gc-ms

Introduction TO GC-MS: 

Presented By: Mangeshkumar P. Padame Govt college of amravati maNGESH.PHARMA@GMAIL.COM Introduction TO GC-MS GCOP AMRAVATI

Content: 

Content Introduction Principal Instrumentation Working Application Advantages 26/11/2011 2

Introduction: 

Introduction Gas chromatography-mass spectroscopy (GC-MS) is one of the so-called hyphenated analytical technique As the name implies, it is actually two techniques that are combined to form a single method of analyzing mixtures of chemicals Gas chromatography is a technique capable of separating, detecting and partially characterizing the organic compounds particularly when present in small quantity. Mass spectroscopy provides some definite structural information from in small quantity. 26/11/2011 3

Cont… : 

Cont… Combination of GC-MS provides extremely powerful tool because it permits direct and effectively continuous correlation of chromatographic and mass spectroscopic properties The separation and identification of the components of complex natural and synthetic mixture are achieved more quickly than any other technique with less sample 26/11/2011 4

Principle of GC-MS: 

Principle of GC-MS The sample solution is injected into the GC inlet where it is vaporized and swept onto a chromatographic column by the carrier gas (usually helium). The sample flows through the column and the compounds comprising the mixture of interest are separated by virtue of their relative interaction with the coating of the column (stationary phase) and the carrier gas (mobile phase ). The latter part of the column passes through a heated transfer line and ends at the entrance to ion source where compounds eluting from the column are converted to ions. 26/11/2011 5

GC-MS Instrument: 

GC-MS Instrument The insides of the GC-MS, with the column of the gas chromatograph in the oven on the right. 26/11/2011 6

Instrumentation: 

Instrumentation 26/11/2011 7

Instrumentation: 

Instrumentation The GC-MS is composed of two major building blocks: the gas chromatograph and the mass spectrometer The gas chromatograph utilizes a capillary column which depends on the column's dimensions (length, diameter, film thickness) as well as the phase properties . The difference in the chemical properties between different molecules in a mixture will separate the molecules as the sample travels the length of the column. The molecules are retained by the column and then elute (come off of) from the column at different time 26/11/2011 8

Cont..: 

Cont.. This allows the mass spectrometer downstream to capture, ionize, accelerate, deflect, and detect the ionized molecules separately. The mass spectrometer does this by breaking each molecule into ionized fragments and detecting these fragments using their mass to charge ratio. 26/11/2011 9

Samples : 

Samples State Organic compounds must be in solution for injection into the gas chromatograph. The solvent must be volatile and organic (for example, hexane or dichloromethane). Amount Depending on the ionization method, analytical sensitivities of 1 to 100 pg per component are routine. Preparation Sample preparation can range from simply dissolving some of the sample in a suitable solvent to extensive. Clean up procedures using various forms of liquid chromatography. 26/11/2011 10

Types of Ionisation: 

Types of Ionisation Electron impact ionisation Chemical Ionisation 26/11/2011 11

Electron Impact Ionization: 

Electron Impact Ionization A high-energy electron can dislodge an electron from a bond, creating a radical cation (a positive ion with an unpaired e - ). => 26/11/2011 12

Chemical ionisation: 

Chemical ionisation Used to confirm molecular weight. Known as a “soft” ionisation technique. Differs from EI in that molecules are ionised by interaction or collision with ions of a reagent gas rather that with electrons. Common reagent gases used are Methane , Isobutane and Ammonia. Reagent gas is pumped directly into ionisation chamber and electrons from Filament ionise the reagent gas. 26/11/2011 13

Chemical Ionisation(2): 

Chemical Ionisation(2) First - electron ionization of CH 4 : CH 4 + e -  CH 4 + + 2e - Fragmentation forms CH 3 + , CH 2 + , CH + Second - ion-molecule reactions create stable reagent ions: CH 4 + + CH 4  CH 3 + CH 5 + CH 3 + + CH 4  H 2 + C 2 H 5 + CH 5 + and C 2 H 5 + are the dominant methane CI reagent ions 26/11/2011 14

Definition of Terms: 

Definition of Terms Molecular ion The ion obtained by the loss of an electron from the molecule Base peak The most intense peak in the MS, assigned 100% intensity M + Symbol often given to the molecular ion Radical cation + ve charged species with an odd number of electrons Fragment ions Lighter cations formed by the decomposition of the molecular ion. These often correspond to stable carbocations .

Mass Analyzers: 

Mass Analyzers Low resolution Quadrupole Ion trap High resolution TOF time of flight Sector instruments (magnet) Ultra high resolution ICR ion cyclotron resonance 26/11/2011 16

Quadrupole Mass Ion Filter: 

Quadrupole Mass Ion Filter 26/11/2011 17

Ion Trap : 

Ion Trap 26/11/2011 18

Time of Flight -TOF: 

Time of Flight -TOF 26/11/2011 19

PowerPoint Presentation: 

26/11/2011 20

Analysis: 

Analysis A mass spectrometer is typically utilized in one of two ways: Full Scan or Selective Ion Monitoring (SIM). The typical GC/MS instrument is capable of performing both functions either individually or concomitantly, depending on the setup the particular instrument. 26/11/2011 21

Application: 

Application Environmental monitoring and cleanup Criminal forensics Law enforcement Sports anti-doping analysis Food, beverage and perfume analysis Astrochemistry Pharmaceutical Analysis 26/11/2011 22

Pharmacutical Analysis : 

Pharmacutical Analysis Prostaglandins and Thromboxanes Steroids Carbohydrates Lipids Amino Acids and Peptides Plant Product 26/11/2011 23

Limitation: 

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. 26/11/2011 24

Reference: 

Reference Gas chromatography-mass spectroscopy from Wikipedia ,The free encyclopedia. Instrumental methods of Analysis by Willard,Merritt,Dean,Settle,7 th Edition. Handbook of Instrumental Techniques for Analytical Chemistry. 26/11/2011 25

Thank You : 

Quastion Thank You