AnaChem - Gas Chromatography & Mass Spectrometry

How can the fragmentation pattern help us identify the sample introduced in the instrument?

• The fragments don't break following specific rules, so they give no information

• The information doesn't come from the fragments patterns, but from the spectrum

• The fragments' pattern gives information about the amount of carbons in the sample

• The fragments' molecular masses are connected to the mass of the sample

What is the main function of the ionization source in a mass spectrometer?

• To cause desorption of molecules from the crystal and stabilize them

• To ionize the sample's molecules in liquid state

• To initialize adsorption on the sample's crystal using a laser

• To release the sample's molecules from the crystal and ionize them

In gas chromatography, based on the chromatogram, the first peak represents which of the following?

• We cannot determine the identity of the peak

• The sample that is small with a higher boiling point

• The solvent

• The mobile phase

• The sample that is smaller with a lower boiling point

The retention time in a chromatogram is used to determine the identity of the sample in a qualitative analysis.

• True

• False

As a consequence of a positive ionization process, molecules undergo a process of fragmentation and form ions, namely cations and radicals. Which species will be identified by the detector?

• Cations

• Anions

• Radicals

• Both A and B

• All of the above

What is the role of the mass analyzer?

• To separate the molecules based on the phases

• To separate molecules based on molecule weight

• To separate molecules based on atomic mass

• To separate molecules based on m/z ratio

In GC-MS, the area of the peak is directly proportional to the amount of the compound.

• True

• False

In a mass spectrum, how do we define the peak with the highest density?

• Molecular peak

• Standard peak

• Base peak

• Principal peak

Why is it important that the molecule used as a matrix absorbs at a similar wavelength as the laser?

• To protect the sample from direct irradiation and keep the overall change neutral

• To store the irradiation energy and solidify the crystal's structure

• To expose the sample on the surface of the crystals to direct irradiation

• To prevent direct irradiation of the sample and promote ionization

Which of the following is incorrect about the mass analyzer?

• Light fragments will be the fastest to reach the detector

• Fragments with a higher molecular mass will be heavier

• Higher molecular mass will therefore take a longer time to reach the detector

• The lower the charge of a fragments, the more it will be accelerated and get to the detector faster