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analytical chem315 > 4-6 > Flashcards

4-6 Flashcards

1
Q

_______ material has different composition from place to place in a material.

______ material has the same analyte cocnetration everywehre.

Chemical analysis is ______ unless we begin with a meaningful sample.

A representative sample must be take from a _______ material.

A

heterogenous
homogenous

meaningless
heterogenous

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2
Q

_____ is a process of selecting a representative bulk sample from the total material and make it a ______ laboratory sample through sample preparation. And lastly, divide into several ______ (homogenous)

A

sampling
homogeneous
aliquot

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3
Q

Field samples: measuring the concentration in the field
There should be ______ on the bottle and glass jar (date, time, GPS). And _____ equipment should be used (ex: acid washed polyethylene)

A

labelling

clean

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4
Q

Unless the _____ history of any sample is known with _____, the analyst is well advised not to spend time in analyzing it.

If the analyte concentration ______ between collection and analysis, the result would be _____.

A

complete; certainty

changes; meaningless

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5
Q 
The integrity of the sample and analyte \_\_\_\_\_ be maintained at all cost.
Thus \_\_\_\_\_ (mineral dusts) and \_\_\_\_\_  such as \_\_\_\_\_(avoid glass), and \_\_\_\_\_\_(soil: lid on container immediately after collection and avoid headspace), must be avoid.
A

contamination

analyte loss; adsorption; volatilization

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6
Q

To prevent microbal degradation can be prevent by using ____ _____ that has temperature of ______.
It can also be prevented by addition of ____ ______ but try not to degrade herbicide

A

ice chest
less than 10 degree
5% HNO3

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7
Q

Ball mill(glass): steel/ceramic balls rotated in drum to crush sample to fine powder

A

boron carbide ( tool used for griding)

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8
Q

Inorganic solid can be dissolved with ____ (with highest quality).

______acids dissolves metal through redox reaction.

A

acid

Non-oxidizing

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9
Q

If sample does not dissolve at mild conditions, ___ _____or ____ are the alternative method.
The organic material must be ____, and the inorganic elements must be in form _____ for analysis.

A

acid digestion; fusion; destroyed; suitable

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10
Q

Non-oxdizing acids such as ____, HBr, HF, dilute H2SO4, HNO3 and HCIO4 dissolves metals by redox reaction: M + nH+ to M^n+ + n/2H2

Must not use _____ when Sn (tin) is analyte.
____ dissolves silicates.
some anions form volatile species that will be lost from hot acids in open vessels: S2- to H2S, F- to HF, CO32- to CO2, and etc.
Volatile metal halides also can be lost (HgCl2 increases, SnCl4 increases)

A

HCl; HCl; HF

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11
Q

Substances that do not dissolve in acid will dissolve by _____ using hot, molten inorganic ___(solid flux such as Na2O2)
fine powder mix with huge mass( 20 times its mass) of solid flux and ___in Pt (at 300-1500), once cooled, place the crucible in beaker which contains 10 wt% highly pure____ to dissolve analyte then start analysis.

A

fusion; flux; melt; HNO3

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12
Q

Organic substances can be digested with ___ _____(ex: halogens in coal).
______ induced combustion 500mg coal in _____ vessel containing 6M NH4NO3(oxid), vessel ____with 20 bar of ___ and 1400W microwave power, ____released and dissolved in (NH4)2CO3 then use ion chromatgraphy for analysis.

A

dry ashing; Microwave; quartz; pressurized; O2; halides;

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13
Q

Organic substance can be digested with __ ____ as well.
Microwave digestion with an acid in ___ ____(high pressure).
Sample(250mg of oyster tissue) in 60mL telon vessel,
Add 1.5mL concentrated HNO3 and 1.5 mL concentrated H2SO4,
I min 700W microwave power then cool and transfer to volumetric flask, fill to the mark and analyze.

A

wet ashing;Telon bomb;

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14
Q

Other sample preparation techniques include:
_____sample
extracting analyte from ____ (close to 100%)
______ analyte to level be measured
_______ converting analyte to detectable form
removing/masking _____ species.

A

dissolving; matrix; concentrating; chemically; interfering

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15
Q

____ _____ technique (in the separation funnel)

is the process where, analyte is dissolved in solvent that does not dissolve whole sample and does not _____ analyte.

A

Liquid extraction ;decompose

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16
Q

Separation funnel is used for liquid extraction, but it has a problem: if forms ____.
It is used to ____ analyte, remove ____ and concentrate analyte.

A

emulsion; extract; matrix;

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17
Q

Example: ____ _____ ___ of pesticides from soil samples.
Soil + acetone and hexane placed in Teflon-lined bomb and heated to 150 (50 igher than boiling points of each solvent) and then cool and analyze (ex chromatography)

A

microwave-assisted extraction

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18
Q 
\_\_\_\_ \_\_\_ (ex: CO2 most common because it is cheapest)extraction:
increase pressure at certain temperature, causes phase change to liquid, temperature past \_\_\_ \_\_\_\_ to zone of supercritical fluid.
A

Supercritical fluid; critical point

No phase gap between liquid and gas

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19
Q

To reduce solvent consumption in liquid-liquid extraction:
___ supported L-L extraction analyze human plasma for prescription drugs : 200UL of diluted plasma (1:1 with 0.5M NH3) added to column with ____ ___ add 1.0 mL of immiscible organic solvent and wait for 5 min then evaporate solvent to dryness.
Then dissolve residue in mobile phase for LC.

Benefit is: dramatic _____ in solvent consumption and no _____ _____.

A

solid; diatomaceous earth; reduction; emulsion formation

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20
Q 
\_\_\_\_\_\_ \_\_\_\_\_\_techniques(solid phase extraction (SPE))
uses small volume of a chromatographic stationary phase to isolate analytes from a sample and remove much of sample matrix.
A

Solid extraction

steps are solvent increase in strength

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21
Q

_____ is the procedure in which analyte chemically modified to make easier to separate or detect quantity CH2O, other aldehydes and ketones in breath /cigarette smoke then trap them on tiny cartridge containing 0.35g of silica coated with 0.3 wt% 2,4 dinitrophenylhydrazine then elute with 5mL of acetonitrile and lastly using LC with UV detection to analysis.

A

derivatization

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22
Q

_____ is any technique that uses light to measure chemical concentration.

A

spectrophotometry

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23
Q

Properties of light are ____, ___.
It is perpendicular and oscillating electric and magnetic fields.

1 Hz(frequency) = 1 \_\_\_\_ /s
frequency(v) x wavelength = \_\_\_\_
E =plank's constant(h) x v = h x c /wavelength = h x c x v = h x c x (v with a line on it called \_\_\_\_)

Photons are light ____.
Longer wavelength = ____energetic

A

Plane, polarized
oscillation
speed of light(c); wavenumber= 1/wavelength

particles; less

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24
Q

visible light travels slower through matter than vacuum because the change in ___.

A

wavelength (frequency stays the same)

*refractive index is under speed of light

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25
Q

When light is absorbed by a sample the ____ (I or P)of the beam of light reduced.
It is the ___ per second per___ ___ of the light beam.
______(T) is the fraction of the original light that pass through sample. It has a range of 0-100%

A

irradiance (I or P)
energy; unit area

transmittance(T): T= P(for passed through sample)/Po(for incident)
*usually Po is bigger than P

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26
Q

______ is molecule + photon = higher energy -> promoted to excited state.

______ is molecule - photon = lower energy, and lowest energy state is ground state.

A

absorption; emission;

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27
Q

______ promote e- to higher energy orbitals.
______ break chemical bonds and ionize molecules.
______ stimulates rotation of molecules when absorbed.
______ stimulates vibrations (increases the amplitude of the vibrations of bonds)

(choose from visible and UV, X-ray ans short wavelength UV, microwave, infrared)

A

visible and UV
X-ray and shrot wavelength UV
microwave
infrard

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28
Q

______ is directly proportional to the concentration of light absorbing species in the sample.

A=log(Po/P) = _____ = E(it is the____) x c (concentration of molecule) x d(length of the sample vessel)
*the last equation is _____

No absorbance is when P___Po thus A=0
90%absorbance is when P =Po___ thus A=1, in this case, 10% is _____.

99% absorbance is A=2?*

A

absorbance(A) also called optical density.
-logT-> logT= -A and T = 10^-A
E (eplison)is the molar absorptivity (M-1 cm-1); beer’s law

equal(=)
/10(divide by 10); transmitted

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29
Q

if we measure how A ( or E) depending on wavelength then we create a _______ ____.

A

absorption spectrum

a graph showing how A or E(molar absorptivity) varies with wavelength.

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30
Q

_____ is the part of a molecule that absorbs light.
Any substance that absorb visible light appears ____ when white light is trasmitted through it.
It is because substance absorbs certain wavelengths of white light and our eyes detect wavelengths that are ______.

A

chromophore (ex: ferrozine3(Fe2 is the chromophore))
colored
not absorbed

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31
Q

Beer’s law only work with _____ ___ and in ___ solutions (_____M)

A

monochromatic radiation

dilute; less than 0.01M

32
Q

Beer’s law assumptions (3)

A

Absorbance is directly proportional to cocnentration of the absorbing species.

monochromatic radiation

good for dilute solutions (< or = to 0.01M) of most substance.

33
Q

Why Beer’s law do not apply for high concentration?

A

the proximity of molecules cause solute become solvent (change in properties for molecules)

presence of non-absorbing molecules interaction

And if absorbing molecule participates in concentration dependent equilibrium, eplison(E) alters with concentration.
ex: WA in high concentration HA may be not dissociated.

34
Q

Colors of visible light corresponding to the wavelength(nm).
remember shorter wavelength higher energy

380-420:____

420-440:\_\_\_\_
440-470:\_\_\_\_\_
470-500:\_\_\_\_\_
500-520:\_\_\_\_
550-580:\_\_\_\_
580-620:\_\_\_\_

620-780:____

A 
violet
violet-blue
blue
blue-green
green
yellow-green
yellow
orange
red
35
Q

The blank solution is used for compensates _____, ______, ____ by cuvet and solvent.

Sample is placed in cuvets.

A

reflection, scattering and absorption

36
Q

Gases are more ___ and need cells with longer path-length (___cm)

A

dilute; 10cm(cuvets are 1cms usually for liquid)

37
Q

measure IR(infrard) spectrum of unknown solid sample: mix __ sample with KBr and then apply ______transforms sample into a___ ___ and then measure absorbence of IR light as function of wavelength.

A

1% ; pressure (600 bar); translucent pellet

38
Q

Where should be measure absorbance and why?
position: _____.
Because ______ is greatest at _____ absorbance. The curve relatively ____ at that point.

Little variation in case of ______ ___,
most precise or reproducible when A is about _____. The ____ ____ should be adjust to fall in this range. High absorbance will cause too ___ light through sample and ____ is hard to measure.
Low absorbance will cause too ___ light through sample, and is hard to distinguish ____ of sample from that of reference.

A

the peak of the signal

sensitivity; maximum; flat

monochromator drift; 0.3 to 2; sample concentration

little; intensity;
much; transmittance

39
Q

For a compund to be quantified by spectrophotometry, the analyte must ___ ___and can be ____ from others.

A

absorb light; distinguishable

40
Q

most samples absorb light in _____ region (the ___ region is most relevant)

A

UV; visible

41
Q

In serum Fe determination, The Fe content of transferrin in blood serum is measured.
Procedure:
Fe is first ___ (form Fe2+) using ____ then the protein is _____ out with another ____, and centrifugation will leave Fe2+ in the ____ __.
To form colored complex, the _____ is added with ___ and ___ and create a purple complex.

A

reduced; acid(thioglycolic acid); precipitation; acid (trichloroacetic); acid solution;
supernatant; buffer; ferrozine

*maximum wavelength 562nm

42
Q

Glass is not suitable for UV radiation because it _____ it, and thus is only suitbale for visible

A

absorbes

*quartz are used for UV

43
Q

A ____ ___ should be measures first because it contain all reagents, but not analyte.
Any absorbance from blank is due to color of ____ ____ and color caused by __ ___ in used reagents.
The blank absorbance should be ____first from the absorbance of __ ____ before doing any calculations.

A suitable iron standards will be used to establish a ___ ____.

However the result would be ~10% too high because serum also contain Cu that forms a similar colored complex. It can be solved by ____ Cu.

A

reagent blank;
uncomplexed ferrozine; Fe impurities

subtracted; all samples
caliberation curve

masking

44
Q

Transferrin is a plasma Fe transport protein, and when it is without Fe it is called _____(apo-Tf).
The apo-Tf can be titrated with ____ to determine it’s concentration (using ____ ____ technique).

When Fe3+ binds to protein, red color develops and the absorption maximum is ____nm. The absorbance is equivalent to ________ bound to transferrin.

A

apotransferrin; Fe3+; spectrophotometric titrations(by UV-visible spectroscopy)

465nm; concentration of Fe3+

*In the example, Fe3+ nitrilotriacetate anion acetate solution is used.

45
Q

When molecule absorbs light that has sufficient energy to cause ____ ____ and cause ____ and ____ _____ , that is changes in the vibrational and rotational states occurs as well.

electronic absorption bands are usually _____ because many different vibrational and rotational ____ are available at slightly different _____.

A

electronic transition; vibrational; rotational transitions

broad; levels; energies

46
Q

vibrational transitions usually involve _____ rotational transitions. _____ _____ usually involve simultaneous vibrational and rotational transitions.

A

simultaneous; Electronic transitions

47
Q

Upon absorb one photon with just the right energy to cause the following simultaneous changes:

1) a transition from the S0 to the S1 ____ ____
2) a change in _____ ____ from the ground vibrational state of S0 to an excited vibrational state of S1
3) a transition from on rotational state of S0 to a ____ rotational state of S1

A

electronic state
vibrational energy
different

48
Q

absorption _____ a molecule from the ____ _____ ____ S0 to a _____ _____ _____of the excited electronic state S1.

A

promotes
ground electronic state
vibrationally and rotationally excited level

49
Q

The first process after absorption is _____ ____ to the lowest vibrational level of S1.
R1 is the _____ _____, where vibrational energy is transferred to other molecules (solvent for example) through ______, not by emission of a photon.
The net effect is to convert part of the energy of the absorbed photon into _____ spread throughout the entire medium.

A

vibrational relaxation
radiationless transition
collisions
heat

50
Q

S1 is the ____ ____ _____ and T1 is the _____ _____ ____.
R is the ____ ____
Absorption could terminate in any of the ____ ____ of S1, not just the one shown in diagram.

A

lowest excited singlet
triplet electronic state
vibrational relaxation
vibrational levels

51
Q

_____ _______ is a radiationless transition between states with the same spin quantum numbers. (eg: S1 to S0)

____ _____ is a radiationless transition between states with different spin quantum numbers. (eg: T1 to S0)

_______ emission of a photon during a transition between states with the same spin quantum numbers. (eg: S1 to S0)

_______ emission of a photon during a transition between states with different spin quantum numbers. (eg: T1 to S0)

A

interal conversion
intersystem crossing
fluorescence
Phosporescence

52
Q

At S1 level, there are several events can happen, molecule could enter a highly excited vibrational level of S0 having the ___ energy as S1 and it is called the ____ _____.
From this excited state, the molecule can relax back to the ground vibrational state and transfer its energy to neighboring molecules through _____. If the molecule follows the path of Absorbance to R1 to IC to R2 , the entire energy of the photon will have been converted into _____.

A

same; interal conversion(IC)
collisions;
heat

53
Q

Molecule at S1 can ___ ___ in to an excited vibrational level of T1. Then R3 occurs to the _____ vibrational level of T1. And the molecule might undergo a second intersystem crossing to S0, following by the R4 (it is the ___ ____ _____). Then energy of light is converted in to ___ . When all energy is transferred to heat it is called ______ and fluorescence and phosphorescence are examples of it, and is emission of light from an excited state of molecule.

A

intersystem crossing (ISC)
lowest
radiationless vibrational relaxation
heat; luminescence

54
Q

a molecule could relax from S1 or T1 to S0 by ______.
The radiational transition S1 to S0 is called _____. The radiational transition T1 to S0 is called ______.
The relative rates of internal conversion, intersystem crossing, fluorescence, and phosphorescence depend on _____, ______, and conditions such as _____ and ____.
These two process are relatively ____. Molecules generally ____ from the excited state by radiationless transitions.

A 
emitting a photon
fluorescence
phosphorescence
the molecule; the solvent; temperature and pressure
rare; decay
55
Q

The energy of phosphorescence is ___ than the energy of fluorescence, so phosphorescence comes at ____ wavelengths than fluorescence.

A

less; longer

56
Q 
\_\_\_\_ \_\_\_\_\_\_\_ (SBS) is inconvenient for it place reference blank and sample \_\_\_\_\_ in beam thus not practical for \_\_\_\_ measurement, also \_\_\_\_\_\_\_\_ can drift and cause inaccurate result.
The quotient Itr/Io is number between 0-1 and is \_\_\_\_\_.
A

single-beam spectrophotometer; alternatively; kinetic
Io + detector response
Transmittance(T)

57
Q

____ _______ is beneficial for light passes ______ through reference blank(Io) and sample (Itr).
Beam chopped several times/second and measure A which is _______ for drift

A

double-beam scanning spectrophotometer

alternately

58
Q

UV visible double beam spectrophotometer uses one lamp at a time. ______ ___ lamp is used for (200 to 400nm) and there is _____ ____ lamp(like in automobile), _____ is used to select narrow band of wavelengths to enter. Light detected by ____ ____ (detector) creates current proportional to light int I.

A

deuterium arc; quartz halogen

photomultiplier tube

59
Q 
For light source \_\_\_\_ lamp (filament near 3000K) is an excellent source of visible and near IR(infrard) radiation for \_\_\_\_nm. UV-spectroscoy requires a \_\_\_\_\_ \_\_\_ lamp and controlled electric discharge causes D2 to dissociate and molecular emission produces UV radiation \_\_\_\_\_\_nm.
If IR(infrard) radiation is needed, \_\_\_\_\_ \_\_\_\_ \_\_\_\_ electrically heated to 1500K for \_\_\_\_\_cm-1.
A

tungsten; 320-2500nm
deuterium arc; 110-400nm
silicon carbide ‘globar’; 4000-200 cm-1

60
Q

_____ (a short hand for light amplification by stimulated emission of radiation) provide monochromatic (____wavelength) with a brightness 10^13 times larger than the sun.
It is _____ where all waves in are in phase, and ______ _____where electricfield oscilates in one plante.

A

laser; single;

coherent; plane polarized

61
Q

Laser with a wavelength of 3Um might have a _____ (range of wavelength) of 3 * 10^-14 to 3 * 10^-8 Um (radiant power falls to half of maximum value)
angular divergence of a laser beam is 0.05 degree which illuminate _____ target (eg. application in laser ablation -ICP-MS)
microscopic crater ablated in to a mussel shell. (p495?479)

A

bandwidth

smaller

62
Q

to measure trace elements in a tooth, tiny portion of the tooth are vaporized (_____) by a laser pulse and swept into a plasma. The plasma ionizes some of the atoms, which pass into a mass spectrometer that separates ions by their ____ and measures their _____. The method is called _______.
The old tooth contain more lead and antimony than modern tooth, and a lot of rare earth minerals.

A

ablated; mass; quantity; Laser ablation-plasma ionization mass spectrometry

63
Q

photon with energy that spans two states can be absorbed to ______. same photon can stimulate excited molecule to emit a photon and it is called _____.
One photon stimulates emission of many others.
Second photon emitted with ____ polarization as incident photon.
Broadband radiation needs powerful lamp/electric discharge.
The necessary condition for lasing is ____ and ____

A

raise molecule to excited state
stimulated emission
same
lasing medium (population inversion n2>n1) and long half-life

64
Q

Monochromators disperses light into its component wavelengths(multiple) and ___ ____ band of wavelength.
Light bending in prism is _____.
Light bending by grating is _____.

A

selects narrow
refraction
diffraction

65
Q

_____ is a reflective or transmissive optical component with a series of closely spaced lines (eg. 9000/mm)

A

grating

66
Q

In czerny turner grating:
different wavelength diffracted at _____ angles.
polychromatic light from entrance slit collimated in to ____ rays.
They are then reflected by ____ _____ to orientate and directs only one narrow band of wavelength to exit slit.

A

different
parallel
reflection grating

*Fully constructive interference when difference in length of two paths (a-b) a multiple of the wavelength of light: n x wavelength = a-b (p451)

67
Q

When light reflected from grating, ___ ____ behaves like a source of radiation.
Adjacent light rays are ‘______’ where the reinforce each other and ‘_________’ when partically/completely cancel each other.

A

each grove

in phase; not in phase

68
Q

_______ is the measure of the ability to separate two closely spaced wavelength.

resolution of grating is(nN) : wavelength/change in wavelength = diffraction order x number of grooves

The ____ grooves in a grating the better the resolution between closely spaced wavelengths.

A

resolution

more

69
Q

If we need to resolve lines that are 0.05nm apart at wavelegnth of 500nm , the required resolution would be 10^4(equation is _____). for a 1st order resolution, there must be ___groves in grating.

A

500nm/0.05nm; 10^4

70
Q

choosing monochromator bandwidth by the wider the exit slit the _____ the wavelength band selected.
slit width is related to ______(bw) of radiation instead of saying slit is 0.3nm wide, we say bw is 1.0nm wide slit width and we _____ energy to detector and leads to high ______ and good _____ (if bw> than peak width) and the peak shape distroted because bw should be ___ as wide as peak.

A

wider
bandwidth; increased; signal to noise; precision
1/5

71
Q

detectors produce an ____ ____when struck by photons, detector response is a function of ____ light wavelength.

A

electric signal; incident

72
Q

The greater the _____ the greater the current/voltage produced by incident irradiance (w/m^2)

A

sensitivity;

73
Q

_______ ___ (PMT) takes extremely low light intensities translated in to measurable electrical signals.

All photodetectors produce some small response in the absence of light and leads to ___ _____. arise from spontaneous emission of electron from cathod of PMT tube: ____ _____ will lead to greater dark current.

A

photomultiplier tube

dark current; higher temeprature

74
Q

spectrophotometer with a PMT detector can scan through a spectrum only ____ _____ at a time.

A

one wavelength

75
Q

_____ ____(spectrophotometer) measures all wavelength (entire spectrum) of a compound in a fraction of a second and is useful as a detector for LC

A

photodiode array

how does it work? p332, p457

analytical chem315 (5 decks)

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