in which a
stationary phase could be coated on the inside walls of the column .
• This concept was also independently realized by Golay in 1958. Their combined
efforts began the field of what is now known as capillary gas chromatography
(cGC).

5. • The columns used in cGC can typically separate closely eluting compounds from a
sample more clearly than columns used in pGC and can allow for a lower amount
of analyte to be detected in a sample.
• This is mainly due to lower flow rates in cGC resulting in lower detector noise and
better signal to noise ratios.
• Some of these differences include the fact that cGC columns are typically much
longer (15 - 100 m) than pGC (1 - 5 m),cGC columns also possess a smaller I.D.
(typically 240 - 530 µm) than pGC columns (3 - 6 mm) .

6. • The stationary phase is the primary component in GC that causes analytes to
separate.
• A variety of stationary phases have been applied to a fused silica capillary
substrate in cGC, including methyl polysiloxanes, phenyl polysiloxanes, cyano-
propyl polysiloxanes and polyethylene glycol (PEG).
One compound that may provide a highly polar stationary phase with interesting
selectivity is water. Water is a very polar compound which has several advantages in a
laboratory setting such as low economic cost,low ernvironmental impact and the ease
andf safety of use.
DIFFERENT STATIONARY PHASES IN MODERN cGC
CURRENT cGC STATIONARY PHASE RESEARCH
PROPERTIES OF WATER AS A STATIONARY PHASE

7. • A water stationary phase can offer a very high polarity stationary phase at little cost
to create and use. This also does not involve any harmful chemicals.
• Here we are disscussing on the formation, maintenance, characterization and
utilization of a water stationary phase in cGC.
 The first part of the study will investigate the formation and maintenance of a water
phase in cGC.
 The second part of this study will focus on the characterization of this stationary
phase in cGC.
STATEMENT OF PURPOSE

8. General Instrumentation
He
Tank Transfer Line
Humidifier
Pre-Heating Coi
Inj.
SS Column
Restrictor
FID
ZDV
Union
Schematic diagram of the water stationary phase instrument.

9. Humidifier and Pre-Heating Coil
• To properly humidify the carrier gas , a custom humidifer was developed for this
novel stationary phase and its schematic is represented by
He Flow Inlet
Swagelok Cross Union
Pre-Heating Coil
Humidified He
Flow Outlet
Humidified He
Water
in the
SS
tubing

10. Injector
SS Column
SS Tee union
Sample
injection needle
Septum
SS Pre-heating
coil
Carrier gas
flow
SS Tee union modified injector.

11. Post –Column Restrictor
• Once the analytes eluted from the column, they entered the restrictor.
• Several advantages in the system such as: further determent of the depletion of the
water stationary phase on the column, increased oven temperatures that could be
used with the water stationary phase and direct column effluent deposition at the
base of the FID flame.
• The dimensions of the fused silica capillary tubing for this restrictor was optimized
at 350 µm O.D. × 50 µm I.D. × 11 cm length and this fused silica was replaced
every 5-6 trials. The end of the restrictor was placed at the base of the flame in the
FID to guide the effluent into the FID flame directly.

12. Flow pathway
SS column
SS Zero Dead Volume
union
PEEK Tubing
Sleeve
Fused Silica Capillary Restrictor
Diagram of the column and restrictor connection.

13. Water stationary phase deposition
• To deposit this water stationary phase on the SS column, a unique method and
apparatus was employed
• This method and apparatus is similar to the standard dynamic coating of a
stationary phase.
N2
N2 Transfer line
Reservoir
SS Column
ZDV union
Water

14. CHARACTERIZATION OF THE WATER STATIONARY PHASE
THE CARRIER GAS HUMIDIFER
• Taking this into account, the carrier gas was humidified and its effect on the
stability of the cGC water stationary phase was studied by comparing the loss in
the retention time of a consecutive series of acetone injections.
• This was done with identical stationary phase formation and operating
conditions, except for the presence or the absence of the humidifier.

15. As is shown, the % loss with the humidifier is significantly lower than without the
humidifier. Therefore, the humidifier significantly stabilized the stationary phase at a
large range of temperature.
Figure:Retention time of acetone over time showing the increase in
stationary phase stability provided by the humidifier. The oven was
set to 70 şC.

16. POST COLUMN RESTRICTION
• Even with the increased stability which was provided by the water
humidifier, at temperatures at or above 100 C, the water stationary phase
experienced rapid depletion.
• To aid in its stability at these higher oven temperatures, a post-column restrictor
was employed that introduced backpressure on the column and the stationary
phase.

17. This figure demonstrates that the restrictor does improve the stability of the stationary
phase even at low oven temperatures
Figure:Retention time of acetone over time showing the effect of the
post-column restrictor on water stationary phase stability. The oven was
kept at 70 şC and the restrictor dimensions were 323 µm O.D. × 50 µm
I.D. × 11 cm length, requiring 90 psi of column head pressure.

18. Optimizing of Post Column Restrictor
Peak shapes for acetone injections showing the optimization of the post-column
restrictor. The column head pressures and dimensions used were A) 90 psi with 50 µm
I.D. × 11 cm length, B) 50 psi with 100 µm I.D. × 1 m length and C) 30 psi with 250
µm I.D. x 14 cm length. The carrier gas linear velocity was 26 cm/s for all profiles.
The temperatures indicated are the oven temperature for the elution below them.

19. CUSTOM INJECTOR
Chromatogram demonstrating the peak shape provided by the modified
injector. The conditions for this injection were as follows: 5 µg of acetone
in CS2, 220 şC injector, 60 şC oven and a carrier gas linear velocity of 26
cm/s.

20. MAXIMUM OVEN TEMPERATURE
As seen, properly shaped peaks were obtained up to a maximum operating
temperature of 140 şC. However, higher temperatures began to onset peak asymmetry
and complete disruption of the separation system. Going forward then, 140 şC was
determined to be the maximum that could be used for this current water stationary phase
setup.

21. APPLICATIONS
1. For determination of straight chain alkanes
The chromatogram for a series of straight chain alkane (C6-C20) injections on the water
stationary phase at 140 şC.
2. For BTEX analysis which are collectively knowm as benzene,toulene,ethyl benzene,m-
xylene,o-xylene which are significally in air pollution and soil contanimation investigation.

22. 3.For determination of oxygenates,sulfur compounds in gasoline matrix
4.For investigation of 3 different aqueous products tequila,vanilla,window cleaner
examined for alcohol content.

23. REFERENCES
• Gallant, Jonathan A., and Kevin B. Thurbide. "Properties of water as a novel
stationary phase in capillary gas chromatography." Journal of Chromatography A
1359 (2014): 247-254.
• Murakami, Jillian N., and Kevin B. Thurbide. "Coating properties of a novel water
stationary phase in capillary supercritical fluid chromatography." Journal of
separation science 38.9 (2015): 1618-1624.

24. THANK YOU