1. QUALITATIVE Chemical AnalysisBy
GC-MS

2. As in a running race, the group of components start together at the same point (the origin in chromatography).
As the race proceeds, the components (‘competitors’) tend to spread out. The longer the race, the more spread out the field will be (higher resolution).
There are two ways you could judge this race:
(1) give all competitors the same amount of time and see which ones travel further in the given time (like Retention factor, Rf) components -as in paper and thin layer chromatography.
(2) give all competitors the same distance to travel and see which ones complete the distance faster than others (like Retention time, Rt) - as in column chromatography, HPLC and GC.

3. Chromatographic determinations
Liquid chromatography
Non volatile, semi volatile and volatile
specially for non volatile
Gas Chromatography
Volatile and semi volatile
Nonvolatile if converted to volatile compounds after derivitization

4. Principles of Separation on a column

5. Principles of Separation

6. Principles of Separation

7. Principles of Separation

8. Principles of Separation

9. Principles of Separation

10. Principles of Separation

12. Heart of chromatography

13. FILM THICKNESS

15. GC Detectors Thermal Conductivity detectors (TCD) GC-TCD
Flame ionization detectors (FID) GC-FID
Electron capture detectors (ECD) GC-ECD
Nitrogen Phosphor detectors (NPD)
Fourier transfor infra red spectroscopy (FTIR) GC-FTIR .
Mass spectrometer (MS) GC-MS

16. Schematic representation of GC-MS

17. Evaluation of Mass Spectrum

19. Total ion chromatograms (TIC)

20. Ionizations Chemical Ionizations (CI) Electron impact ionization (EI)
Ions collusion breaks the compound
Electron impact ionization (EI)
Electron field (electron collusion breaks the compound)
Power and electron is important
70eV
Cold electron ionization

21. Mass analyzer Quadrupole Mass Analyzer Time of Flight Mass Analyzer
MW up to 1050
Time of Flight Mass Analyzer
Proteins and high molecular weight compound
Magnetic Sector Mass Analyzer
Electrostatic Sector Mass Analyzer
Quadrupole Ion Trap Mass Analyzers
Ion Cyclotron Resonance

22. GC-MS Analysis Quantitative Qualitative Selected ion monitoring
Full scan MS
Qualitative

23. requirements Column selection Temperature
Based on compound and column polarities.
Temperature
Isocratic
Temperature programming
Carrier gas flow rate and pressure,
sample volume injected
Injection method
Solution
split
splitless
split ratio
Gas
Head space
Head space SPME
Results evaluations

24. Sample extractions and preparation prior to GC analysis
Liquid-liquid extraction (LLE)
Solid phase extraction (SPE)
Solid phase micro extraction (SPME)
Single drop extraction (SDE)
Dispersive liquid-liquid microextraction (DLLME)
And so on

25. Factors to Consider in Identification
• Chromatographic tR and peak shape
• Adequate S/N ratio
• Presence of molecular ion
• Characterization of blanks and carry-over
• Comparison with reference standard
• MS fragmentation pattern

26. the same sample using same GC column and same analysis method
the same chromatogram
Qualitative analysis

27. Factors affecting retention time (tR)
Analysis conditions
Column (dimension & stationary phase)
Column pressure
Temperature
Degradation of column
Existence of active points such as contamination
carrier gas
Distance between injection and detection
all peaks appear at shorter times when you cut off part of column

28. Relative retention The advantageous some limitations
it depends only on the ratio of distribution coefficients, and the effects from some parameters, such as column length and carrier gas flow, are basically cancelled out.
some limitations
Measurement errors will increase for target peaks located far from reference peak and it is hard to find a relation with a chemical structure.

29. To solve problems in identification using tR
relative retention
and
retention index

30. Kovats retention index (RI or I)
a concept used in gas chromatography to convert retention times into system-independent constants. The index is named after the Hungarian-born Swiss chemist Ervin Kováts, who outlined this concept during the 1950s while performing research into the composition of the essential oils
The retention index of a certain chemical compound is its retention time normalised to the retention times of adjacently eluting n-alkanes. While retention times vary with the individual chromatographic system

31. Retention (Kovat’s) index
Isothermal Kovats retention indices
Ix = 100n + 100[log(tx) − log(tn)] / [log(tn+1) − log(tn)]
Non-isothermal Kovats retention indices (from temperature-programming, using definition of Van den Dool and Kratz)
Ix = 100n + 100(tx-tn) / (tn+1 − tn)

32. Where:
I : Kovats retention index, n: the number of carbon atoms in the smaller n-alkane, N: the number of carbon atoms in the larger n-alkane, the retention time.

33. Advantage of Retention index
the derived retention indices are quite independent of
column length,
film thickness,
diameter,
carrier gas velocity and pressure,
void time
allow comparing values measured by different analytical laboratories under varying conditions.
Tables of retention indices can help identify components by comparing experimentally found retention indices with known values

34. ResTek Company data base

35. Column coating and Kovat’s index

36. Analysis tools for identifications by GC-MS
Library search
De-convolution software
Literature search

37. Examples of MS Library 1. Data base for general compounds
NIST ( spectra, 2005Edition)
WILEY ( spectra; Ver 8)
2. Data base for special compounds
FFNSC library (Flavor and fragrance, with retention indice
Pflegar/Maurer/Weber Data base (drug and metabiolites,etc)
Pesticides Database; etc.
3. personal database
Most of them are for 70eV with Quadruple mass analyzer

38. Example

39. Library search results

40. RI

41. Search methods of Library
Forward search
Most peaks in an unknown spectrum are used for this search.
Reverse search
It verifies that the peaks in reference spectrum are presented in unknown spectrum
Index search
Reference spectra registered in a library are searched by compound name, CAS number, molecular weight, and so on.

42. Example of a Library search using retention index

46. Pherobase (http://www.pherobase.com)

47. pherobase

50. Out put results after all evaluations

51. Bottom Line
There are many complicated opinions of “good enough” criteria to meet MS-based identification standards But they are all based on
generalizations, not scientific assessments at all actual conditions
The bottom line is rates of false pos/neg If analytical conditions shown to meet <5% false results in extensive validation (multi-matrix, multi-level, blind), then it should be acceptable

52. Peak Purity

53. GC-MS deconvolution
deconvolution is critical since it reconstructs a pure mass spectrum for each component that the mass spectrometer observes. Based on the pure spectrum, the corresponding component can be eventually identified and quantified. Deconvolution is challenging due to the existence of co-elution.

54. Automatic mass spectrometry deconvolution and identification system(AMDIS)

55. Analysis Applications Environmental monitoring and cleanup
Criminal forensics
Law enforcement
Sports anti-doping analysis
Security
Chemical warfare agent detection
Chemical Engineering
Food, beverage and perfume analysis
Astrochemistry
Medicine
Pattern recognition or finger prints of compounds

57. Finger prints Volatile and semi volatile patterns
Non volatile (derivetization)

58. In depth evaluation is required to identify the component

59. Protein sequencing
Using mass finger print