1. PERSENTED TO :- PRESENTED BY:-
MD Abdul Qayum
Shakir
M. Pharm 1st year
2nd sem
GC- AAS
GAS CHROMATOGRAPHY-ATOMIC
ABSORPTION
SPECTROSCOPY
2. • Hyphenated techniques is a combination or coupling of two different analytical
techniques with the help of proper interface.
• Hirschfield (1980) introduced the term “hyphenation” to refer to the combination of a
separation technique and one or more spectroscopic detection techniques.
• The number of existing techniques has been combined to expand the utility .The direct
conjugation of chromatographic technique with spectroscopic examination constitutes
several powerful analytical techniques.
• Hyphenated techniques ranges from the combination of: separation-separation,
separation- identification, and identification-identification techniques.
HYPHENAED TECHNIQUE
3. LIST OF HYPHENATED TECHNIQUES
I. LC-MS LC-API-MS
II. LC-NMR LC-ESI-MS
III.GC-MS LC-NMR-MS
IV.CE-MS ESI-MS-MS
V. GC-NMR LC-PDA-MS
VI.GC-AES HPLC-ICP-AES
VII.GC-AAS
4. of gas chromatography with atomic absorption
This technique is combination
spectroscopy.
GC-AAS
• AAS is one of the elemental analysis techniques.
• GC performs the separation of the components and
with the help of AAS the elemental identification of the
component is performed.
• Elemental composition of every peak separated by GC is determined.
•
• GC effluent is directly introduced into the Quartz atomization furnace
• Analytes are first atomized using microwave irradiation ,
where the atoms are transferred to electronically excited state
5. • Then these electrons are return to the lower energy levels at that time photons are
emitted at certain wavelength that are characteristic of the particular element
• In both the techniques sample is in gas phase so the techniques are complementary to
each other
• An eighth inch steel plate was placed on top of the G.C. to act as an optical table for
the magnetically mounted optical components of the A.A.S. 1/2 inch diameter hole
was drilled through the plate to allow the transfer line and its heater passage.
• The G.C. was directly interfaced to the lower electrode with a stainless steel transfer
line. The transfer line was sealed to the electrode by means of a teflon ferrule which
also served to electrically isolate it from the electrode.
• A chrome1-alumel thermocouple pyrometer was used to monitor the transfer line
temperature. The stainless steel transfer line was later replaced with pyrex capillary
tubing.
7. GC unit
GAS CHROMATOGRAPHY
Carrier gas Flow regulators & Flow Meters Injection devices Columns
Temperature control devices Detectors 8
CARRIER GAS. Requirements of a carrier gas: - • Inertness • Suitable for the
detector • High purity • Easily available • Cheap • Should not cause the risk of
fire • Should give best column performance.
Hydrogen Better thermal. conductivity Disadvantage: it reacts with
unsaturated compounds & inflammable 2. Helium excellent thermal conductivity
it is expensive 3. Nitrogen reduced sensitivity & it is inexpensive
8. Flow regulators & Flow meters. Deliver the gas with uniform pressure/flow
rate - Rota meter & Soap bubble flow meter ✓ Rota meter: - placed before
column inlet it has a glass tube with a float held on to a spring. the level of the
float is determined by the flow rate of carrier gas. ✓ Soap Bubble Meter: -Similar
to Rota meter & instead of a float, soap bubble formed indicates the flow rate.
Injector. Here the sample is volatilized and the resulting gas entrained into the
carrier stream entering the GC column. • Injector Types 1. Split/ Split less
Injector 2. On-Column Injector 3. High Oven Temperature On-Column Injector 4.
Large Volume On-Column Injector 5. Packed Column Injector 6. Purged Packed
Injector 7. Programmable Temperature Vaporizing Injector
9. Split mode. The split vent is open, part of the sample goes into the column. o
When analyzing high concentration or neat samples. o Yields the sharpest peaks
if the split gas is properly mixed. o Standard for capillary columns. Split-less mode
o The split vent is closed, most of the sample go into the column. o When
analyzing low concentration or diluted samples. o Splitless times of ~ 1 minute are
typical. o Standard for capillary columns.
COLUMNS. Column is one of the important parts of GC which decides the
separation efficiency. Columns are made up of glass and stainless steel.
Classification of columns: - Depending on its use: ✓ Analytical column ✓
Preparative column Depending on its nature Column Types: - ✓ Packed column: -
Are available in packed manner commercially and hence are called as Packed
column.
10. Open tubular/ Capillary Column: - They are made up of long capillary tubing of
30-90 meters in length and have diameter of 0.025 to 0.075 cm. These are
made up of stainless steel and are in the form of a coil. The inner wall of the
capillary is coated with stationary phase liquid in the form of a thin film. These
column offer least resistance to the flow of carrier gas and hence they are more
efficient than packed column which offer more resistance to flow of carrier gas.
Monochromators: - Part in an AA spectrophotometer. It is used to separate out
all of the thousands of lines. Without a good monochromator, detection limits are
severely compromised. A monochromator is used to select the specific
wavelength of light which is absorbed by the sample, and to exclude other
wavelengths. The selection of the specific light allows the determination of the
selected element in the presence of others. They are of two types: Prism
monochromator: - Quartz material is used for making prism, as quartz is
transparent over entire region. Grating monochromator: - it consists of a series
of parallel straight lines cut into a plane surface.
11. Detector: - the light selected by the monochromator is directed onto a
detector that is typically a photomultiplier tube, whose function is to convert the
light signal into an electrical signal proportional to the light intensity. The
processing of electrical signal is fulfilled by a signal amplifier. The signal could
be displayed for readout, or further fed into a data station for printout by the
requested format. Photomultiplier Tubes Components
• Made of a glass vacuum tube
• Photocathode
• Several dynodes
• One anode
12. APPLICATIONS
In 1976, NATO Science Committee's Panel on Marine Sciences, in regard to a
sunken cargo ship carrying tetraethyl lead (TEL), concluded that very little is
known of the reactions of TEL and sea water. Speculations of the effects ranged
from "catastrophic" to "no effect." G.C.- A.A. is an ideal method for studying the
kinetics of TEL in sea water. 2. A study of leaded gasolines was first chosen to
demonstrate the usefulness of the techniques. The G.C.- A.A. can also be used
for air sampling analysis, where air samples are trapped out in a cold trap or on
an adsorbent and placed in the G.C. A large portion of atmospheric molecular
lead pollution is attributed to evaporating gasoline. A simple experiment was
designed to determine lead concentrations in evaporating gasoline.
13. Quality control. and analysis of drug products like antibiotics(penicillin
G), antivirals (amantidine) , general-anaesthetics (chloroform , ether),
sedatives/hypnotics(barbiturates) Penicillin G Amantidine Chloroform
Barbiturates
Assay of drugs. purity of a compound can be determined for example
drugs like atropine sulphate, clove oil, stearic acid. Atropine Sulphate
Eugenol Stearic Acid
In determining. the levels of metabolites in body fluids like plasma,
serum, urine. Analysis of foods like carbohydrates, proteins, lipids,
vitamins, steroids, drug and pesticides residues. Dairy product analysis
like milk, butter-for detection of aldehydes, milk sugars, ketones and fatty
acids. Separation and identification of volatile materials, plastics, natural
and synthetic polymers, paints and microbiological samples.
14. GC-AAS is main tool used in sports anti doping laboratories to test athletes
urine samples for prohibited performance enhancing drugs. EG : anabolic
steroids. Impurity profiling of pharmaceuticals. Model impurity profiling: gc-aas
trace of commercial sample of propranolol with impurities.
GC-AAS is becoming the tool of choice for tracking organic pollutants in the
environment. Identification of drugs of abuse & metabolites of drugs of abuse
in blood, urine & saliva.The G.C.-A.A. system is very sensitive and extremely
selective and is ideal for monitoring volatile metal compounds.
