INSTRUMENTAL ANALYSIS ACS
COMPREHENSIVE EXAM 2026 STUDY
GUIDE QUESTIONS AND ANSWERS TESTED
SOLUTIONS
●● Know all the differences and the advantages of Chemical ionization
and Electron Impact
Answer: Electron Ionization:
-ionization is direct result of impact of high-energy electrons with
analyte molecule
-can be used for organic and inorganic compounds
-causes significant fragmentation in analyte
-it is possible for fragments to collide which may produce new
fragments that do not represent the bond structure of the original
precursor molecule (decrease pressure of the system to avoid this; less
molecules available for collision, less collisions of fragments)
-hard ionization
Chemical Ionization:
-soft ionization
-ionization results from collision of analyte molecules with ions of a
reagent gas that is introduced to the ionization chamber
-reagent gas is ionized with Electron ionization
-reagent gas = methane, ammonia, isobutane
, -electrons in EI of reagent gas are much higher in energy than in typical
EI (70 eV vs. 200 V)
-negative ion ionization is common (unlike EI)- this is bc reagent gas
slows electrons down enough so they can be captured
-NCI (negative chem. ionization) is common for halogenated cmpds
●● Know the differences between all the mass analyzers including the
m/z that each one measures at
Answer:
●● Know FT-MS
Answer:
●● Know the advantages of flame and graphite furnace
Answer:
●● Keep an eye out for which instruments are used for trace analysis
Answer:
●● Know how to calculate the resolution of two peaks
Answer:
●● Potential instruments vs current instruments
COMPREHENSIVE EXAM 2026 STUDY
GUIDE QUESTIONS AND ANSWERS TESTED
SOLUTIONS
●● Know all the differences and the advantages of Chemical ionization
and Electron Impact
Answer: Electron Ionization:
-ionization is direct result of impact of high-energy electrons with
analyte molecule
-can be used for organic and inorganic compounds
-causes significant fragmentation in analyte
-it is possible for fragments to collide which may produce new
fragments that do not represent the bond structure of the original
precursor molecule (decrease pressure of the system to avoid this; less
molecules available for collision, less collisions of fragments)
-hard ionization
Chemical Ionization:
-soft ionization
-ionization results from collision of analyte molecules with ions of a
reagent gas that is introduced to the ionization chamber
-reagent gas is ionized with Electron ionization
-reagent gas = methane, ammonia, isobutane
, -electrons in EI of reagent gas are much higher in energy than in typical
EI (70 eV vs. 200 V)
-negative ion ionization is common (unlike EI)- this is bc reagent gas
slows electrons down enough so they can be captured
-NCI (negative chem. ionization) is common for halogenated cmpds
●● Know the differences between all the mass analyzers including the
m/z that each one measures at
Answer:
●● Know FT-MS
Answer:
●● Know the advantages of flame and graphite furnace
Answer:
●● Keep an eye out for which instruments are used for trace analysis
Answer:
●● Know how to calculate the resolution of two peaks
Answer:
●● Potential instruments vs current instruments
