Question

(12) Match the Match the ionization source with the typical use. electron impact a. soft ionization using auxiliary gas chemical ionization b. soft ionization used w/ large molecules & TOF electrospray ionization c. high fragmentation for identification MALDI d. soft ionization often used with HPLC Tens

Answer 1

OPTION C. Electron impact ionization uses highly energetic electrons to bombard the sample to produce ions. Owing to the high energy of the electrons bombarding the sample, the ions get fragmented extensively. The fragmentation facilitates identification of even structure of molecules below MW 600 as the ions undergo rearrangement apart from fragmenting.

OPTION A. Chemical ionization is a soft ionization method, that involves inducing fragmentation in analyte molecules. It uses a reagent that is ionized by electron ionization, which then react with the analyte molecules in the gas phase to ionize the analyte molecules.

OPTION D. Electrospray ionization involves applying a high voltage to a sample liquid which is aerosolized. It is classified as a soft ionization technique since the sample molecules do not undergo extensive fragmentation. So this is often coupled with HPLC to produce dominant molecular ions of the different molecules in the analyte mixture.

OPTION B. Matrix-Assisted Laser Desorption Ionization is a mass spectrometry technique that analyzes the mass of sample molecules by using a laser energy absorbing matrix to produce ions from large macromolecules with minimal fragmentation. Due to the technique inducing negligible fragmentation, it is primarily employed for samples containing macromolecules that are fragile and fragment extensively on conventional methods to the extent of being unidentifiable.