Instrument Analysis Final Exam questions with
verified answers
13CNMR Ans✓✓✓ Spin 1/2 nucleus: no net splitting, single sharp
peaks of each type of carbon; weak signals means low abundance;
larger shift range and number of distinguishable carbons
Accuracy Ans✓✓✓ Limited by the quality of the blank, presence of
particulates (scatter radiation), interferents reacting with analyte
AES vs. AAS Ans✓✓✓ simultaneous, multi-element, stable source/low
background, more effective ionization, fewer interference
(oxides/ionizations), good linear range, good precision (1-2%), low LOD
(ppm-ppt)
Ambient ionization Ans✓✓✓ dart ionization source, apply potential ~1-
5kV → glow discharge (plasma) → forms ions, electrons, exited state
neutrals
Amperometry Ans✓✓✓ Set voltage at il (or above), measure current to
calculate concentration (kills identification ability)
Anharmonicity Ans✓✓✓ Difference between vibrational E does not
equal constant; actual potential equals Morse potential
,Anionic stripping voltammetry Ans✓✓✓ 1) Preconcentrate metal on
electrode (~ 1-30 min)
2) Stop stirring
3) Scan to more positive potential
Applications of AES Ans✓✓✓ Qualitative: not useful due to broad
bands, no identification; quantitative: poor selectivity, do
chromatography, rapid analysis for kinetics/titrations/chromatography
Arc lamps Ans✓✓✓ Continuous UV/visible light sources; deuterium
(180-370 nm), Xe (250-600 nm), high pressure Hg (254-580 nm)
Array transducer Ans✓✓✓ Multiple electron multipliers, micro channel
plates, can stack to increase gain; microFaraday array (spatial info);
phosphorescent screen = electron impact into light
Atomic absorption spectroscopy Ans✓✓✓ Used for the determination
of specific elements in analytical samples; applications: agriculture,
food industry, environment, petrochemical; poor for quantitative
analysis
Atomic emission spectroscopy (AES) Ans✓✓✓ An analytical technique
that uses light emission to measure the concentration and identity of a
metal in a sample
,Atomizer (nebulizer) Ans✓✓✓ Breaks liquids into smaller droplets for
AA; want a high amount of ground state atoms and low amount of
everything else
Attenuated total reflectance (ATR-IR) Ans✓✓✓ Shine light at an angle,
total internal reflection, single/multiple bounce; no sample prep, easy
background
Auxochrome Ans✓✓✓ Auxillary group that can be added to a
chromophore to modify the ability of that chromophore to absorb
Average mass Ans✓✓✓ Calculated using all isotopes of each element
at natural abundance
Batch inlet Ans✓✓✓ Gas phase introduction, directly infused through
small orifice, good for volatile analytes
Bathochromic shift (red) Ans✓✓✓ λmax → red due to conjugation and
resonance or charges and radicals
Beer-Lambert law Ans✓✓✓ Law stating that intensity of color change
is directly proportional to the concentration of an analyte in a solution
, Boundary potential Ans✓✓✓ pH electrode: reference electrodes
connected to unknown solution through salt bridge, internal electrode
connected to solution with known H+ concentration
Broadening Ans✓✓✓ In AA, peaks broaden at higher temperatures
Bromine isotope peaks Ans✓✓✓ 50/50 abundance of 79 and 81; more
than one Br: 79/79, 79/81, 81/81 ratios 1:2:1
Calculate ratio from binomial expansion → (1x + 1y)(1x + 1y)
Calibration curve Ans✓✓✓ Compares a measurable property, such as
absorbance, of a solution of unknown concentration to a set of
standard samples of known concentration
Chemical interference Ans✓✓✓ Some salts are not ionizable, use a
releasing agent or protecting agent
Chemical ionization Ans✓✓✓ Ionize reagent gas with EI (high
concentration), ion-molecule reactions with reagent gas ions and
neutrals (charge transfer)
Soft ionization: minimal fragmentation, get parent mass
Pros: simpler mass spectrum
Cons: no fragmentation library
verified answers
13CNMR Ans✓✓✓ Spin 1/2 nucleus: no net splitting, single sharp
peaks of each type of carbon; weak signals means low abundance;
larger shift range and number of distinguishable carbons
Accuracy Ans✓✓✓ Limited by the quality of the blank, presence of
particulates (scatter radiation), interferents reacting with analyte
AES vs. AAS Ans✓✓✓ simultaneous, multi-element, stable source/low
background, more effective ionization, fewer interference
(oxides/ionizations), good linear range, good precision (1-2%), low LOD
(ppm-ppt)
Ambient ionization Ans✓✓✓ dart ionization source, apply potential ~1-
5kV → glow discharge (plasma) → forms ions, electrons, exited state
neutrals
Amperometry Ans✓✓✓ Set voltage at il (or above), measure current to
calculate concentration (kills identification ability)
Anharmonicity Ans✓✓✓ Difference between vibrational E does not
equal constant; actual potential equals Morse potential
,Anionic stripping voltammetry Ans✓✓✓ 1) Preconcentrate metal on
electrode (~ 1-30 min)
2) Stop stirring
3) Scan to more positive potential
Applications of AES Ans✓✓✓ Qualitative: not useful due to broad
bands, no identification; quantitative: poor selectivity, do
chromatography, rapid analysis for kinetics/titrations/chromatography
Arc lamps Ans✓✓✓ Continuous UV/visible light sources; deuterium
(180-370 nm), Xe (250-600 nm), high pressure Hg (254-580 nm)
Array transducer Ans✓✓✓ Multiple electron multipliers, micro channel
plates, can stack to increase gain; microFaraday array (spatial info);
phosphorescent screen = electron impact into light
Atomic absorption spectroscopy Ans✓✓✓ Used for the determination
of specific elements in analytical samples; applications: agriculture,
food industry, environment, petrochemical; poor for quantitative
analysis
Atomic emission spectroscopy (AES) Ans✓✓✓ An analytical technique
that uses light emission to measure the concentration and identity of a
metal in a sample
,Atomizer (nebulizer) Ans✓✓✓ Breaks liquids into smaller droplets for
AA; want a high amount of ground state atoms and low amount of
everything else
Attenuated total reflectance (ATR-IR) Ans✓✓✓ Shine light at an angle,
total internal reflection, single/multiple bounce; no sample prep, easy
background
Auxochrome Ans✓✓✓ Auxillary group that can be added to a
chromophore to modify the ability of that chromophore to absorb
Average mass Ans✓✓✓ Calculated using all isotopes of each element
at natural abundance
Batch inlet Ans✓✓✓ Gas phase introduction, directly infused through
small orifice, good for volatile analytes
Bathochromic shift (red) Ans✓✓✓ λmax → red due to conjugation and
resonance or charges and radicals
Beer-Lambert law Ans✓✓✓ Law stating that intensity of color change
is directly proportional to the concentration of an analyte in a solution
, Boundary potential Ans✓✓✓ pH electrode: reference electrodes
connected to unknown solution through salt bridge, internal electrode
connected to solution with known H+ concentration
Broadening Ans✓✓✓ In AA, peaks broaden at higher temperatures
Bromine isotope peaks Ans✓✓✓ 50/50 abundance of 79 and 81; more
than one Br: 79/79, 79/81, 81/81 ratios 1:2:1
Calculate ratio from binomial expansion → (1x + 1y)(1x + 1y)
Calibration curve Ans✓✓✓ Compares a measurable property, such as
absorbance, of a solution of unknown concentration to a set of
standard samples of known concentration
Chemical interference Ans✓✓✓ Some salts are not ionizable, use a
releasing agent or protecting agent
Chemical ionization Ans✓✓✓ Ionize reagent gas with EI (high
concentration), ion-molecule reactions with reagent gas ions and
neutrals (charge transfer)
Soft ionization: minimal fragmentation, get parent mass
Pros: simpler mass spectrum
Cons: no fragmentation library
