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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.


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:


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.


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


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


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


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


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)


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


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.


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.


http://www.teaching.shu.ac.uk/

http://en.wikipedia.org/Gas_chromatography

ATTACHEMNT

Picture Explanation

Gases used in Gas Chromatography

(GC)

Red : H2

Blue : O2

Yellow : N2 gas

Gas Chromatography Instrument


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


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