Gc ms(mr.s)

03/05/2023VIKAS COLLEGE OF PHARMACY

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GC-MS TECHNIQUE & ITS APPLICATION

BY @@@ Mr.S @@@ Pharmaceutical Analysis & Quality Assurance, Vikas College Of Pharmacy, Vissannapeta.


2 CONTENTS Introduction Gas Chromatography Interface Mass Spectrometry Data Systems Instrumentation New Advances in GC-MS Applications Limitations Conclusion


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Gas ChromatographyIt separates components of sample

InterfaceCombines both techniques by removing pressure incompatibility problem between GC and MS

Mass spectrometryIonise eluted component and separate, identify it according to its mass to charge ratio

INTRODUCTION GC-MS is an integrated composite analysis Instrument Combining GC which is excellent in its ability for separation with mass spectrometry ideal in identification and elucidate structure of separated component .


4 GAS CHROMATOGRAPHY Gas chromatography leads to Separation of volatile

organic compounds

Separation occurs as a result of unique equilibrium established between the solutes and the stationary phase (the GC column)

An inert carrier gas carries the solutes through the column


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GC TRACE OF A THREE COMPONENT MIXTURE. THE MASS SPECTROMETER GIVES A SPECTRUM FOR EACH COMPONENT


7 INTERFACE The pressure incompatibility problem between GC and MS was solved by

Inserting an Interface. Interface join GC with MS. There are many interfaces like jet ,Electrospray,

thermo spray, direct electrical ionization, moving wire or belt interface. Commercially available interface are:

Jet Interface device takes advantage of the differences in diffusibility between the carrier gas

and the organic compound. These jet separators work well at the higher carrier gas flow rates (10 to 40

mL/min)Direct Interface Most GC-MS interfacing is now done by simply inserting the capillary column directly

into the ion source. This gives a helium or hydrogen GC carrier gas velocity of 25 to 35 cm/sec or a flow of

about 1 to 2 mL/min.


8 MASS SPECTROMETER Mass spectrometry is a technique used for

measuring the molecular weight and determining the molecular formula of an organic compound

In general a mass spectrometer consists of an ion source, High-vacuum system a mass-selective analyzer, and an ion collector


9 SCHEMATIC DIAGRAM OF MS


10 MASS SPECTRUM OF METHANE


11 DATA SYSTEM GCMS system purchased with a powerful (but small) computer

acting as a data system. Data System of GC-MS used to identify and measure the

concentration of one or more analytes in a complex mixture. Quantitation can be based on peak areas

mass chromatograms Selected Ion Monitoring(SIM).

With the selected ion monitoring technique, the mass spectrometer is not scanned over all masses; instead, the instrument jumps from one selected mass to another.


12 INSTRUMENTATION

Gas Chromatography Interface Mass Spectoscopy


13 GAS CHROMATOGRAPHY Carrier Gas Injectors GC Columns Stationary Phase Detectors


14 CARRIER GASPROPERTIES OF CARRIER GAS1. Highly pure (> 99.9%)2. Inert so that no reaction with stationary phase or

instrumental components can take place, especially at high temperatures.

3. A higher density (larger viscosity) carrier gas is preferred.

4. Compatible with the detector since some detectors require the use of a specific carrier gas.

5. A cheap and available carrier gas is an advantage.


15 INJECTORS Septum type injectors are the most common.

These are composed of a glass tube where vaporization of the sample takes place.

The sample is introduced into the injector through a self-sealing silicone rubber septum.

The carrier gas flows through the injector carrying vaporized solutes.

The temperature of the injector should be adjusted so that flash vaporization of all solutes occurs.


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17 GC COLUMNS & STATIONARY PHASE These columns are fabricated from glass, stainless

steel, copper, or other suitable tubes. Stainless steel is the most common tubing used with

internal diameters from 1-4 mm. The column is packed with finely divided particles

(<100-300 mm diameter), which is coated with stationary phase.

However, glass tubes are also used for large-scale separations.


18 DETECTORS Simple and reliable Sensitive (10-15 g/s) to electronegative groups

(halogens) Largely non-destructive Insensitive to amines, alcohols and hydrocarbons Limited dynamic range (102) Mass sensitive detectors Thermal Conductivity Detector (TCD) Flame Ionization Detector (FID) Electron Capture Detector (ECD)


19 FLAME IONIZATION DETECTOR This is one of the most sensitive and reliable destructive

detectors. Separate two gas cylinders, one for fuel and the other for O2 or air are used in the ignition of the flame of the FID.

The FID detector is a mass sensitive detector where solutes are ionized in the flame and electrons emitted are attracted by a positive electrode, where a current is obtained.

The FID detector is not responsive to air, water, carbon disulfide. This is an extremely important advantage where volatile solutes present in water matrix can be easily analyzed without any pretreatment.


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FLAME IONIZATION DETECTOR


21INTERFACE

The pressure incompatibility problem between GC and MS was solved by Inserting an Interface.

Interface join GC with MS. There are many interfaces like jet ,Electronspray, thermo spray, direct electrical ionization, moving wire or belt interface.

Commercially available interface are: * JET INTERFACE * DIRECT INTERFACE


22 MASS SPECTROMETERMain components of the mass spectrometer

- Sample input system

- Ionization source

- Mass analyzer

- Detector


23 SAMPLE INPUT METHODSGas Expansion

- Useful for gas samples and liquids with sufficiently high vapor pressures

- The gas or vapor expands into an evacuated and heated vessel

- Sample leaks through holes in a gold foil seal into the ionization source (termed molecular leak inlet)

- Pressure in ionization is maintained at 10-6 – 10-8 torr


24 IONIZATION SOURCES The sources which are used separate the sample

into individual ions through the bombardment technique are called as “ionization sources.”

Several types of ionization sources are available such as follows

* Electron Ionization * Chemical Ionization * Atmospheric Pressure Ionization * Desortion Ionization etc…..,


25 ELECTRON IONIZATION (EI) - Commonly used for analysis of organic samples

- Electrons are emitted from a heated tungsten filament cathode

- Electrons are accelerated towards the anode with a potential of about 50 – 100 V

- Electrons meet at right angles with the sample molecules.


26 MASS ANALYSERFUNCTIONS

– 1.Differentiates ions according to their m/z-2. Different designs are available

SCANNING INSTRUMENTS - Only ions of a given m/z pass through the analyzer at a given time

- Magnetic Sector Mass Analyzer

- Quadrapole Mass Analyzer


27 TIME OF FLIGHT (TOF) ANALYZER

- Makes use of a drift tube

- Pulses of ions are accelerated into the an evacuated drift tube (free of field or external force)

- Velocity of an ion depends on m/z (depends on mass if all ions have the same charge)

- Lighter ions move faster along the tube than heavier ions

- Ions are separated in the drift tube according to their velocities (v)


28 DETECTORSMeasure one m/z value at a time (single channel

detectors). Multiple detectors are used for multiple ion detection.

High resolution magnetic sector instruments use multiple detectors called multi-collectors. -Electron multiplier detector

-Faraday cup detector -Array detectors


29 ELECTRON MULTIPLIER (EM) DETECTOR

- The most common detector in MS for ions

- Similar to PMT

- Very sensitive and has fast response


30 SCHEMATIC DIAGRAM OF GC-MS


31 NEW ADVANCES IN GC-MS

Gas chromatography coupled to tandem mass spectrometry(GC/MS/MS) is used to separate organic compounds in the mixture.

Ms/Ms is highly selective mass spectrometric technique, target analytes are detected regardless of the sample matrix.

These selected precursor ions or parent ions are induced to further dissociate by collision with helium molecules.


32 This increased selectivity of MS/MS also results in an enhancement of signal to noise ; thus somewhat lower limits of detection are achieved . GC/MS/MS provides unequivocal identificationin cases where GC/MS spectra of compounds are difficult to interpret.


33 APPLICATIONS OF GC-MS

Petrochemical and hydrocarbons analysis Geochemical research Forensic (arson, explosives, drugs, unknowns) Environmental analysis Pesticide analysis, food safety and quality Pharmaceutical and drug analysis


34 APPLICATIONS OF GC-MS

Clinical toxicology Food and fragrance GC-MS is increasingly used for detection of

illegal narcotics marijuana, cocaine, opioids Clinicians oxycodone and oxymorphone

Sports anti-doping analysis


35 LIMITATION Only compounds with vapor pressures exceeding about 10–10 torr

can be analyzed by gas chromatography-mass spectrometry (GC-MS).

Determining positional substitution on aromatic rings is often difficult.

Certain isomeric compounds cannot be distinguished by mass spectrometry (for example, naphthalene versus azulene), but they can often be separated chromatographically.


36 CONCLUION

As we can see, GC-MS is used both in qualitative and quantitative measurement. Nowadays the cost is also cheaper than before as quadrupole and ion trap instruments are used. The recent trend has been to produce smaller and smaller instruments. It does not only save space but also save manufacturing cost. Modern instruments are often equipped with automatic injection system and once filled the data system can control all functions of the instruments including sample introduction. So the instrument will almost run itself.


37 REFERENCES R. S. Gohlke, Analytical Chemistry, 31 (1959), 535–41. J. T. Watson and K. Biemann, Analytical Chemistry, 37 (1965),

844–51. R. Ryhage, Analytical Chemistry, 36 (1964), 759–64. T. E. Jensen and others, Analytical Chemistry, 54 (1982), 2388–

90. R. A. Hites and K. Biemann, Analytical Chemistry, 40 (1968),

1217–21. R. A. Hites and K. Biemann, Analytical Chemistry, 42 (1970),

855–60.


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Gc ms(mr.s)