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MAEERS MAHARASHTRA INSTITUTE OF PHARMACY, PUNEASEMINAR ON MASS SPECTROMETRYAs per Pune University syllabus 1st semester Presented By: Mr. Patil Somnath Ashok

Guided By: Principal Dr. B.S. Kuchekar1CONTENTS:IntroductionDefinitionClassification Atomic MS Molecular MSPrinciple of MSInstrumentation Ion sources Mass analyzers Detectors Vacuum system Applications

2Introduction: In Mass Spectroscopy (MS), atomic and molecular weights are generally expressed in terms of atomic mass units (amu). The atomic mass unit is based upon a relative scale in which the reference is the carbon isotope 12C6, which is assigned a mass of exactly 12 amu. Thus the amu is defined as 1/12 of the mass of one neutral carbon atom. 3Mass SpectroscopyMass spectroscopy is perhaps one of the most widely applicable of all the analytical tools available to the analytical chemist in the sense that this technique is capable of providing information about :4the qualitative and quantitative composition of both organic and inorganic analytes in complex mixturesthis instrument measures compounds with molecular masses up to 200, 000 Daltons.the structures of a wide variety of complex molecular species isotopic ratios of atoms in samples andthe structure and composition of solid surfaces.5Mass SpectroscopyMolecular Mass Spectroscopy Atomic Mass Spectroscopy 6Atomic Mass SpectrometryNearly all elements in the periodic table can be determined by mass spectrometryMore selective and sensitive than optical instrumentsSimple spectraIsotope ratiosMuch more expensive instrumentation7Atomic MassSpectrometry (Inorganic MS)

Mass Spectrometers ICP-MS Spark Source MS Glow-Discharge MS Elemental Surface Analysis by MS Laser Ablation ICP-MS8Atomic Mass Spectrometry processes:

Atomization (sample intro) Conversion to ions Separation based on m/z ratio Detection

In other forms of MS (GC-MS or MS of organic compounds), sample introduction does not involve making atoms, just getting molecules into the high vacuum system9Advantages of Atomic Mass Spectrometry over Optical Atomic Spectrometry:1) Detection limits are better, sometimes several orders of magnitude 2) Very simple spectra3) Ability to measure isotope ratiosDisadvantages:1) Equipment cost2) Instrument drift3) Isotopic interferences10

Advances In Atomic Mass Spectrometry

11Molecular Mass Spectroscopy 12PrincipleMol. Are bombarded with a beam of energetic electron

Ionization of mol. & fragmentation

Some of which are +ve

Each ion has a particular ratio of mass to charge i.e. m/e ratio

For most of ion charge is 1

So m/e =mol. Wt of ion. 13Mass SpectrometryIt subjects vaporized molecules to bombardment by a stream of high-energy electrons, converting these molecules to ionsThese ions are then accelerated in an electric fieldThe accelerated ions are then separated according to their mass-to-charge ratio in a magnetic or electric fieldThe ions that have a particular mass-to-charge ratio are then detected by a device that counts the number of ions striking it.Simplest form of mass spectrometer performs 4 essential functions: (under vacuum 10-6 mm Hg)14Positive or Negative Ion Mode?If the sample has functional groups that readily accept H+ (such as amide and amino groups found in peptides and proteins) then positive ion detection is used-PROTEINS

If a sample has functional groups that readily lose a proton (such as carboxylic acids and hydroxyls as found in nucleic acids and sugars) then negative ion detection is used-DNA15INSTRUMENTATION:System InletIon SourceMass AnalyzerDetectorVacuumSystem

Signal processorm/z10-5 to 10-8 TorrMASS SPECTROMETER16Instrumentation available:

VG Analytical 70-250-SE Normal geometry double focusing MS. Micromass TofSpec2E Reflectron MALDI-TOFMS. ThermoQuest TraceMS Single quadrupole GC-MS. Bruker ApexIII FT-ICR-MS. ThermoBioAnalysis Dynamo Linear MALDI-TOFMS. Micromass Platform II Open access single quadrupole MS. Waters ZMD Open access single quadrupole MS. ThermoQuest TraceMS Open access single quadrupole GC-MS. ThermoFinnigan LCQ Ion trap. Micromass Platform II Single quadrupole MS

17Resolution & Resolving PowerWidth of peak indicates the resolution of the MS instrument

The better the resolution or resolving power, the better the instrument and the better the mass accuracyResolving power is defined as:

M is the mass number of the observed mass (DM) is the difference between two masses that can be separated

18 MM 25262728293031323334353637383940414243444546474849mass0100%36.5e.g. the mass spectrum of HCl19

20 Sample Introduction:

All Glass Heated Inlet System (AGHIS): Direct Insertion Probe (DIP):MALDI patternDirect Inlets:Gas chromatography columnAPI interfaceGC, HPLC, 21The Sample Inlet System Batch Inlet Systems:

simplest and involve volatilization of liquid For gases, introduced into the metering volume container and expanded into the reservoir flask

The Direct Probe Inlet:

used for solids and non-volatile liquids

sample is introduced by means of a sample holder, or probe,

the amount of the sample to be analyzed is small. 222. IONISATION SOURCES CLASSIFICATION:

GAS PHASE ION SOURCE: HARD SOURCE: DESORPTION ION SOURCE: SOFT SOURCE:

23Gas Phase:Electron ionization (EI)Chemical ionization (CI)Field Ionization (FI)Desorption Field Desorption (FD)Fast Atom Bombardment (FAB)Secondary Ion Mass Spectrometry (SIMS)Laser Desorption (LD)Plasma Desorption (PD)Thermal DesorptionThermo spray ionization (TS)Electrospray (ES)

24Gas-Phase Sources Gas-phase sources require volatilization of the sample before ionization and thus are limited to thermally stable compounds that have boiling points less than about 500C.25

ELECTRON-IMPACT SOURCEIon sources for gases:26Electron Impact Source : In the sources, electrons emitted from a filament are accelerated by a potential of about 70 V and made to collide with gaseous atoms or molecules of the sample causing ionization. Electron-impact ionization is not very efficient and only about one molecule in a million undergoes the primary reaction M + e- = M.+ + 2e-27Electron ImpactAdvantagesWell-EstablishedFragmentation LibrariesInsoluble SamplesInterface to GCNon-Polar Samples

DisadvantagesParent IdentificationNeed Volatile SampleNeed Thermal StabilityNo Interface to LCLow Mass Compounds (20,000 in some models)High Accuracy (