Sector instruments

m/z = 120 M M (%) M+1 (%) M+2 (%)

C₂H₄N₂O₄ 120,017107 100 3,15 0,84 C₂H₆N₃O₃ 120,040916 100 3,52 0,65 C₃H₁₂N₄O 120,101111 100 5,00 0,31 C₄H₁₂N₂O₂ 120,089878 100 5,36 0,52 C₆H₆N₃ 120,056172 100 7,72 0,26

C₉H₁₂ 120,093900 100 9,92 0,44

How much R is needed? R>30000

Requirement for small molecules: Accuracy < 10ppm (measured-calculated)/calculated*10⁶

What is the accuracy of the measurement if M=120.091375 measured?

Alternative of elemental analysis: characterises the

individual components, not the sample in whole (Pro/Con)

HRMS: R>10000

Analyzers

Sector instruments

A sector field mass analyzer uses a static electric and/or

magnetic field to affect the path and/or velocity of the charged particles in some way. As shown above, sector instruments bend the trajectories of the ions as they pass through the mass analyzer, according to their mass-to-charge ratios, deflecting the more charged and faster-moving, lighter ions more. The analyzer can be used to select a narrow range of m/z or to scan through a range of m/z to catalog the ions present.

Time-of-flight

The time-of-flight (TOF) analyzer uses an electric field to accelerate the ions through the same potential, and then measures the time they take to reach the detector. If the

particles all have the same charge, their kinetic energies will be identical, and their velocities will depend only on their masses.

Ions with a lower mass will reach the detector first.

Quadrupole mass filter

Quadrupole mass analyzers use oscillating electrical fields to selectively stabilize or destabilize the paths of ions passing through a radio frequency (RF) quadrupole field created between 4 parallel rods. Only the ions in a certain range of mass/charge ratio are passed through the system at any time, but changes to the potentials on the rods allow a wide range of m/z values to be swept rapidly, either continuously or in a

succession of discrete hops.

Orbitrap

Orbitrap instruments are similar to Fourier transform ion cyclotron resonance mass spectrometers. Ions are

electrostatically trapped in an orbit around a central, spindle shaped electrode. The electrode confines the ions so that they both orbit around the central electrode and oscillate back and forth along the central electrode's long axis. This oscillation generates an image current in the detector plates which is recorded by the instrument. The frequencies of these image currents depend on the mass-to-charge ratios of the ions. Mass spectra are obtained by Fourier transformation of the recorded image currents.

Orbitraps have a high mass accuracy, high sensitivity and a good dynamic range.

Ion traps

The quadrupole ion trap works on the same physical principles as the quadrupole mass analyzer, but the ions are trapped and sequentially ejected. Ions are trapped in a mainly quadrupole RF field, in a space defined by a ring electrode (usually

connected to the main RF potential) between two endcap electrodes (typically connected to DC or auxiliary AC

potentials). The sample is ionized either internally (e.g. with an electron or laser beam), or externally, in which case the ions are often introduced through an aperture in an endcap

electrode.

MS ⁿ is possible

500000-1000000

– Extremely sensitive

– Broad range (40- 100kDa) – reproducible

– Whatever phase

– Easy combination with chromatography – Quantitation is possible

MS characteristics

100 spectrometers, no universal instrument

GC-MS

For high volatile molecules

SWOT analysis

Strength

- high sensitivity (10^-15g) - fast (10 spektrum/s)

- efficient (simple sample preparation) - easily coupled with chromatography - quantitative and qualitative information

Weaknesses

- expensive (ca 100 000 Euro) - needs special knowhow

- interpretation is difficult

SWOT analysis

Opportunities

- verification (data base)

- macromolecules (proteomics) - broad field application

Threats

- not every compound is detectable

- sensitivity is heavily dependent on compound

- precaution is needed when used together with chromatography

Nitrogen rule

If M is even, then number of N is even (CHNOSF molecules).

Fragmentation rules

chain branching: possible positions for cleavage

stable molecules tends to leave (CH₂=CH₂, CHCH, CO, CO₂, HCl, H₂O, N₂, NO₂ etc)

formation of stable cations (allylic, formyl, acetyl, tropilium, etc)

General rules

Fragmentation is unique to every compound Depends heavily on instrument/settings

A structure can be verified or excluded based on the fragmentation pattern, but not elucidated (there are exceptions)

„The spectrum is in accordance with the suggested structure”.

https://chem.libretexts.org/Bookshelves/Analytical_Chemistry/Supplemental_Modules_(Analytical_Chemistry)/Instrument al_Analysis/Mass_Spectrometry/Mass_Spec/Mass_Spectrometry_-_Fragmentation_Patterns

(m/z = 44) (m/z = 72)

(m/z = 58)

H₃C N H

CH₂ +

+ H₃C N H₃C

CH₂

ónium-reakció McLafferty-

átrendeződés ónium-reakció

(m/z = 86) (m/z = 114)

+ H₃C N H₃C

H

-hasadás

-hasadás

CH₃ N

H₃C CH₃

CH₂ +N +

H

H₃C

H₃C CH₃

CH₃ N H₃C

CH₃ +

+

(m/z = 129) CH₃ N

H₃C CH₃

CH₃

ku69941_ra-61-1-f_d_qe920 09/23/19 14:15:24 Hazai L./ Pallag E.

RT:0.00 - 9.50

0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0 5.5 6.0 6.5 7.0 7.5 8.0 8.5 9.0 9.5

Time (min) 0

10 20 30 40 50 60 70 80 90 100

Relative Abundance

6.09 6.11 6.15

5.92 5.96 5.85

5.81 6.21

5.73 6.31

5.66 5.59 6.33 5.48

6.41

5.36 6.45

5.25

6.50 5.15

5.07 4.98 4.87 6.57

6.65

4.76 6.76 7.73 7.95 8.10 8.22 8.36 8.60 8.73 9.41

4.43 4.56 3.34 4.17

3.10 3.90

2.95 2.69 2.01 2.31 1.82

0.01 0.29 0.56 1.05 1.33 1.59

NL:

3.17E8 TIC MS ku69941_ra -61-1- f_d_qe920

ku69941_ra-61-1-f_d_qe920 #2214-2848 RT:5.22-6.38 AV:635 NL:2.06E7 T:FTMS + c EI Full ms [33.0000-600.0000]

40 60 80 100 120 140 160 180 200 220 240 260 280 300 320 340 360 380 400 420 440

m/z 0

10 20 30 40 50 60 70 80 90 100

Relative Abundance

349.07055 C20H13O6

14.5 RDBE -0.32713 ppm

310.04712 C17H10O6

13.0 RDBE -0.22318 ppm 296.17564

377.06544 C21H13O7

15.5 RDBE -0.37472 ppm 175.03897

C10H7O3

7.5 RDBE -0.03077 ppm

416.08900 C24H16O7

17.0 RDBE -0.12134 ppm 358.13160

254.05736 C15H10O4

11.0 RDBE 0.01477 ppm 226.06253

C14H10O3

10.0 RDBE 0.36945 ppm 121.02841

C7H5O2

5.5 RDBE 0.05268 ppm 91.05427

C7H7

4.5 RDBE 0.44831 ppm

39.02278 328.08470

http://chemistry.syr.edu/totah/che575/support/3a1/3-3.MS.pdf