Sample Spectra 1/1/2019

Sample Spectra 1/1/2019

MALDI TOF MS 1/1/2019

Some simple MS spectra CH3OH by EI methods (a hard Ionization method) 1/1/2019

Some simple MS spectra CH3Br, EI ionization (Hard Ionization) 1/1/2019

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MS Analysis of p-Aminobenzyl Amine Conversion Product 153 – 136= 17 (=NH3)

Tandem Mass Spectroscopy (MS/Ms) 1/1/2019

Description Suppose we analyze a mixture of Components by a soft ionization method (Electron Spray, Chemical ionization). Each component produces characteristic ion species such as [MH]+. The mass spectrum contains peaks for each component. We would like to see structural information for each compontent. 1/1/2019

Description The simplest Tandem mass spectrometer contains two MS. The first mass spectrometer is used to select the a single mass (Precursor) mass which is characteristic of one of the components in the mixture. The selected mass ions pass through a region where they are activated in some way that causes them to fall apart to produce fragment (product) ions. 1/1/2019

Description This is usually done by colliding the ions with a neutral gas in a process called colldining activation (CA) or collision-induced dissociation (CID) . The second mass spectrometer is used to separate the fragment ions according to mass. The ressulting MS/MS spectrum consists only of product ions from the selected precursor. 1/1/2019

Kinds of MS/MS experiments Consider a precursor ion, m1+ that decomposes to produce a product ion, m2+and a neutral loss , N: m1+ m2+ + N MS/MS experiment can be classified according to which of these species is a constant. 1/1/2019

Kinds of MS/MS experiments Product ion scan (m1+ Specified) If we do an MS/MS experiment to find out all of the product ions m2+ that result from the decomposition of a specified parent ion m1+, then this is called product ion scan. This is the most common and well known MS/MS experiment . This is used to determine structurally significant fragment ions for a selected precursor ion. 1/1/2019

Kinds of MS/MS experiments Precursor ion scan (m2+ specified) If we perform an MS/MS experiment that tells us all of the possible ions m1+ that decomposes to a specified parent ions m1+, then this called a product –ion scan. This is useful hen you know that a product (fragment) ion mass is characteristic of a class o compound, and you would like to identify the mixture components that belong to that compound class. 1/1/2019

Kinds of MS/MS experiments Constant neutral loss scan (N specified) An MS/MS experiment that looks for all pairs of precursor ions and product ions that differ by a constant neutral loss, N. then this is called a constant neutral loss scan. This is useful when you know that a particular neutral loss mass is characteristic of a class of compounds and you would like to identify the mixture components that belong to that compound class. 1/1/2019

Samples MS/Ms of Quinine, High Energy CID vs. Low Energy CID 1/1/2019

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MALDI Applications Narrow MMD Hompolymers Broad MMD Homopolymers As a chromatography detector End groups Copolymers Elucidate Polymer structure 1/1/2019

Applications Narrow MMD Hompolymers Already seen for PS Better consistent with results of other methods like light scattering and GPC 1/1/2019

Applications Broad MMD Homopolymers For polymers with PDI> 1.2, it has been shown that the results are not consistent with other methods and are not reproducible as well. Solution: fractionation into narrower PDI is recommended by any of available methods such as sequential precipitation, dissolution or GPC. 1/1/2019

Applications End groups Copolymers Elucidate Polymer structure 1/1/2019

Conclusion MS is a powerful tool for investigation of compounds , small molecules as well as macromolecules including synthetic polymers, natural polymers and biomolecules. This belongs to the complicated instrumental methods. A wide range of methods utilizing sophisticated techniques are developed now useful for many target and detail investigations on macromolecules. Therefore a complete discussion about the all available MS methods is quite out of the scope of the class. 1/1/2019

Exercises Write down all the important notes you have learned from MS. Find one recently published article dealing with the analysis of polymers by using one of the MS methods you have seen up to know in the class. (Individually) 1/1/2019

THE END 1/1/2019