Instrumental Analysis Final ACS Exam Questions and Answers
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Course
Instrumental Analysis ACS
Institution
Instrumental Analysis ACS
Instrumental Analysis Final ACS Exam Questions and Answers
Instrumental Analysis Final ACS Exam Questions and Answers
Instrumental Analysis Final ACS Exam Questions and Answers
Know the different types of cuvettes (plastic and quartz) and when they are used - ANSWER--cuvettes are usually m...
Instrumental Analysis Final ACS Exam
Questions and Answers
Know the different types of cuvettes (plastic and quartz) and when they are used -
ANSWER--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
- 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 - ANSWER-
Calculations for Raman Stokes and anti-stokes lines, Raleigh scattering and Raman
scattering - ANSWER--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 - ANSWER-
Signal to noise calculations - ANSWER-
Beer's law theory and calculations - ANSWER-A = 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?) -
ANSWER-Hard:
-EI
-
Soft:
-electrospray
-MALDI
-chemical
Mass spec instruments, advantages for quadrupole, TOF, etc. - ANSWER-
Theory behind MALDI - ANSWER--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 - ANSWER-
Precision, sensitivity trade-offs with GFAA, flame, ICP? - ANSWER-
Stokes shift theory for fluorescence - ANSWER-
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