66218 - Mass Spectrometry with Exercises

Learning outcomes

When positively evaluated at the end of the course, the student can interpret the mass spectrum af the main families of organic compounds as obtained by electron ionization and can recognize the characteristics of those mass spectra obtained by other ionization techniques.

As to the mass spectrometer, the student knows how sources, ion analyzers, detectors, vacuum pumps operate and their application to analytical problems.

Course contents

Prerequisites.

Optimal conditions for the use of the lessons and the student's examination are a good knowledge of arithmetic, stoichiometry, general chemistry, organic chemistry and, for students whose mother tongue is not Italian, also the knowledge of Italian at level C1.

Modules 1 and 2 are required in e-learning mode [https://www.unibo.it/it/servizi-e-opportunita/salute-e-assistenza/salute-e-sicurezza/sicurezza-e-salute-nei-luoghi-di-studio-e-tirocinio] and participation in Module 3 of specific training on safety and health in the workplace. Information on the dates and methods of attendance of Module 3 can be found in the appropriate section of the course website.

Program.

The course is carried out completely in the classroom; it begins with exercises on the interpretation of mass spectra obtained by electron ionization (24 hours, 2 CFU); continues and ends with lectures on the operating principles of mass spectrometers and their applications (32 hours, 4 CFU).

a) Classroom exercises (24 hours - 2 CFU).

1. Characteristics of an electron ionization (EI) mass spectrum, its representation, technical terms.
2. Procedure for interpreting a mass spectrum EI. Ions with odd and even electron numbers (radical-cations, cations). Molecular ion identification. Factors influencing ionic abundance. Even-electron rule. Stevenson's rule with exceptions. Gamma-Hydrogen rearrangement. H-rearrangement and McLafferty. Multiple rearrangements (examples: phthalates, tributyl phosphate). Examples of EI mass spectra of the main classes of organic molecules; compounds containing fluorine, chlorine and bromine. Identification of unknown mass spectra.
3. Search in NIST library for unknown mass spectra (criteria for comparing unknown spectra with those of the library).
4. Examples of procedures for the solution by GC/MS of real problems of analytical chemistry.

b) Lectures (32 hours - 4 CFU).

1. Why mass spectrometry should be studied: the concrete reasons why the student must be motivated to study mass spectrometry are exposed. Applications and general principles. Representation of a mass spectrum. Definitions of average-, nominal-, monoisotopic-, exact mass. Resolution. Accuracy. Isotopic ions (A+2 rule): example of bromobenzene.
2. Ion sources. Electron ionization (EI). Chemical ionization (CI). Field Ionization (FI). Field Desorption (FD). Fast Atom Bombardment (FAB). Continuous Flow FAB. Matrix Assisted Laser Desorption Ionization (MALDI): structure of the main matrices, calibrating spectra, spectra resolution, monoisotopic masses and mean masses, adduct ions, cationized ions, multicharge ions. ThermoSpray Ionization (TSP). Electrospray Ionization (ESI) (recognition of multi-charge ions and methods of calculating the number of charges). Atmospheric Pressure Chemical Ionization (APCI). Particle Beam (PB). Inductively Coupled Plasma Ionization (ICP). Examples of mass spectra where appropriate.
3. Ion analyzers. Magnetic analyzer (B): equation of motion of an ion, resolution, metastable ions. Electrostatic analyzer (E): equation of motion of an ion. Energy and spatial dispersion. EB and BE double-focus instruments. Ghosts IKE and MIKE. Resolution: definitions, high and low resolution. Linked scan B/E, B²/E, [B2(1-E)]/E². Quadrupole analyzer (Q): equation of motion of an ion, Mathieu diagram for a two-dimensional quadrupole. Multipole Rf-only guides. Tandem Mass Spectrometry (MS²) with triple quadrupole (QQQ) analyzers. Ion trap analyzer (ITMS): equations of motion of an ion, Mathieu diagram for ion trap, ion analysis for resonant ejection, instability ejection. MS² and MSⁿ in ITMS by means of resonant ejection. Use of the ion trap as an ion source and analyzer. Automatic control of the emission intensity of the filament for electron ionization (automatic gain control). Time-of-Flight (TOF) Analyzer: Equation of Motion of an Ion, Delayed Extraction (DE), Reflectron (R), Post Source Decay (PSD). Outline of Ion Cyclotrone Resonance (ICR) and Orbitrap.
4. Gas chromatography/mass spectrometry (GC/MS) and Liquid chromatography/Mass Spectrometry (LC/MS) couplings.

Readings/Bibliography

E. de Hoffmann, V. Stroobant, Mass Spectrometry – Principles and Applications, Third Edition, Wiley, 2007. (*)

T.A. Lee, A Beginner's Guide to Mass Spectral Interpretation, Wiley, 1998. (*)

F. W. McLafferty, F. Turecek, Interpretation of Mass Spectra, University Science Books, Fourth Edition, 1993. (°)

J. H. Gross, Mass Spectrometry – A textbook, Springer, Second Edition, 2011. (^)

J. T. Watson, O. D. Sparkman, Introduction to Mass Spectrometry – Instrumentation, Applications and Strategies for Data Interpretation, Wiley, Fourth Edition, 2007. (^)

R. E. March, J. F. J. Todd, Practical Aspects of Trapped IonMass Spectrometry, Volume V, Applications of Ion Trapping Devices, pp 491-507, CRC Press, 2010. (^)

O. D. Sparkman, Z. E. Penton, F. G. Kitson, Gas Chromatography and Mass Spectrometry – A Practical Guide, Academic Press, Second Edition, 2011. (^)

M. C. McMaster, LC/MS – A Practical User's Guide, Wiley, 2005. (^)

R. B. Cole, Electrospray and MALDI Mass Spectrometry – Fundamentals, Instrumentation, Practicalities, and Biological Applications, Wiley, Second Edition, 2010. (^)

(*) Necessary: it contains all the parts (and much more) that must be studied in order to pass the exam.

(°) Recommended: it contains some parts (and much more) useful for passing the exam.

(^) Not required to pass the exam. Useful for further information, even in the future.

Teaching methods

The course consists of 32 hours of lectures and 24 hours of classroom exercises.

During the lectures the following are explained: (a) theory, instrumentation and applications of mass spectrometry (fundamental principles, representations of the mass spectrum, ionization and ion separation techniques, detectors); (b) procedures for interpreting mass spectra of organic molecules obtained by electron ionization and other techniques.

During the exercises, students learn the rules for interpreting EI spectra and the characteristics of EI spectra of the main classes of substances. They also learn the characteristics of the spectra obtained by ionization CI, MALDI and ESI.

The teaching tools are the blackboard and, to a lesser extent, PowerPoint.

The teaching source is the textbooks recommended above and a few dozen EI mass spectra selected by the teacher and interpreted in the classroom.

The topics of the lessons, the mass spectra and any other material discussed in the classroom or considered useful for study and in-depth study are uploaded to Virtuale (the Unibo repository) after the individual lessons or exercises. Regular consultation is recommended.

 

Assessment methods

The exam is carried out in written form on EOL, in presence, in the computer room, on a PC made available by Unibo. The consultation of texts, notes, internet and fellow students is not authorized. Familiarization with the platform and the PC is left to the student's initiative.

Exam duration: 90 minutes.

View the opening and closing date of registrations on Almaesami - it is not possible to register after the deadline.

Exams.

The exam focuses on the interpretation of 2 EI mass spectra of the type discussed in the classroom (Part A, 15 points available) and on 5 multiple choice questions, only one of which is correct (10 points available) and 1 or 2 open-ended questions (20 points available) on the instrumental and theoretical aspects of mass spectrometry (Part B, a total of 30 points available). The maximum score of the two parts is proportional to their credits (Part A, exercises, 2 CFU, 15 points; part B, lectures, 4 CFU, 30 points). Part A is preparatory to part B. Part B will not be corrected if Part A is insufficient. Both parts must be sufficient to pass the exam.

To answer part A, the student writes on his or her own paper, which he uploads to EOL, after scanning it with his smartphone and saving it as a pdf.

To answer Part B, the student can proceed as above or can type directly on EOL.

Final grade.

The final grade is given by the sum of the points obtained, expressed in thirtieths.

The points of Part A (interpretation of the EI mass spectra) are assigned by dividing the maximum score (15 points) by the number of ions to be interpreted. Zero points are awarded if the interpretation is not given or if it is wrong. The most common errors (which lead to considering the wrong interpretation, zero points) are, among the various possible: wrong structure formula; wrong m/z ratio; incorrect radical or neutral loss; erroneous or dubious assignment of the nature of radical-cation or cation; incorrect formation mechanism; misinterpretation or dubious interpretation of a homolytic or heterolitic cleavage. The definition of "doubt" also includes difficult reading due to unclear handwriting.

The points in Part B (multiple and open-ended answers) are awarded as follows:

Multiple answers: 2 points for the correct answer; zero points to the wrong or not given one;

Open answers: 12-15 points (sufficient: barely adequate knowledge of the subject, some serious errors); 16-17 points (good: more than satisfactory knowledge of the subject, some minor errors); 18-19 points (very good: practically exhaustive knowledge of the subject, some imperfections or defects in exposition); 20 points (excellent: impeccable, exhaustive knowledge of the subject, free of even minor errors, clear and technically impeccable exposition).

The student is rejected when one of the following occurs: (i) part A is insufficient; (ii) Part B is insufficient.

The evaluation in thirtieths can be interpreted as follows.

Points 18-23: sufficient knowledge of the subject, some serious errors;

Points 24-26: good knowledge of the subject, few minor errors;

Points 27-29: very good knowledge of the subject, some imperfections, some presentation defects;

30 points: excellent knowledge of the subject, impeccable, exhaustive and clear exposition, absent even the slightest imperfections; Honors are awarded when these qualities stand out as rare, far above the average of the hundreds of students examined.

Once the correction of the assignments has been completed, the exam grade is published on Almaesami and the papers, with any corrections, observations of the teacher and scores of the individual parts of the test, are made visible on EOL until the grade is recorded. Students are informed immediately with a notification from Almaesami and must immediately notify the teacher by e-mail if they intend to refuse the passing grade, an option that can be exercised only once. Normally, the vote is registered within three days.

For all matters not provided for in this chapter, the University teaching regulations apply.

Teaching tools

 

Blackboard, transparencies, PowerPoint presentations (and the like), tools that can be seen and/or used in the laboratory.

Teaching material published on virtuale.unibo.it.

Attention: the teaching material above is NOT intended to replace the textbooks nor sufficient (on its own) to pass the exam with profit.

The actual teaching material of the course are to be considered the recommended textbooks.

Office hours

See the website of Guido Galletti