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EXPERIMENT REPORT
GAS CHROMATOGRAPHY
By :
Ulifatul Laili 103194035
Meyta Rosemala Dewi 103194057
Rizki Putri Wardani 103194080
INTERNATIONAL CHEMISTRY EDUCATION 2010
SURABAYA STATE UNIVERSITY
MATHEMATICS AND SCIENCES FACULTY
CHEMISTRY DEPARTMENT
2012
Experiment Result GAS CHROMATOGRAPHY
A. Title : Gas Chromatography (GC)
B. Purpose :
- To understand preparation of Gas
Chromatography (GC) instrument
- To solve condensation problem in Gas
Chromatography (GC) instrument
C. Date of Experiment : December 12th , 2012
D. Basic theory :
Gas chromatography, the components of a Vaeporized sample are separated as a
consequence of being partitioned between a mobi gaseous phase and a liquid or a solid
stationary phase held in a column. In performing a gas chromatpgraphic separation, the
sample is vaporized and;injected onto the head of a chromatographic column is brought
about by the flow of an inert gaseous mobile phase. Tn contrast to most other type of
chromatography, the mobile phase does not (interact with molecules of the analyte; its only
function is to transport the analyte through the column.
There are two types of gas chromatography: gas-liquid chromatography (GLC) and
gas-solid chromatugraphv (GSC). OLC finds widespread use in all fields of science; its
name is usually shortened to gas chromatography (GC).'In GLC the analyte is partitioned
between a gaseous mobile phase and a liquid phase immobilized on the surface of an inert
solid packing or on the walls of a capillary tubing. The concept of OLC was first suggested
in 1941 by Martin and Synge, who were also responsible for the development of liquid-
liquid partitiun chromatography. More than a decade was to ellapse, however, before the
value of GLC was demonstrated experimentally' and this technique began to be used as a
routine laboratory tool. In 1955 the first commercial apparatus for GLC appeared on the
market. Since that time, the growth in applications of this technique has been phenomenal.
Currently, nearly a million gas chromatographs are in use throughout the world In the
procedural GC instrument, there are 3 tubes in the instrumkent laboratory, oxygen, nitrogen
and hydrogen.
Experiment Result GAS CHROMATOGRAPHY
Instrument of GC
The mobile-phase gas in GC is called the carrier gas and must be chemically inert.
Helium is the most common mobile-phase gas used, although argon, nitrogen, and hydrogen
are also used. These gases are available in pressurized tanks. Pressure regulators, gauges, and
flow meters are required to control the flow rate of the gas. In addition, the carrier gas system
often contains a molecular sieve to remove impurities and water. Flow rates are normally
controlled by a two-stage pressure regulator at the gas cylinder and some sort of pressure
regulator or flow regulator mounted in the chromatograph. Inlet pressures usually range from
10 to 50 psi (Ib fin. ') above room pressure, which lead to flow rates of 25 to 150 mL/min with
packed columns and 1 to 25 mL/min for open tubular capillary columns. Generally, it is
assumed that flow rates will be constant if the inlet pressure remains constant. Flow rates can
be established by a rotometer at the column head.
Gas chromatography - specifically gas-liquid chromatography - involves a sample
being vapourised and injected onto the head of the chromatographic column. The sample is
transported through the column by the flow of inert, gaseous mobile phase. The column itself
contains a liquid stationary phase which is adsorbed onto the surface of an inert solid. Have a
look at this schematic diagram of a gas chromatograph:
Experiment Result GAS CHROMATOGRAPHY
Instrumental components
Carrier gas
The carrier gas must be chemically inert. Commonly used gases include nitrogen,
helium, argon, and carbon dioxide. The choice of carrier gas is often dependent upon the type
of detector which is used. The carrier gas system also contains a molecular sieve to remove
water and other impurities.
Sample injection port
For optimum column efficiency, the sample should not be too large, and should be
introduced onto the column as a "plug" of vapor - slow injection of large samples causes band
broadening and loss of resolution. The most common injection method is where a micro
syringe is used to inject sample through a rubber septum into a flash vaporizer port at the head
of the column. The temperature of the sample port is usually about 50°C higher than the
boiling point of the least volatile component of the sample. For packed columns, sample size
ranges from tenths of a micro liter up to 20 micro liters. Capillary columns, on the other hand,
need much less sample, typically around 10-3 mL. For capillary GC, split/split less injection is
used.
Experiment Result GAS CHROMATOGRAPHY
Have a look at this diagram of a split/split less injector :
The injector can be used in one of two modes; split or splitless. The injector contains
a heated chamber containing a glass liner into which the sample is injected through the
septum. The carrier gas enters the chamber and can leave by three routes (when the injector is
in split mode). The sample vapourises to form a mixture of carrier gas, vapourised solvent and
vapourised solutes. A proportion of this mixture passes onto the column, but most exits
through the split outlet. The septum purge outlet prevents septum bleed components from
entering the column.
Columns
There are two general types of column, packed and capillary (also known as open
tubular). Packed columns contain a finely divided, inert, solid support material (commonly
based on diatomaceous earth) coated with liquid stationary phase. Most packed columns are
1.5 - 10m in length and have an internal diameter of 2 - 4mm.
Capillary columns have an internal diameter of a few tenths of a millimeter. They
can be one of two types; wall-coated open tubular (WCOT) or support-coated open tubular
(SCOT). Wall-coated columns consist of a capillary tube whose walls are coated with liquid
stationary phase. In support-coated columns, the inner wall of the capillary is lined with a thin
layer of support material such as diatomaceous earth, onto which the stationary phase has
Experiment Result GAS CHROMATOGRAPHY
been adsorbed. SCOT columns are generally less efficient than WCOT columns. Both types
of capillary column are more efficient than packed columns.
In 1979, a new type of WCOT column was devised - the Fused Silica Open Tubular
(FSOT) column :
These have much thinner walls than the glass capillary columns, and are given
strength by the polyimide coating. These columns are flexible and can be wound into coils.
They have the advantages of physical strength, flexibility and low reactivity.
Column temperature
For precise work, column temperature must be controlled to within tenths of a
degree. The optimum column temperature is dependant upon the boiling point of the sample.
As a rule of thumb, a temperature slightly above the average boiling point of the sample
results in an elution time of 2 - 30 minutes. Minimal temperatures give good resolution, but
increase elution times. If a sample has a wide boiling range, then temperature programming
can be useful. The column temperature is increased (either continuously or in steps) as
separation proceeds.
Detectors
There are many detectors which can be used in gas chromatography. Different
detectors will give different types of selectivity. A non-selective detector responds to all
compounds except the carrier gas, a selective detector responds to a range of compounds with
a common physical or chemical property and a specific detector responds to a single chemical
compound. Detectors can also be grouped into concentration dependant detectors and mass
flow dependant detectors. The signal from a concentration dependant detector is related to the
Experiment Result GAS CHROMATOGRAPHY
concentration of solute in the detector, and does not usually destroy the sample Dilution of
with make-up gas will lower the detectors response. Mass flow dependant detectors usually
destroy the sample, and the signal is related to the rate at which solute molecules enter the
detector. The response of a mass flow dependant detector is unaffected by make-up gas. Have
a look at this tabular summary of common GC detectors:
Detector TypeSupport
gasesSelectivity Detectability
Dynamic range
Flame ionization (FID)
Mass flowHydrogen and air
Most organic cpds. 100 pg 107
Thermal conductivity (TCD)
Concentration Reference Universal 1 ng 107
Electron capture (ECD)
Concentration Make-upHalides, nitrates, nitriles, peroxides, anhydrides, organometallics
50 fg 105
Nitrogen-phosphorus
Mass flowHydrogen and air
Nitrogen, phosphorus 10 pg 106
Flame photometric (FPD)
Mass flow
Hydrogen and air possibly oxygen
Sulphur, phosphorus, tin, boron, arsenic, germanium, selenium, chromium
100 pg 103
Photo-ionization (PID)
Concentration Make-up
Aliphatics, aromatics, ketones, esters, aldehydes, amines, heterocyclics, organosulphurs, some organometallics
2 pg 107
Hall electrolytic conductivity
Mass flowHydrogen, oxygen
Halide, nitrogen, nitrosamine, sulphur
The effluent from the column is mixed with hydrogen and air, and ignited. Organic
compounds burning in the flame produce ions and electrons which can conduct electricity
through the flame. A large electrical potential is applied at the burner tip, and a collector
electrode is located above the flame. The current resulting from the pyrolysis of any organic
compounds is measured. FIDs are mass sensitive rather than concentration sensitive; this
gives the advantage that changes in mobile phase flow rate do not affect the detector's
response. The FID is a useful general detector for the analysis of organic compounds; it has
Experiment Result GAS CHROMATOGRAPHY
high sensitivity, a large linear response range, and low noise. It is also robust and easy to use,
but unfortunately, it destroys the sample.
E.Tool and Materials :
Tools
Gas chromatography instrument is completed with N2 gas (Ultra High
Pressure), O2 gas as compress air (High Pressure), H2 gas (Ultra High
Pressure)
ADC as connector between GC and computer
Computer
Experiment Result GAS CHROMATOGRAPHY
N2 gasO2 gas
H2 gas
Pressure of each gas in psi or bar
is opened directlyis opened by using spanner
is opened by using spanner
GC, ADC, and computer
GC, ADC, and computer is ready
is turned on
PREPARATION AND
CONDITIONING
INSTRUMENT
F.Procedure :
- Preparation of Gas chromatography instrument
This observation only doing in preparation.
G. Data of experiment :
Pressure of gases in Gas chromatography
Gas Pressure
(bar)
Pressure
(psi)
Properties
N2 100 1500 Ultra High Pressure
(UHP)
O2 as 120 1700 High Pressure (HP)
Experiment Result GAS CHROMATOGRAPHY
compress air
H2 110 1550 Ultra High Pressure
(UHP)
H. Analysis :
This experiment has objective to understand preparation of Gas
Chromatography (GC) only. In Firstly, we have to open gases that used for
gas chromatography, there are N2 gas, O2 gas as compress air and H2 gas,
all of the gas must be openned begin. N2 and H2 has UHP (Ultra High
Pressure). For open that gases, we need different way for each gases. For
N2 gas, we can open it directly. But for O2 gas and H2 gas we have to use
spinner, spinner number 6 for O2 gas and number 8 for H2 gas. After we
open the gases, we also record the gases pressure, it can be in psi or in
bar unit. It’s for knowing flowing of the gases. The steps are start from
open gas N2 ,O2 and the last is H2. O2 should be opened before H2 gas to
prevent flame exploded in GC instrument. After gas opened we should turn
on instrument GC, ADC as a connector because we use instrument GC that
old type and the computer as output data .
After all of tools is turned on, we have to do conditioning to GC
instrument before we can use it. Conditioning need a time around 1 hour.
When conditioning, gas N2 should not turned off because it can broke GC
column. There are occur several mistake when prepare GC instrument, this
instrument is occur condensation. In this condition, instrument will be
moist. The other indication shows that the instrument contain noise is too
high in detector temperature. Normal temperature detector is 200° C. in
this observation the tempeture is more than 200° C. Beside that, output of
computer can also shows that our GC instrument is in unwell condition.
The spectrum that in computer shown there are many pick that cery
crowded, it means that the detector contain noise.
So, it is positive if GC instrument is condensed and the detector in
bad condition. To solve this problem, we make temperature of detector
Experiment Result GAS CHROMATOGRAPHY
higher, it is about 250°C to remove the noise. But it is doesn’t work. So,
we have to do destruction for the detector. Before we do destruction for
the detector. We have to turn off all of the instrument first. Before to do it,
it must be attention to switch off the instrument the N2 gas must be still, it
for to protect the GC instrument not broken. Temperature of detector,
injector and the oven must be down before, minimum 100°C as a safety
temperature when switch off instrument. After to do it, we can switch off
the instrument.
Then we can do destruction. The destruction is done by upper part
of GC instrument. Next is releasing the detector in this instrument, rinse
with methabol and drying with dry and celan fabric. Before releasing the
detector, must be attetntion that the detector must be cold, because in
this part there is fire and the process of combustion.
To minimalize this problem, we can do destruction from the
beginning. So before swith on the instrument, we can take the detector
and rinse with methanol then dry and clean with fabric. So we can make
sure that the detector is clean and not wet. And we must do conditioning
of instrument, so we can do efficient of time with well.
I. Conclusion :
- Condensation problem in Gas Chromatography (GC) instrument can
be solved by elevating the temperature of detector until reach
250°C, and next do destruction of detector.
Experiment Result GAS CHROMATOGRAPHY
The part that must be release
J. Reference :
Anonynomous. (online). http:// en.wikipedia.org/ Gas_chromatography . Access on
Tuesday, December 18, 2012
Anonynomous. (online). http://www. teaching.shu.ac.uk . Access on Tuesday, December
18, 2012
Monica, Maria SBW, dkk.2012.Panduan Praktikum Kimia Analitik III Spektroskopi dan
Kromatografi.Surabaya: UNESA Unipress.
Experiment Result GAS CHROMATOGRAPHY
ATTACHEMNT
Picture Explanation
Gases used in Gas Chromatography
(GC)
Red : H2
Blue : O2
Yellow : N2 gas
Gas Chromatography Instrument
Experiment Result GAS CHROMATOGRAPHY
Signal of detector shown: 75, 9
It is lower than 100. It is mean that
detector is dirty. It can be caused by
condensation or other noise
This spectrum shows that the detector
contain noise, if it is free from noise the
spectrum is straight line.
Inside part of Gas Chromatography
Instrument
Experiment Result GAS CHROMATOGRAPHY