SEPARAZIONE E CARATTERIZZAZIONE DI COMPOSTI ORGANICI

Module CROMATOGRAFIA E SPETTROMETRIA DI MASSA DI COMPOSTI ORGANICI (Modulo 1)

- chomatographic methods for the separation and purification of organic compounds;

 - mass spectrometry (MS);

 - use of separation techniques (GC, LC) coupled with MS; 

- application of the MS to the structural determination of organic compounds. 

Graduated in Chemical Sciences - Curriculum Organic and bioorganic chemistry, with the teaching of CHROMATOGRAPHY AND MASS SPECTROMETRY OF ORGANIC COMPOUNDS expands and deepens the basic knowledge in the sector of characterizing fields, acquired with the first degree. Moreover, hi/she matures an advanced scientific preparation on the aspects of the chemical / biochemical methodologies of investigation, with particular focus on bioorganic compounds e compounds of biological interest.

The course includes 6 CFU of which 4 of lectures and 2 of classroom exercises. If the teaching is given in a mixed or remote way, the necessary changes with respect to what was previously stated may be introduced, in order to respect the program envisaged and reported in the Syllabus.

Knowledge of basic organic chemistry.

Theoretical principles of the chromatographic separation. Retention (retention time and volume). Capacity factor. Selectivity, resolution, peak simmetry. Efficiency and theoretical plate. Differential migration of the analytes and chromatographic band spreading: multiple paths (Eddy diffusion), longitudinal diffusion, mass transfer between mobile, stagnant mobile and stationary phase. Equation of Van Deemter. Band broadening not due to the column. 

Classification of the chromatographic techniques: 

- The adsorption liquid chromatography (liquid/solid, LS). Low pressure liquid chromatography on the column (LPC) and thin layer chromatography (TLC). Description of the atmospheric pressure chromatographic system.

- High pressure liquid chromatography on the column (HPLC). Characteristics of the stationary phases used in normal-phase HPLC (liquid/solid) and reversed-phase HPLC (RP-HPLC, liquid/liquid). Description of the high pressure chromatographic system. The sample valve injector (“loop”). The pumps: syringe pump, single piston and double piston reciprocating pump. Pulse dampers. Mobile phases for HPLC: physical properties, eluting power and selectivity. Preparation of the mobile phase: dehydration, filtration and degassing. Sample preparation. Stationary and mobile phases. Examples of organic compounds separation by nornal- and reversed-phase HPLC. Optimization of the chromatographic conditions. Detectors for liquid chromatography: general properties (limit of detection, LOD, and linear dynamic range, LDR). Detectors: UV-Vis, diode array, refractive index, fluorescence. Mass spectrometer. 

- Size-exclusion chromatography. Principle; stationary and mobile phases. Examples of biopolymers separation.

- Ion-exchange chromatography. Principle; stationary and mobile phases. Examples of organic compounds separation: the amino acid analyzer. Post-column derivatization of amino acids by ninhydrin. 

- Affinity chromatography. Principle; stationary and mobile phases. Dye-protein affinity chromatography for protein purification. 

- Gas chromatography. Description of a gas chromatograph system. Adsorption gas chromatography (gas solid, GSC) and partition gas chromatography (gas liquid, GLC). Capillary and packed columns. The carrier gas. Solid and liquid stationary phases. Choosing the stationary phase. Detectors for gas chromatography: thermal conductivity (TCD), flame ionisation (FID), alkaline flame, electron capture (ECD). Mass spectrometer.

MASS SPECTROMETRY

Principles of the method. The Electron Ionization ion source. Operating principles. Construction and operation.

Magnetic sector analyzer. Resolution. Double-focusing (magnetic- electrostatic) analyzer. High resolution mass spectrometry. Nominal mass, exact mass, monoisotopic mass, relative molecular mass. Exact mass and the determination of molecular formula. 

Molecular ion and isotopic peaks. Criteria for the recognition of the molecular ion peak. Information deducible from the molecular ion and isotopic pattern. Nitrogen rule. 

Principles of fragmentation reactions of organic ions and interpretation of EI mass spectra. Quasi- equilibrium theory. Classification of the fragmentation reactions. Cleavage of sigma-bonds and rearrangements. Even-electron rule. Charge localization. Criteria for fragment ions intensity evaluation. 

Sigma-bond cleavage in small non-functionalized molecules. Fragmentation of compounds containing double bonds or heteroatoms. Alpha-cleavage (radical site initiated process) . Inductive cleavage (Charge-site initiated process). Fragmentation of cyclic compounds. Rearrangements. Typical fragmentation of the most common classes of organic compounds.

The Matrix assisted laser desorption/ionization (MALDI) source. Operating principles. MALDI matrices. Sample preparation. Calibration in MALDI.

Time-of-Flight (TOF) analyzer. Basic principles. Improving resolving power: delayed extraction and ion reflector. 

The Electrospray (ESI) source. Operating principles. Ions formation and ions transfer in ESI. 

The Atmospheric Pressure Chemical Ionization (APCI). Operating principles. 

Linear quadrupole analyzer. Operating principles.

Ion traps analyzer. Operating principles. 

Tandem mass spectrometry. Tandem-in-space and tandem-in-time.

Coupling gas-chromatography/MS (GC/MS) and Reversed Phase-High Performance Liquid chromatography/MS (HP-HPLC/MS).

2. J. H. Gross, MASS SPECTROMETRY- A Textbook, Springer 2011.

3. J. H. Gross, SPETTROMETRIA DI MASSA, EdiSES, 2016.

4. F.W. McLafferty, INTERPRETATION OF MASS SPECTRA University Science Books 1980.

5. K.A. Rubinson, J.F. Rubinson, Chimica analitica strumentale, 1a ed.,Bologna, Zanichelli, luglio 2002. ISBN 88- 08-08959-2.

The exam consists of an oral test carried out through an interview between the student and the examining commission aimed at ascertaining the degree of learning and understanding of the topics contained in the course program. In particular, the relevance of the answers to the questions asked, the quality of the contents, the ability to connect with other topics covered by the program, the ability to report examples, the technical language properties and the overall expressive ability of the student will be assessed.

Verification of learning can also be carried out on line, should the conditions require it.

The exam questions focus on all the topics covered in the lessons. Examples of questions are: ESI source; magnetic and electrostatic sector analyzers; mass spectrometry resolution; molecular ion and isotopic peaks; fragmentation of organic compounds; MALDI source; time-of-flight analyzers; quadrupole and ion trap analyzers; tandem mass spectrometry; Van Deemter equation; resolution and selectivity; efficiency of chromatographic columns; high performance liquid chromatography; HPLC detectors; gas chromatography; columns in gas chromatography; gas chromatography detectors; molecular exclusion chromatography; ion exchange chromatography; affinity chromatography. HPLC / MS and GC / MS interfacing.