Instrumental Analysis Flashcards
(92 cards)
1
Q
any procedure that uses the interaction of EMR w/ matter to identify and/or to estimate an analyte
A
SPECTROSCOPY
2
Q
molecules, ions, atoms, mixtures, solid, liquid, gas, solutions
A
MATTER
3
Q
qualitative analysis
A
IDENTIFY
4
Q
quantitative analysis
A
ESTIMATE
5
Q
dual nature of light (both particles and waves)
A
EMR (Electromagnetic Radiation)
6
Q
consists of perpendicular and oscillating electric and magnetic fields
A
LIGHT WAVES
7
Q
distance from one wave peak to the next
A
WAVELENGTH
8
Q
number of peaks that pass a given point per second
A
FREQUENCY
9
Q
number of waves per cm
A
WAVENUMBER
10
Q
what can the nature of light explain
A
REFLECTION, REFRACTION, AND DIFFRACTION
11
Q
discrete packets of energy and particles of light or quanta of light
A
PHOTONS
12
Q
E= hv
A
ENERGY
13
Q
h
A
6.626 x 10^-34 J.s
14
Q
The [ ] the energy, the [ ] the frequency and the wavenumber and the [ ] the wavelength
A
GREATER, HIGHER, SHORTER
15
Q
what can the particle nature explain
A
ABSORPTION AND EMISSION OF LIGHT
16
Q
a molecule that absorbs light photons will end up with?
A
INCREASED ENERGY
17
Q
increased energy
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MOLECULE IN EXCITED STATE
18
Q
excited to ground state emitting the excess energy
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FORM OF HEAT
19
Q
rotation of compounds
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MICROWAVE ENERGY
20
Q
promote bond stretching
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IR ENERGY
21
Q
promotes electrons into higher orbitals
A
UV/Vis
22
Q
ionizes molecules or even break bonds
A
SHORT-WAVELENGTH UV AND X-RAYS
23
Q
what happens when a molecule absorbs UV-Vis radiations?
A
ELECTRONINC TRANSITIONS, ADDITIONAL VIBRATION AND ROTATION TRANSITIONS ALSO OCCUR
24
Q
total energy absorbed
A
Eelec + Evib + Erot
25
a graph that shows how absorbance varies with wavelength
SPECTRUM
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fraction of light that reaches a detector after passing through a sample
TRANSMITTANCE
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formula of transmittance
T = I/Io
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formula of absorbance
A= -log T
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directly proportional to conc and path length of light
ABSORBANCE
30
heart of spectrophotometry; relation between absorbance and conc
BEER'S LAW / BEER-LAMBERT LAW
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formula of Beer's law
A= abc
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unit for molar absorptivity
M^-1 cm^-1
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characteristic for each substance at a particular wavelength
MOLAR ABSORPTIVITY
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Transmittance decreases as conc increases
35
If all the light passes through a solution without any absorption, then absorbance is zero, and percent transmittance is 100%.
36
due to the limitations of beer's law itself; when conc of analyte is high, analyte begins to behave differently due to interactions (h-bonding); creates a screen thereby shadowing them from the incident light
REAL DEVIATIONS
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due to chemical species of the sample which is being analyzed; chemical phenomenon involving the analyte molecules due to association, dissociation and interaction w/ the solvent to produce a product w/ different absorption characteristics.
CHEMICAL DEVIATIONS
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due to how the absorbance measurements are made
INSTRUMENT DEVIATION
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radiation outside the selected wavelength
STRAY/SCATTERED RADIATION
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analyte absorbs at the wavelength of the stray radiation
DUE TO PRESENCE OF STRAY RADIATION
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if the cells holding the analyte and the blank solutions are having different paths, or unequal optical characteristics
DUE TO MISMATCHED CELLS/CUVETTES
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occur when the sample absorbs some of the energy from the light
ABSORPTION
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when we hit a sample w/ some light and it emits light of a different wavelength
EMISSION
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an instrument for making relative measurements in the optical spectral region using light that is spectrally dispersed by the means of a dispersing element
SPECTROMETER
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spectroscopic techniques
1. ATOMIC ABSORPTION SPECTROSCOPY (AA)
2. INDUCTIVELY COUPLED PLASMA OPTICAL EMISSION SPECTROSCOPY (ICPOES)
3. MOLECULAR SPECTROSCOPY
46
an atom in the vapor will absorb light of certain frequencies as a unique characteristic of that specific atom; sequential technique; have to measure one element after the other by changing the lamp.
ATOMIC ABSORPTION SPECTROSCOPY (AA)
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contains a small quantity of the analyte as a metal or a salt in a quartz bulb together with an inert gas (argon gas @ low pressure)
ELECTRODELESS DISCHARGE LAMP (EDL)
48
used in LS AAS (LS-line source) for background correction purposes
DEUTERIUM LAMPS
49
when a continuum sources radiation source is used for AAS, it is necessary to use a high resolution monochromator
CONTINUUM SOURCES
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conversion of the analyte to a reproductible amount of gaseous atoms that appropriately represent the sample
ATOMIZATION
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limits the accuracy, precision, and the limit of detection of the analytical instrument
SAMPLE ATOMIZATION
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introduce analyte in a steady manner (for AAS, flame)
CONTINUOUS ATOMIZERS
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introduce the analyte discontinuously (electrothermal atomizer)
DISCRETE ATOMIZERS
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comprises a dispersive element, an entrance slit and mirrors to create a parallel beam similar to sunlight, and an exit slit and mirrors to xetract the monochromatic light
MONOCHROMATOR
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generally uses an argon plasma to excite the atoms in the solution
INDUCTIVELY COUPLED PLASMA OPTICAL EMISSION SPECTROSCOPY (ICPOES)
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Advantages of ICP over AAS
1. CAN MEASURE MORE ELEMENTS ALL AT ONCE; MEASURE A WHOLE RANGE OF SUBSTABCES AT ONCE
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UV-Vis spectroscopy covers the ultraviolet-vis range of the spectrum
MOLECULAR SPECTROSCOPY
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a particular type of infrared spectroscopy; uses an interferometer to produce an IR spectrum
FOURIER TRANSFORM INFRARED SPECTROSCOPY
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investigate tools used in many fields of science and engineering
INTERFEROMETER
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some molecules can take high-energy ultraviolet light, absorb it, and then emit it back out at lower-energy, longer wavelengths
FLUORESCENSE SPECTROSCOPY
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partner of IR spectroscopy; both technologies examine changes in vibration and rotation at the molecular level; measures the amount of light scattered
RAMAN SPECTROSCOPY
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a large numbers of photons of certain wavelengths are absorbed by a molecule. These individual wavelengths are too numerous and too close to each other and a spectrum of broad bands of absorbed wavelengths are obtained
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Po and P
Intensity or radiant power of EMR and Interaction with matter
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Transmittance increases, absorbance decreases
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Transmittance decreases, absorbance increases
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it is common to use a polychromatic source of radiation with continuous distribution of wavelengths along with a monochromators to create a monochromatic beam from this source.
DUE TO POLYCHROMATIC RADIATION
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The longer the path length, the more molecules there are in the path of the beam of radiation, therefore the absorbance goes up. Therefore, the path length is directly proportional to the concentration.
Path length dependence
68
Increase in conc, increase absorbance
Conc dependence
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The blue solution do absorb the red radiation; The red solution can not absorb
the red radiation but it can absorb radiation that is complimentary to red
Wavelength dependence
70
Concentration = Absorbance / Slope
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Relation between concentration and absorbance: Absorbance is directly proportional to the concentration of the substance. The higher the concentration, the higher its absorbance.
72
a region of the electromagnetic
spectrum covering the range from just above the visible (7.8 ðĨ 10â7) to approximately 10â4 m
Infrared (IR)
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* Wavelengths within the IR region are usually given in
micrometers (1Ξm = 10â6 m)
* Frequencies are given in wavenumbers rather than in
hertz
Infrared (IR)
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Wavenumber : ðĢ (ððâ1) = 1/ ð(ðð)
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spectroscopic method used for
identifying pure organic and inorganic compounds. With the
exception of some homonuclear molecules, all molecular
species absorb infrared radiation.
Infrared Spectroscopy
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Advantages of IR spectroscopy:
1. Qualitative and quantitative analysis
2. Sample preparation
3. Sensitive and Time-saving technique
4. It's versatility
5. Easy for interpretation
77
Why does a molecule absorb some wavelengths of IR radiation?
A pair of atoms joined by a covalent bond
can be thought of as being like balls on the
end of a vibrating spring. The bond can
vibrate with different amounts of energy at a
frequency that depends on the masses of the
atoms and the strength of the bond.
78
Why does a molecule absorb some wavelengths of IR radiation?
At room temperature, most bonds will vibrate
with the lowest possible amount of energy. But
if radiation of the right frequency is supplied,
the bond can absorb energy and vibrate with
greater amplitude.
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is an instrument that uses infrared radiation to
obtain a complete spectrum of the analyte for qualitative
identification.
FTIR
80
identifies chemical bonds in a molecule by
producing an infrared absorption spectrum.
FTIR
81
Advantages of FTIR
* High sensitivity, resolution and speed of data
acquisition
* All wavelengths are detected and measured
simultaneously using Michelson interferometer that can
be recorded as an interferogram and subsequently
decoded by Fourier transform which is a mathematical
operation that is conveniently carried out by the
computer.
* The measured spectrum is complete with different
display options (%T, A, zoom, peak, height, and peak
area)
82
Parts of an Infrared Spectrum:
1. Wavenumber
2. Transmittance
3. Peaks
4. Functional Group Region
5. Fingerprint Region
83
tells us about the very particular energy of infrared light.
Wavenumber
84
percentage of a [articular wavenumber that reaches the
detector
Transmittance
85
means that IR light that corresponds to that
wavenumber is not being absorbed by the sample.
100% transmittance
86
shows that the IR light of the particular wavenumber is not making
through to the detector and is being absorbed by the sample.
Peaks
87
region where most of the information is used to
interpret the IR spectrum (4000 â 1500 ððâ1)
Functional Group Region
88
fingerprint of a known substance in a database. This region
important in finding an exact match of the sample. (1500 - 400 ððâ1)
Fingerprint region
89
two major instruments used to measure IR absorption:
1.Dispersive spectrometer
2.Fourier Transform Infrared Radiation (FTIR) spectrometer
90
provided the robust instrumentation
required for the extensive application of
this technique.
Dispersive spectrometer
91
Dispersive spectrometer components
* Source of Radiation,
* Monochromator, and
* Detector
92
as temp increases, intensity of every emitted wavelength increases
