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chem 122 > Instrumental Analysis > Flashcards

Instrumental Analysis Flashcards

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1
Q

any procedure that uses the interaction of EMR w/ matter to identify and/or to estimate an analyte

A

SPECTROSCOPY

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2
Q

molecules, ions, atoms, mixtures, solid, liquid, gas, solutions

A

MATTER

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3
Q

qualitative analysis

A

IDENTIFY

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4
Q

quantitative analysis

A

ESTIMATE

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5
Q

dual nature of light (both particles and waves)

A

EMR (Electromagnetic Radiation)

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6
Q

consists of perpendicular and oscillating electric and magnetic fields

A

LIGHT WAVES

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7
Q

distance from one wave peak to the next

A

WAVELENGTH

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8
Q

number of peaks that pass a given point per second

A

FREQUENCY

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9
Q

number of waves per cm

A

WAVENUMBER

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10
Q

what can the nature of light explain

A

REFLECTION, REFRACTION, AND DIFFRACTION

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11
Q

discrete packets of energy and particles of light or quanta of light

A

PHOTONS

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12
Q

E= hv

A

ENERGY

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13
Q

h

A

6.626 x 10^-34 J.s

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14
Q

The [ ] the energy, the [ ] the frequency and the wavenumber and the [ ] the wavelength

A

GREATER, HIGHER, SHORTER

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15
Q

what can the particle nature explain

A

ABSORPTION AND EMISSION OF LIGHT

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16
Q

a molecule that absorbs light photons will end up with?

A

INCREASED ENERGY

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17
Q

increased energy

A

MOLECULE IN EXCITED STATE

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18
Q

excited to ground state emitting the excess energy

A

FORM OF HEAT

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19
Q

rotation of compounds

A

MICROWAVE ENERGY

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20
Q

promote bond stretching

A

IR ENERGY

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21
Q

promotes electrons into higher orbitals

A

UV/Vis

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22
Q

ionizes molecules or even break bonds

A

SHORT-WAVELENGTH UV AND X-RAYS

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23
Q

what happens when a molecule absorbs UV-Vis radiations?

A

ELECTRONINC TRANSITIONS, ADDITIONAL VIBRATION AND ROTATION TRANSITIONS ALSO OCCUR

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24
Q

total energy absorbed

A

Eelec + Evib + Erot

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25
Q

a graph that shows how absorbance varies with wavelength

A

SPECTRUM

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26
Q

fraction of light that reaches a detector after passing through a sample

A

TRANSMITTANCE

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27
Q

formula of transmittance

A

T = I/Io

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28
Q

formula of absorbance

A

A= -log T

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29
Q

directly proportional to conc and path length of light

A

ABSORBANCE

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30
Q

heart of spectrophotometry; relation between absorbance and conc

A

BEER’S LAW / BEER-LAMBERT LAW

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31
Q

formula of Beer’s law

A

A= abc

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32
Q

unit for molar absorptivity

A

M^-1 cm^-1

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33
Q

characteristic for each substance at a particular wavelength

A

MOLAR ABSORPTIVITY

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34
Q

Transmittance decreases as conc increases

A
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35
Q

If all the light passes through a solution without any absorption, then absorbance is zero, and percent transmittance is 100%.

A
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36
Q

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

A

REAL DEVIATIONS

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37
Q

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.

A

CHEMICAL DEVIATIONS

38
Q

due to how the absorbance measurements are made

A

INSTRUMENT DEVIATION

39
Q

radiation outside the selected wavelength

A

STRAY/SCATTERED RADIATION

40
Q

analyte absorbs at the wavelength of the stray radiation

A

DUE TO PRESENCE OF STRAY RADIATION

41
Q

if the cells holding the analyte and the blank solutions are having different paths, or unequal optical characteristics

A

DUE TO MISMATCHED CELLS/CUVETTES

42
Q

occur when the sample absorbs some of the energy from the light

A

ABSORPTION

43
Q

when we hit a sample w/ some light and it emits light of a different wavelength

A

EMISSION

44
Q

an instrument for making relative measurements in the optical spectral region using light that is spectrally dispersed by the means of a dispersing element

A

SPECTROMETER

45
Q

spectroscopic techniques

A
  1. ATOMIC ABSORPTION SPECTROSCOPY (AA)
  2. INDUCTIVELY COUPLED PLASMA OPTICAL EMISSION SPECTROSCOPY (ICPOES)
  3. MOLECULAR SPECTROSCOPY
46
Q

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.

A

ATOMIC ABSORPTION SPECTROSCOPY (AA)

47
Q

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)

A

ELECTRODELESS DISCHARGE LAMP (EDL)

48
Q

used in LS AAS (LS-line source) for background correction purposes

A

DEUTERIUM LAMPS

49
Q

when a continuum sources radiation source is used for AAS, it is necessary to use a high resolution monochromator

A

CONTINUUM SOURCES

50
Q

conversion of the analyte to a reproductible amount of gaseous atoms that appropriately represent the sample

A

ATOMIZATION

51
Q

limits the accuracy, precision, and the limit of detection of the analytical instrument

A

SAMPLE ATOMIZATION

52
Q

introduce analyte in a steady manner (for AAS, flame)

A

CONTINUOUS ATOMIZERS

53
Q

introduce the analyte discontinuously (electrothermal atomizer)

A

DISCRETE ATOMIZERS

54
Q

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

A

MONOCHROMATOR

55
Q

generally uses an argon plasma to excite the atoms in the solution

A

INDUCTIVELY COUPLED PLASMA OPTICAL EMISSION SPECTROSCOPY (ICPOES)

56
Q

Advantages of ICP over AAS

A
  1. CAN MEASURE MORE ELEMENTS ALL AT ONCE; MEASURE A WHOLE RANGE OF SUBSTABCES AT ONCE
57
Q

UV-Vis spectroscopy covers the ultraviolet-vis range of the spectrum

A

MOLECULAR SPECTROSCOPY

58
Q

a particular type of infrared spectroscopy; uses an interferometer to produce an IR spectrum

A

FOURIER TRANSFORM INFRARED SPECTROSCOPY

59
Q

investigate tools used in many fields of science and engineering

A

INTERFEROMETER

60
Q

some molecules can take high-energy ultraviolet light, absorb it, and then emit it back out at lower-energy, longer wavelengths

A

FLUORESCENSE SPECTROSCOPY

61
Q

partner of IR spectroscopy; both technologies examine changes in vibration and rotation at the molecular level; measures the amount of light scattered

A

RAMAN SPECTROSCOPY

62
Q

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

A
63
Q

Po and P

A

Intensity or radiant power of EMR and Interaction with matter

64
Q

Transmittance increases, absorbance decreases

A
65
Q

Transmittance decreases, absorbance increases

A
66
Q

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.

A

DUE TO POLYCHROMATIC RADIATION

67
Q

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.

A

Path length dependence

68
Q

Increase in conc, increase absorbance

A

Conc dependence

69
Q

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

A

Wavelength dependence

70
Q

Concentration = Absorbance / Slope

A
71
Q

Relation between concentration and absorbance: Absorbance is directly proportional to the concentration of the substance. The higher the concentration, the higher its absorbance.

A
72
Q

a region of the electromagnetic
spectrum covering the range from just above the visible (7.8 𝑥 10−7) to approximately 10−4 m

A

Infrared (IR)

73
Q
  • Wavelengths within the IR region are usually given in
    micrometers (1μm = 10−6 m)
  • Frequencies are given in wavenumbers rather than in
    hertz
A

Infrared (IR)

74
Q

Wavenumber : 𝑣 (𝑐𝑚−1) = 1/ 𝜆(𝑐𝑚)

A
75
Q

spectroscopic method used for
identifying pure organic and inorganic compounds. With the
exception of some homonuclear molecules, all molecular
species absorb infrared radiation.

A

Infrared Spectroscopy

76
Q

Advantages of IR spectroscopy:

A
  1. Qualitative and quantitative analysis
  2. Sample preparation
  3. Sensitive and Time-saving technique
  4. It’s versatility
  5. Easy for interpretation
77
Q

Why does a molecule absorb some wavelengths of IR radiation?

A

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
Q

Why does a molecule absorb some wavelengths of IR radiation?

A

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.

79
Q

is an instrument that uses infrared radiation to
obtain a complete spectrum of the analyte for qualitative
identification.

A

FTIR

80
Q

identifies chemical bonds in a molecule by
producing an infrared absorption spectrum.

A

FTIR

81
Q

Advantages of FTIR

A
  • 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
Q

Parts of an Infrared Spectrum:

A
  1. Wavenumber
  2. Transmittance
  3. Peaks
  4. Functional Group Region
  5. Fingerprint Region
83
Q

tells us about the very particular energy of infrared light.

A

Wavenumber

84
Q

percentage of a [articular wavenumber that reaches the
detector

A

Transmittance

85
Q

means that IR light that corresponds to that
wavenumber is not being absorbed by the sample.

A

100% transmittance

86
Q

shows that the IR light of the particular wavenumber is not making
through to the detector and is being absorbed by the sample.

A

Peaks

87
Q

region where most of the information is used to
interpret the IR spectrum (4000 – 1500 𝑐𝑚−1)

A

Functional Group Region

88
Q

fingerprint of a known substance in a database. This region
important in finding an exact match of the sample. (1500 - 400 𝑐𝑚−1)

A

Fingerprint region

89
Q

two major instruments used to measure IR absorption:

A

1.Dispersive spectrometer

2.Fourier Transform Infrared Radiation (FTIR) spectrometer

90
Q

provided the robust instrumentation
required for the extensive application of
this technique.

A

Dispersive spectrometer

91
Q

Dispersive spectrometer components

A
  • Source of Radiation,
  • Monochromator, and
  • Detector
92
Q

as temp increases, intensity of every emitted wavelength increases

A

chem 122 (3 decks)

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