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Analytical Chemistry > Exam II > Flashcards

Exam II Flashcards

(54 cards)

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1
Q

Radio frequency

A

Spin flip in magnetic field
NMR-nuclear magnetic resonance
EPR/ESR- electron paramagnetic/spin resonance

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2
Q

Microwave

A 
Rotational energy (whole molecule)
Microwave spectroscopy-THZ spectroscopy
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3
Q

IR

A 
Vibrational energy levels (bonds) 
IR spectroscopy (dipole)
Raman spectroscopy (non dipole)
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4
Q

UV-vis

A

Electronic energy levels (valence)
UV-vis spectroscopy (absorbance)
Fluorescence (emission)

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5
Q

X-ray

A

Electron energy levels (core e-)

X-ray fluorescence

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6
Q

Gamma rays

A

Nuclear energy levels

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7
Q

Boltzmann distribution

A 
N1/n2=e^-(dE/KT)
dE-difference in energy levels
K- Boltzmann constant
T- temperature
N1/n2- ratio of amount at state 1 to 2
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8
Q

2 forms of spectroscopy

A

Absorbance/transmission

Emission

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9
Q

Beers law

A 
A=€bc
A- absorbance
€- molar absorbtivity
C- concentration
B- path length
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10
Q

Limits to beers law

A

Assume chromophores don’t interact
Assumes monochromatic light
No stray light

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11
Q

Absorbance instrumentation

A 
Source
Monochromator
Sample 
Detector
Readout device
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12
Q

Emission instrumentation

A 
Source
Excitation monochromator
Sample
90*
Emission monochromator
Detector
Readout device
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13
Q

Optical materials

A

Makes up lenses, mirrors, sample containers
IR: nacl, Kbr, csi, ge, znse
Vis: glass, plastic
UV: quartz, fused silica

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14
Q

Spectroscopy Sources

A 
Ir: thermal sources- nearnst glowers, nichrome wires, globar(heated wire gives off ir)
Vis: tungsten lamp
UV: deuterium lamp
Fluorescence: xenon arc lamp (UV-vis)
Lasers (emissions)
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15
Q

Continuum vs line source

A

Line- laser

Everything else is continuum

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16
Q

Monochromators

A 
Prism
- older
- less wavelength resolution
- resolution varies through spectrum
- spec 20
Grating
- newer, more expensive
-better resolution
- uniform resolution across spectrum
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17
Q

Spectroscopy Detectors

A

IR- thermal
-based on temp dependent electrical property
UV-vis- photon detectors
- amount of photons hitting detector

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18
Q

IR detectors

A

Thermocouples, bolometers, pneumatic cells (small gas filled chamber, measure expansion/contraction with dT)

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19
Q

UV-vis detectors

A

Photomultiplier tubes (photoelectric effect, older, bigger, good at low light, detect single photons)
Silicon based detectors (made from individual diodes, pn junction and DAD)
Pn junction ( little, relative e- to Si creates current)
DAD/diode array detector (measures entire spectrum simultaneously, less sensitive)
Charged coupled device/CCD (measure hv intensity)

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20
Q

Double beam instruments

A

Measure blank and sample simultaneously

Double beam in space vs. in time

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21
Q

Double beam in space

A

Monochromator sends light to reference and sample simultaneously, and to two detectors, and one read out

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22
Q

Double beam in time

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A

Monochromator sends light to chopper which allows light o switch between reference and sample, light passes to combiner to single detector and readout

23
Q

Chromophores

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A 
Conjugated substance
Widely applicable
Reasonably sensitive
Somewhat selective
Cheap and easy
24
Q

Fluorescence

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A 
Highly conjugated
Structurally rigid
Quantum yield (fraction of absorbed photons that are re-emitted)
F=kc 
Highly selective
Very high sensitivity
25
Column efficiency
``` N=L/H=16(tr/w)^2 N- number of theoretical plates (lg=more efficient) L- length of column H- plate height Tr- retention time W- column width ```
26
Chromatograph vs. chromatogram
Graph-apparatus | Gram- data
27
Gradient elation problems
Switch between optimal conditions Hv-temp variant Hplc- solvent comp
28
GC
``` Carrier gas tanks Oven (Sample injector Column Detector) Readout ```
29
GC Carrier gases
Helium, hydrogen, nitrogen
30
GC Sample injector
``` Split (part of sample) Split less (all of sample) ```
31
GC Columns
Packed (older, lg diameter, least efficient, larger sample sizes) Capillary (newer, sm diameter, most efficient, smaller sample sizes)
32
Ideal detector
``` Sensitive Stable and reproducible Linear range across orders of magnitude Operate 25-400*C Short response time Similar response to all analytes or highly predictable one to some Nondestructive Easy to use/reliable ```
33
GC detectors
FID- reduced carbons; oxidizes sample, releasing e- which create current; large linear range; medium high sensitivity TCH- older, simple; detects change in thermal conductivity; nondestructive; low sensitivity ECD- detect halogens, nitros,quinones, e- w/drawing; high sensitivity
34
HPLC
solvent res, pump, sample injector, column, detector, read out
35
HPLC Columns
normal phase- nonpolar solvent, polar column | reverse phase- polar solvent, nonpolar column
36
HPLC detectors
UV-vis: mid sensitivity, needs chromaphore fluorescence: high sensitivity, needs fluorophore refractive index: least sensitive, universal
37
GC vs HPLC
GC- limit by what can be in gas phase; HPLC- big and polar
38
Mass spectrometry
sample inlet, ion source, mass analyzer, detector, read out
39
sample inlet
probe that heats sample to gas phase
40
MS detector
charged plate
41
MS ion sources
ionize sample and determine sensitivity electron implact- hard ionization, many frags, beam of e- to knock off e- from sample chemical ionization- soft ionization, fewer frags, beam of ions that knock e- off sample
42
MS mass analyzer
magnetic sector- oldest, r=mV/Bze quadrupole- compact, fast, not super high mass resolution, limited mass range time of flight- large mass range, simple, limited resolution and sensitivity, slow, use time to detector to determine m/z ion trap- potential for higher mass res, FT mode, sample in cube of varying charged sides
43
tandem MS
identifies isomers | separate M+ by m/z, then fragments of M+
44
GC detectors
FID- reduced carbons; oxidizes sample, releasing e- which create current; large linear range; medium high sensitivity TCH- older, simple; detects change in thermal conductivity; nondestructive; low sensitivity ECD- detect halogens, nitros,quinones, e- w/drawing; high sensitivity
45
HPLC
solvent res, pump, sample injector, column, detector, read out
46
HPLC Columns
normal phase- nonpolar solvent, polar column | reverse phase- polar solvent, nonpolar column
47
HPLC detectors
UV-vis: mid sensitivity, needs chromaphore fluorescence: high sensitivity, needs fluorophore refractive index: least sensitive, universal
48
GC vs HPLC
GC- limit by what can be in gas phase; HPLC- big and polar
49
Mass spectrometry
sample inlet, ion source, mass analyzer, detector, read out
50
sample inlet
probe that heats sample to gas phase
51
MS detector
charged plate
52
MS ion sources
ionize sample and determine sensitivity electron implact- hard ionization, many frags, beam of e- to knock off e- from sample chemical ionization- soft ionization, fewer frags, beam of ions that knock e- off sample
53
MS mass analyzer
magnetic sector- oldest, r=mV/Bze quadrupole- compact, fast, not super high mass resolution, limited mass range time of flight- large mass range, simple, limited resolution and sensitivity, slow, use time to detector to determine m/z ion trap- potential for higher mass res, FT mode, sample in cube of varying charged sides
54
tandem MS
identifies isomers | separate M+ by m/z, then fragments of M+

Analytical Chemistry (2 decks)

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