4-6 Flashcards
_______ 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.
heterogenous
homogenous
meaningless
heterogenous
_____ 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)
sampling
homogeneous
aliquot
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)
labelling
clean
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 _____.
complete; certainty
changes; meaningless
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.
contamination
analyte loss; adsorption; volatilization
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
ice chest
less than 10 degree
5% HNO3
Ball mill(glass): steel/ceramic balls rotated in drum to crush sample to fine powder
boron carbide ( tool used for griding)
Inorganic solid can be dissolved with ____ (with highest quality).
______acids dissolves metal through redox reaction.
acid
Non-oxidizing
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.
acid digestion; fusion; destroyed; suitable
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)
HCl; HCl; HF
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.
fusion; flux; melt; HNO3
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.
dry ashing; Microwave; quartz; pressurized; O2; halides;
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.
wet ashing;Telon bomb;
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.
dissolving; matrix; concentrating; chemically; interfering
____ _____ technique (in the separation funnel)
is the process where, analyte is dissolved in solvent that does not dissolve whole sample and does not _____ analyte.
Liquid extraction ;decompose
Separation funnel is used for liquid extraction, but it has a problem: if forms ____.
It is used to ____ analyte, remove ____ and concentrate analyte.
emulsion; extract; matrix;
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)
microwave-assisted extraction
\_\_\_\_ \_\_\_ (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.
Supercritical fluid; critical point
No phase gap between liquid and gas
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 _____ _____.
solid; diatomaceous earth; reduction; emulsion formation
\_\_\_\_\_\_ \_\_\_\_\_\_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.
Solid extraction
steps are solvent increase in strength
_____ 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.
derivatization
_____ is any technique that uses light to measure chemical concentration.
spectrophotometry
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
Plane, polarized
oscillation
speed of light(c); wavenumber= 1/wavelength
particles; less
visible light travels slower through matter than vacuum because the change in ___.
wavelength (frequency stays the same)
*refractive index is under speed of light
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%
irradiance (I or P)
energy; unit area
transmittance(T): T= P(for passed through sample)/Po(for incident)
*usually Po is bigger than P
______ is molecule + photon = higher energy -> promoted to excited state.
______ is molecule - photon = lower energy, and lowest energy state is ground state.
absorption; emission;
______ 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)
visible and UV
X-ray and shrot wavelength UV
microwave
infrard
______ 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?*
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
if we measure how A ( or E) depending on wavelength then we create a _______ ____.
absorption spectrum
a graph showing how A or E(molar absorptivity) varies with wavelength.
_____ 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 ______.
chromophore (ex: ferrozine3(Fe2 is the chromophore))
colored
not absorbed
Beer’s law only work with _____ ___ and in ___ solutions (_____M)
monochromatic radiation
dilute; less than 0.01M
Beer’s law assumptions (3)
Absorbance is directly proportional to cocnentration of the absorbing species.
monochromatic radiation
good for dilute solutions (< or = to 0.01M) of most substance.
Why Beer’s law do not apply for high concentration?
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.
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:____
violet violet-blue blue blue-green green yellow-green yellow orange red
The blank solution is used for compensates _____, ______, ____ by cuvet and solvent.
Sample is placed in cuvets.
reflection, scattering and absorption
Gases are more ___ and need cells with longer path-length (___cm)
dilute; 10cm(cuvets are 1cms usually for liquid)
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.
1% ; pressure (600 bar); translucent pellet
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.
the peak of the signal
sensitivity; maximum; flat
monochromator drift; 0.3 to 2; sample concentration
little; intensity;
much; transmittance
For a compund to be quantified by spectrophotometry, the analyte must ___ ___and can be ____ from others.
absorb light; distinguishable
most samples absorb light in _____ region (the ___ region is most relevant)
UV; visible
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.
reduced; acid(thioglycolic acid); precipitation; acid (trichloroacetic); acid solution;
supernatant; buffer; ferrozine
*maximum wavelength 562nm
Glass is not suitable for UV radiation because it _____ it, and thus is only suitbale for visible
absorbes
*quartz are used for UV
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.
reagent blank;
uncomplexed ferrozine; Fe impurities
subtracted; all samples
caliberation curve
masking
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.
apotransferrin; Fe3+; spectrophotometric titrations(by UV-visible spectroscopy)
465nm; concentration of Fe3+
*In the example, Fe3+ nitrilotriacetate anion acetate solution is used.
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 _____.
electronic transition; vibrational; rotational transitions
broad; levels; energies
vibrational transitions usually involve _____ rotational transitions. _____ _____ usually involve simultaneous vibrational and rotational transitions.
simultaneous; Electronic transitions
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
electronic state
vibrational energy
different
absorption _____ a molecule from the ____ _____ ____ S0 to a _____ _____ _____of the excited electronic state S1.
promotes
ground electronic state
vibrationally and rotationally excited level
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.
vibrational relaxation
radiationless transition
collisions
heat
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.
lowest excited singlet
triplet electronic state
vibrational relaxation
vibrational levels
_____ _______ 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)
interal conversion
intersystem crossing
fluorescence
Phosporescence
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 _____.
same; interal conversion(IC)
collisions;
heat
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.
intersystem crossing (ISC)
lowest
radiationless vibrational relaxation
heat; luminescence
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.
emitting a photon fluorescence phosphorescence the molecule; the solvent; temperature and pressure rare; decay
The energy of phosphorescence is ___ than the energy of fluorescence, so phosphorescence comes at ____ wavelengths than fluorescence.
less; longer
\_\_\_\_ \_\_\_\_\_\_\_ (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 \_\_\_\_\_.
single-beam spectrophotometer; alternatively; kinetic
Io + detector response
Transmittance(T)
____ _______ is beneficial for light passes ______ through reference blank(Io) and sample (Itr).
Beam chopped several times/second and measure A which is _______ for drift
double-beam scanning spectrophotometer
alternately
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.
deuterium arc; quartz halogen
photomultiplier tube
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.
tungsten; 320-2500nm
deuterium arc; 110-400nm
silicon carbide ‘globar’; 4000-200 cm-1
_____ (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.
laser; single;
coherent; plane polarized
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)
bandwidth
smaller
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.
ablated; mass; quantity; Laser ablation-plasma ionization mass spectrometry
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 ____
raise molecule to excited state
stimulated emission
same
lasing medium (population inversion n2>n1) and long half-life
Monochromators disperses light into its component wavelengths(multiple) and ___ ____ band of wavelength.
Light bending in prism is _____.
Light bending by grating is _____.
selects narrow
refraction
diffraction
_____ is a reflective or transmissive optical component with a series of closely spaced lines (eg. 9000/mm)
grating
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.
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)
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.
each grove
in phase; not in phase
_______ 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.
resolution
more
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.
500nm/0.05nm; 10^4
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.
wider
bandwidth; increased; signal to noise; precision
1/5
detectors produce an ____ ____when struck by photons, detector response is a function of ____ light wavelength.
electric signal; incident
The greater the _____ the greater the current/voltage produced by incident irradiance (w/m^2)
sensitivity;
_______ ___ (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.
photomultiplier tube
dark current; higher temeprature
spectrophotometer with a PMT detector can scan through a spectrum only ____ _____ at a time.
one wavelength
_____ ____(spectrophotometer) measures all wavelength (entire spectrum) of a compound in a fraction of a second and is useful as a detector for LC
photodiode array
how does it work? p332, p457
