mass spectra

Question 1

Typical peaks in the EI mass spectra of n-alkanes are 41, 55, 69. Molecular peak has typically a high intensity.

Answer 1

no: m/z = 29, 43, 57, 71; low intensity

Question 2

EI mass spectra of alkylated monocyclic aromatic hydrocarbons are characterized by the presence of a peak with m/z 91, which corresponds to the tropylium cation.

Answer 2

yes

Question 3

The molecular ion is always present in EI mass spectra.

Answer 3

no

Question 4

The EI mass spectra of polycyclic aromatic hydrocarbons (PAHs) are characterized by a doubly charged molecular ion (z=2), which has an m/z value two units lower than the singly charged molecular ion.

Answer 4

no, Doubly charged ions are rare in EI and, if present, their
m/z values would be approximately half those of singly charged ions, not “two units lower.”

Question 5

Cycloalkanes display similar EI mass spectra patterns as alkenes.

Answer 5

yes

Question 6

N-alkanes and i-alkanes have the same practically indistinguishable EI mass spectra.

Answer 6

no

Question 7

Polycyclic aromatic hydrocarbons (PAHs) usually give richly fragmented EI mass spectra. A molecular ion is usually of very low intensity.

Answer 7

true

Question 8

Mass spectra are used to determine the molecular weight of a compound.

Answer 8

yes

Question 9

The molecular formula of the characteristic fragments in the EI mass spectra of n-alkanes is CnH2n+1.

Answer 9

yes

Question 10

In mass spectra, the highest peak is referred to as the base peak. This peak always represents the molecular ion.

Answer 10

no

Question 11

Do Isotopes differ in the total number of neutrons?

Answer 11

yes

Question 12

Mass spectra are used to determine the structure of a compound

Answer 12

yes

Question 13

In MS, cold reservoir prevents evaporation before ionization

Answer 13

yes

Question 14

what is API?

Answer 14

atmospheric pressure ionization)

Question 15

Ionization of the analyte occurs either under vacuum or under atmospheric pressure

Answer 15

true

Question 16

Based on what ionization techniques are divided into2 groups: hard and soft?

Answer 16

based on the energy that is transferred to the analyte during the ionization process

Question 17

Is electron ionization considered to be hard ionization?

Answer 17

yes

Question 18

Is electron ionization the only example of hard ionization?

Answer 18

yes

Question 19

What info is given about a compound during hard ionization?
1) structure of the analyte
2) molecular weight
3) molecular weight distribution

Answer 19

1) structure

Question 20

What info is given about a compound while performing soft ionization?
1) structure
2) molecular weight

Answer 20

2) molecular weight

Question 21

EI works best with small, volatile, and thermally stable compounds.

Answer 21

true

Question 22

EI (electron ionization) is good technique for large molacules

Answer 22

false

Question 23

Chemical ionization (CI) is a soft ionization technique that is mainly used in GC-MS.

Answer 23

true

Question 24

the main difference between CI and EI is that chemical ionization uses the presence of a so-called reaction gas

Answer 24

yes

Question 25

The ion source for chemical ionization is structurally identical to the ion source for electron ionization. What is the source?

Answer 25

true, special component used to ionize the sample molecules using high-energy electrons.

Question 26

Is it true that in CI The analyte is subsequently ionized by proton transfer from the reaction gas.

Answer 26

yes

Question 27

EI AND CI take place under atmospheric pressure

Answer 27

false, they take place under deep vacuum

Question 28

API (Atmospheric pressure ionization) techniques are mainly used in GC-MS

Answer 28

no, they are used in LC-MS

Question 29

What MS technique is described here: sample is first dissolved in a suitable solvent and then converted into a spray (aerosol) form.

Answer 29

API (Atmospheric pressure ionization )

Question 30

Electrospray ionization is the most widespread ionization technique in LC-MS.

Answer 30

true

Question 31

Which is the softest of all ionization techniques in mass spectrometry?

Answer 31

Electrospray ionization

Question 32

Atmospheric pressure chemical ionization (APCI) is an extended ionization technique applicable in LC-MS

Answer 32

true

Question 33

Thermally unstable substances cannot be analyzed in APCI (Atmospheric pressure chemical ionization)

Answer 33

true

Question 34

ESI(Electrospray ionization) ionization is soft but harder than APCI.

Answer 34

false, APCI (Atmospheric pressure chemical ionization) ionization is soft but harder than ESI.

Question 35

Matrix assisted laser desorption ionization (MALDI) is a soft ionization technique applicable in LC-MS.

Answer 35

true

Question 36

MALDI is used mainly for biopolymers and synthetic polymers

Answer 36

true

Question 37

What are mass analyzers?

Answer 37

mass analyzers are critical components that separate ions based on their mass-to-charge ratio ( 𝑚 / 𝑧 m/z).

Question 38

Is it true that detectors transform energy of ions into an electric current?

Answer 38

yes

Question 39

Molecular ion has the lowest m/z ratio in the MS spectrum

Answer 39

False, it has the highest

Question 40

If forbidden losses are present in the MS spectrum, the observed ion is not a molecular ion.

Answer 40

True

Question 41

Both in n-alkanes and iso-alkanes: molecular ions is present, low intensity rich fragmentation .Is it true?

Answer 41

yes

Question 42

The most intensive peaks in n-alkanes are: m/z = 29, 43, 57, 71?

Answer 42

yes

Question 43

the mass spectra of alkenes and cycloalkanes with the same molecular weight are practically identical, therefore they cannot be distinguished?

Answer 43

yes

Question 44

For alkenes and cycloalkanes molecular ions is present, low intensity, poor fragmentation

Answer 44

kinda false: rich fragmentation

Question 45

the most intensive peaks :56, 69, 70 (cyclopentanes) a 55 (cyclohexanes).

Answer 45

true

Question 46

In monocyclic aromatic hydrocarbons molecular ion has high intensity and kinda poor fragmentation

Answer 46

true

Question 47

alkyl-substituted benzenes are characterised by a peak m/z=91?

Answer 47

true

Question 48

Polycyclic aromatic hydrocarbons (PAH) molecular peak has a high intensity, usually it is also the base peak (intensity 100 %). Thus, the fragmentation is very poor. Is it true?

Answer 48

yes

Question 49

Is it true that alcohols have mass spectra similar to alkenes?

Answer 49

yes

Question 50

How can we distinguish between alcohols and alkenes spectra?

Answer 50

alcohol can be distinguished based on the presence of the characteristic m/z 31 ion, which is not present in alkenes

Question 51

is it true that in mass spectra of alcohols The molecular ion is very intense?

Answer 51

no, The molecular ion is very weakly intense or not present at all.

Question 52

What is the difference between Selected ion monitoring (SIM) and Reconstructed ion chromatogram (RIC)?

Answer 52

Collects data for specific 𝑚/𝑧 m/z values during the analysis( selected) . Collects full scan data and extracts specific ions later (reconstructed)