 Once again it is my pleasure to welcome you all to MSP lecture series on interpretive spectroscopy. Let me continue discussion on mass spectrometry. In my last lecture I was discussing about the mass spectrum of crown ether. I showed you here and also I showed you how to arrive at the name of a crown ether here. This is 18 crown 6 eth this one. So we have 6 oxen atoms are there. It is ideally suited to accommodate a metal ion with a cahedral geometry. So in this one the molecular ion peak is 264. From this one it loses a 43 mass corresponds to C2H3O to give this peak with a molecular value of 221 and then again it incrementally it loses 44 that is due to C2H4O mighty and regularly until it arrives at this last one with a mz value of m by z value of 45 that is C2H4OH plus. That means wherever we have this CH2O mighties one can see the fragmentation follows this sequence here. Now let us look into metal carbonyls. We come across a large number of metal carbonyls in the simple mononuclear to polynuclear clusters and cages. For example here how to look into the spectrum how to get information extracted from mass spectra of metal carbonyls and of course we all know the fact that metal carbonyls are relatively more volatile and provides spectra which may be easily interpreted. The fragmentation process involves the loss of carbonyl ligands in the form of carbon monoxide gas that means you can clearly distinguish between the parents from the parent peak to the bunches of peaks we will see here with gradation of a CO means about 28 mass loss. So this is a electron impact mass spectrum of dihydride osmium triosminium CO10 and it is originated from OS3 CO12. So from this one two carbon monoxide have been eliminated and H2 has come. So if H2 is written like this you should assume this is neutral H2 binding is there in this fashion and in case if they have written something like this this is hydride and osmium will be in the plus two state let's assume it is in zero valence state here. This was taken from this article appeared in JAX in 1988 and the fragmentation pattern you can see here initially after bombardment it generates a parent peak a cation radical and then the gradation is there for example M-1 CO goes until we get the metal ion with all the carbon monoxide being stripped off. This EI provides accurate mass information for polynuclear metal carbonates and pyrolysis of OS3 CO12 produces a range of higher nuclearity clusters and OS5 C CO15, OS6 CO18 and OS7 CO21 and OS8 CO23. This is how higher analogs are made starting from the simplest one such as OSCO5 or OS3 CO12 and similarly in case of iron we use Fe CO5 and from that one we can make Fe2 CO9 and Fe3 CO12 and so on and they are known for undergoing disproportionation reaction to form high nuclearity clusters and from the clusters apart from the parent peak molecular ion we can also see the loss of CO and until it hits the naked metal ion. So EI mass spectrometry provides correct molecular formula for these compounds and also it can give information about the presence of industrial atoms carbides in this case. As I mentioned on heating thermally pyrolysis means heating at high temperature carbon monoxide comes out and in that process what happens one or two carbon atoms can also go to the industrial and form carbides in that case the presence of carbon can also be identified using mass spectrum here that is the advantage of mass spectrum here. Other techniques such as element analysis IR, NMR spectroscopy are unable to provide this information for example if carbon carbon monoxide degrades to give a carbide unit that is in the cluster so in that it is very difficult to extract that information from other techniques apart from x-ray crystallography it's difficult for IR, NMR cannot really tell about this vital information from that point of view mass spectrometry is very very important in case of organometallic compounds. So here I have shown for ferrocene the ferrocene cation is there here a radical and then here we have the loss of 1 C5H5 we get this one and eventually other Cp group is also lost to get Fp2 this is pretty simple and Ea mass spectrum of ferrocene showing high abundance of molecular ion the base peak is 121 here this is the one this one accounts for Cp Fp+. So now this is for cobaltrysacetate again base peak is there here and then with loss of methyl group it comes here again loss of methyl group so you can see here 100% peak is here and the corresponding ones are shown here. So now let us look into some other spectrum meters we use in case of mass one such instrument for high molecular weight measurement is Maldi TOF mass spectrometry that means matrix assisted laser desorption ionization time of flight mass spectrometry quite lengthy but it is abbreviated as Maldi TOF MS and this is commonly used MS mass technique. Maldi is a soft ionization technique unlike Ea to create ions with minimal fragmentation by using a laser energy and in TOF the protonated ions are accelerated by an electric field to make an ion to attain the kinetic energy as any other ions having the same charge the velocity of the ion depends on the MZ ratio and the time that takes for the ion to reach the detector where it is measured. So Maldi TOF mass spectrometry can analyze a wide variety of biomolecules including peptides and carbohydrates that means the advantage is this one is you can go for higher molecular weight complex molecules such as peptides and carbohydrates and the another one is triple quadrupole mass spectrometry and this is abbreviated as TQMS or QAQ it is a tandem mass spectrometer in which the first and third quadrupole act as mass filters and the second act as collision cell to fragment the selected precursor or parent ions and to generate fragment or daughter ions. TQMS is widely used tandem MS and is relatively simple and easy to use with good reproducibility to offer various applications at a very low cost and the TQMS can be used for structural oxidation that can provide information about fragmentation patterns also very useful quantitative studies also one can take up with this instrument due to increased sensitivity and specific yielding lower detection and quantification limits. TQMS is a vital option for many areas such as pharmaceutical development, clinical research and environmental studies and so on where quantification is the prime objective when they are characterized. Next one is quadrupole trap mass spectrometry is a hybrid triple mass spectrometer different from classical triple quadrupole mass spectrometry the Q3 as also known as can work as either a standard quadrupole mass filter or a linear ion trap LIT with higher sensitivity with traditional 3D ion trap this instrument retains the classical triple quadrupole scan functions and also it can be used for sensitive ion trap experiments. Then there is one more hybrid linear ion trap orbit trap mass spectrometry so this one combines a linear ion trap and high resolution orbit trap is one of the tandem mass spectrometers in use today LIT uses a set of quadrupole rods to confine ions radially and a static electrical potential on the end electrodes to confine the ions axially so orbit trap consists of an axially symmetrical mass analyzer that makes ions move in an orbital motion around the spindle. Then the image current is detected and converted into a mass spectrum by the Fourier transform this hybrid mass spectrometry is widely used in protomics and metabolomics analysis so this is where its role comes into picture and the other one is quadrupole orbit trap mass spectrometry combines high performance quadrupole precursor selection with high resolution accurate mass orbit trap detection the first mass analyzer is a quadrupole and the second is a high resolution orbit trap it can be widely used in various fields like protomics, metabolomics, food safety, toxicology and so on very specially designed for very special purposes these ones may not be needed for routine examination of molecules that are generated in chemistry laboratories and then how to choose an ionization technique we have several ionization techniques are there so that usually depends upon what information is required from mass spectrometry analysis and based on that one one can choose an appropriate ionization technique for example a hard ionization method such as electron impact may be used for a complex molecule in order to determine the component parts by fragmentation if the molecule itself is complex and if you are not getting molecular ion peak then we have to use hard ionization like electron impact in that case what happens fragmentation is very high in that case by looking into different fragmentations we can assemble we can get back into the constituent molecule from which it is formed so on the other hand a high molecular weight sample of polymer or protein may require an ionization method such as Maldi because electron impact we know that we cannot go beyond 1000 molecular weight but if the compounds or samples have high molecular weight then Maldi is an ideal in order to so often samples may be easily analyzed using multiple ionization methods and the choice is simplified to choosing the most convenient method for example electro spray ionization may be easily coupled to liquid chromatography systems as no additional sample preparation is required so that means they have some flexibility of combining with more or one or more other devices for further studies and analysis and separation so here I have given a table information we are looking for and also the ionization technique one should use based on what we are looking for elemental analysis simple element analysis if you want to know composition inductive coupled plasma is used in typical elemental analysis instrument micro analysis this is what is used and the depth profiling first atom bombardment fab secondary ion mass spectroscopy and then chemical speciation component analysis we should go for electron impact and molecular species identification of compounds soluble in common solvents ideal one is electro spray ionization and molecular species identification of hydrocarbon compounds field ionization molecular species identification of high molecular weight compounds matrix assisted laser desorption ionization Maldi and then molecular species identification of halogen containing compounds the best one is ideally suited chemical ionization the negative mode so I think this much will be good enough whatever the information desired is listed on left side and then appropriate ionization technique that has to be used or employed is also given here so it would give some information about the device we should look for and an electron ionization mass spectrum does not show neutral species and radicals and their mass may be obtained from the mass difference between analyte and product ion for example what we don't get the molecular ion peak in that case what happens we should look for the fragments and also the mass difference from that one we should be able to identify the sample molecular weight so ion sources in gas wave method as I mentioned we use electron ionization chemical ionization direct analysis in real time inductively coupled plasma matrix assisted laser desorption ionization Maldi fast atom bombardment FAB a thermal ionization sources plasma ionization this is in case of analysis so these are the ion sources used in gas phase methods now let us try to be familiar with some of the terms so I have given the glossary of terms here that is used in mass spectrometry CI chemical ionization reagent ions generated in situ so when we bombard with electron fast moving electrons generated in situ are used to ionize the molecules through transfer of a proton electron or other charged species from one species to another one this is what exactly happens in the method chemical ionization in electron ionization electron impact is also called electron impact an energetic beam of electrons interacts with sample and ionizes gas phase molecules and electro spray ionization ions are transported into the gas phase by spraying a solution through a capillary at high potential solvent is operated by heating or by a warm bath gas so this is ESI electron spray ionization then FAB fast atom bombardment a fast moving beam of inert gas atoms dissolves ions dissolved in a liquid matrix also one can see for this one LC IMS so GCMS is gas chromatography mass spectrometry a spectrometer with an EI or CI source is used as a detector for a gas chromatography column a very powerful technique for the analysis of complex volatile mixtures that means it is basically it separates and identifies by giving the proper molecular ion value and ICPMS this inductively coupled plasma mass spectrometry a sample is entertained in a flow of gas and carried into a high temperature plasma where it is converted into monatomic ions this is called ICPMS and then the LCMS liquid chromatography mass spectrometry again it is very similar to GCMS a mass spectrometer with ESI or APCL source is used as a detector for a high performance liquid chromatography HPLC is called high performance liquid chromatography a very powerful technique for the analysis of complex mixtures of soluble polar compounds and eventually HPLC one can also separate those compounds and then LSIMS that is called liquid secondary ion mass spectrometry an energetic beam of ions strikes a liquid matrix in which the analyte is dissolved ejecting secondary ions into the gas phase closely related to fab this method is very much similar to fab and then the Maldi I already explained matrix assisted laser desorption ionization a solid matrix co-crystallized with a small amount of analyte is ablated by a laser the matrix absorbs most of the energy and is vaporized to form an energetic in which analyte is ionized and hence we get the information in the detector then M by Z very very important term mass to charge ratio this is a dimensionless quantity obtained by dividing the mass of an ion by the number of charges it carries alternatively no this is nothing ignore this one SIMS is called secondary ion mass spectrometry a fast moving ion beam is used to upgrade a surface removing and ionizing material conditions may be set in such a way as to obtain a depth profile about the sample for which we are performing this experiment I think let me stop here maybe continue in my next lecture I would start discussion on EPR or ESR electron paramagnetic resonance or electron spin resonance and once of that is completed in 3 or 4 lectures I would come back again to look into problems initially related with NMR and then probably IR and mass and then having problems with combination of all these entities until then have an excellent time thank you.