INSTRUMENTAL ANALYSIS FINAL
ACS EXAM QUESTIONS 100%
CORRECT
Know the different types of cuvettes (plastic and quartz) and when they are used -
ANSWERS-cuvettes are usually made of plastic, glass and quartz
-plastic and glass are cheaper than quartz
-for light sources >280 nm = plastic
-for light sources >320 nm = glass
-for light sources <320 nm = quartz
Know all the differences and the advantages of Chemical ionization and Electron Impact
- ANSWERSElectron 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 - ANSWERS
Know FT-MS - ANSWERS
Know the advantages of flame and graphite furnace - ANSWERS
Keep an eye out for which instruments are used for trace analysis - ANSWERS
, Know how to calculate the resolution of two peaks - ANSWERS
Potential instruments vs current instruments - ANSWERS
Grating monochromator, spectrometer focal length - ANSWERS
Know Raman detectors - ANSWERS
Calculations for Raman Stokes and anti-stokes lines, Raleigh scattering and Raman
scattering - ANSWERS-Rayleigh scattering -same frequency
E = hν
- Raman scattering -changes in frequency
- Stokes lines: E = hν - ΔE
- Anti-Stokes lines: E = hν +ΔE
Appropriate sources/materials used in various instrumentation - ANSWERS
Signal to noise calculations - ANSWERS
Beer's law theory and calculations - ANSWERSA = a·b·c
A =ε·b·c
Transmittance T = P/Po
• Percent Transmittance %T =(P/Po)x100%
• Absorbance A = -logT = -log(P/Po)
Mass spec hard vs. soft ionization sources (examples of each, how are they different?) -
ANSWERSHard:
-EI
-
Soft:
-electrospray
-MALDI
-chemical
Mass spec instruments, advantages for quadrupole, TOF, etc. - ANSWERS
Theory behind MALDI - ANSWERS-used for high-boiling materials
-usually produces monovalent ions
-dissolve target analyte in solution containing crystal forming cmpd; droplets of solution
are deposited on a metal plate and solvent is allowed to evaporate, leaving analyte
trapped in crystalline matrix
Atomic emission/ ICP theory, deviations to Beers law - ANSWERS
Precision, sensitivity trade-offs with GFAA, flame, ICP? - ANSWERS
ACS EXAM QUESTIONS 100%
CORRECT
Know the different types of cuvettes (plastic and quartz) and when they are used -
ANSWERS-cuvettes are usually made of plastic, glass and quartz
-plastic and glass are cheaper than quartz
-for light sources >280 nm = plastic
-for light sources >320 nm = glass
-for light sources <320 nm = quartz
Know all the differences and the advantages of Chemical ionization and Electron Impact
- ANSWERSElectron 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 - ANSWERS
Know FT-MS - ANSWERS
Know the advantages of flame and graphite furnace - ANSWERS
Keep an eye out for which instruments are used for trace analysis - ANSWERS
, Know how to calculate the resolution of two peaks - ANSWERS
Potential instruments vs current instruments - ANSWERS
Grating monochromator, spectrometer focal length - ANSWERS
Know Raman detectors - ANSWERS
Calculations for Raman Stokes and anti-stokes lines, Raleigh scattering and Raman
scattering - ANSWERS-Rayleigh scattering -same frequency
E = hν
- Raman scattering -changes in frequency
- Stokes lines: E = hν - ΔE
- Anti-Stokes lines: E = hν +ΔE
Appropriate sources/materials used in various instrumentation - ANSWERS
Signal to noise calculations - ANSWERS
Beer's law theory and calculations - ANSWERSA = a·b·c
A =ε·b·c
Transmittance T = P/Po
• Percent Transmittance %T =(P/Po)x100%
• Absorbance A = -logT = -log(P/Po)
Mass spec hard vs. soft ionization sources (examples of each, how are they different?) -
ANSWERSHard:
-EI
-
Soft:
-electrospray
-MALDI
-chemical
Mass spec instruments, advantages for quadrupole, TOF, etc. - ANSWERS
Theory behind MALDI - ANSWERS-used for high-boiling materials
-usually produces monovalent ions
-dissolve target analyte in solution containing crystal forming cmpd; droplets of solution
are deposited on a metal plate and solvent is allowed to evaporate, leaving analyte
trapped in crystalline matrix
Atomic emission/ ICP theory, deviations to Beers law - ANSWERS
Precision, sensitivity trade-offs with GFAA, flame, ICP? - ANSWERS
