CHAPTER V: ANALYTICAL METHODS & INSTRUMENTATION Flashcards
1
Q
Most determinations made in the clinical laboratory are based upon measurements of radiant energy:
A
Emitted
Transmitted
Absorbed
Reflected under controlled conditions
2
Q
Travels as electromagnetic wave
A
RADIANT ENERGY
3
Q
Shorter the wavelength, higher
A
electromagnetic energy
4
Q
Distance between two peaks as light travels in a wavelike pattern
A
WAVELENGTH
5
Q
WAVELENGTH UNITS
A
Armstrong (A) ; Millimicron (mu) ; Nanometer (nm)
6
Q
1 nm = 1 um = [?] A = [?] m
A
10
10^-9
7
Q
TYPES OF ELECTROMAGNETIC ENERGIES
A
Cosmic rays
Gamma rays and x-rays
Visible
Ultraviolet
Infrared
Radio, TV, Microwave
8
Q
Is a photon emitted spontaneously by a radioactive substance
A
Gamma rays
9
Q
similar to that of the x-ray but with higher frequency
A
Gamma rays
10
Q
electromagnetic radiation of extremely short wavelength that is generated by sudden changes in the velocity of the electric charge
A
X-rays
11
Q
Ultraviolet region
A
Below 340
12
Q
Not visible
A
Below 340
13
Q
Visible spectra
A
340 - 700
14
Q
Visible; used in spectrophotometers
A
340 - 700
15
Q
Provides the wavelength being used
A
White light source (deuterium)
16
Q
Not visible; toxicology studies and determinations
A
Above 700
17
Q
Perceived as heat instead of light
A
Above 700
18
Q
Infrared region
A
Above 700
19
Q
Chemical reaction produces colored substance whose concentration is proportional to the analyte
A
COLORIMETERY
20
Q
Factors considered in colorimetry
A
Quality of color
Intensity of color
21
Q
Kinds of colorimetry
A
Visual colorimetry
Photoelectric colorimetry
22
Q
Photoelectric colorimetry
A
Spectrophotometry
Filterphotometry
23
Q
- use prisms or gratings to disperse light into a continuous spectrum
A
Spectrophotometry
24
Q
- use filters to isolate a narrow wavelength range of the spectrum
A
Filter photometry
25
- amount of light taken up by a solution
Absorbance
26
Cannot be measured directly but measurement using the % transmittance
Absorbance
27
- ratio of the radiant energy transmitted to the radiant energy incident on the sample
Transmittance
28
The amount of light absorbed is dependent on:
The concentration of the absorbing substance.
The thickness or depth of a solution. The length of light path or the diameter of the cuvet.
29
The concentration the substance is directly proportional to the amount of the light absorbed or inversely proportional to the transmitted light.
BEER'S LAW
30
Absorbance is directly proportional to the length of light path.
BOUGUER'S OR LAMBERT'S LAW
31
Mathematical relationship between absorption of radiant energy and the concentration of a solution:
32
Light being absorbed and transmitted
RADIANT ENERGY
33
Frequency of a wave is inversely proportional to the
wavelength
34
RADIANT ENERGY in nm
290 to 750 nm
35
Originates beyond the earth's atmosphere
Cosmic rays
36
Being measured
Visible
37
With extremely high frequency
Radio, TV, Microwave
38
The darker the color, the higher the
concentration
39
Light passes through a [?]
monochromator
40
Isolates a region of the spectrum
Monochromator
41
Next passes through a
Cuvet
42
Radiant energy is absorbed through this glassware
Cuvet
43
Transmitted light reaches a [?], Which converts light electrical energy that can be registered on [?]
Detector
Readout device
44
Provides electromagnetic radiation as visible, infrared, or ultraviolet light
Light source
45
Sources of radiant energy
Visible and near-infrared ranges
Ultraviolet ranges
46
Visible and near-infrared ranges: 2
Tungsten iodide
Halogen quartz
47
Ultraviolet ranges: 3
Hydrogen vapor lamp
Deuterium lamp
Mercury lamp
48
Tungsten iodide in nm
340 - 700 nm
49
Less desirable; uneven emission spectrum
Mercury lamp
50
Not suited for routine application
Xenon lamp
51
Problems result from stray light
Xenon lamp
52
Any wavelength outside the band transmitted by the monochromator
Stray light
53
Reduces straylight and prevent scattered light from entering the monochromator system
Entrance slit
54
Produces light of specific wavelengths from a light source
Wavelength selector or monochromator
55
Types of monochromators
1. Prisms
2. Diffraction gratings
3. Transmission filters
4. Interference filters
56
Wedge shaped pieces of glass quartz or sodium chloride
Prisms
57
Disperses like to form a spectrum of colors by refraction
Prisms
58
Device with small parallel grooves or slit
Diffraction gratings
59
As a prism [refract white light] and as a slit [diffract it into several spectra]
Diffraction gratings
60
Colored glass or gelatin between two plates of glass
Transmission filters
61
Light outside the transmission band or absorbed by the colored material
Transmission filters
62
Semi-transparent silver films on both sides of a dielectric such as MgF
Interference filters
63
Internal components of a spectrophotometer
1. Light source
2. Entrance slit
3. Wavelength selector or monokrom a tour
4. Exit slit
5. Analytical cell or cuvette
6. Photodetector
7. Readout device or meter
64
Holds the solution in which the absorption is to be measured
Analytical cell or cuvette
65
Analytical cell or cuvette: internal dimension
1 cm
66
Measures light intensity by converting like signal into electrical signal
Photodetector
67
Uses photosensitive materials in their cathodes
Photodetector
68
photosensitive materials
Cadmium sulfide
Cadmium selenide [visible region]
69
Release electrons when they are exposed to light energy
Photodetector
70
Types of detectors
Barrier-layer cells
Photomultiplier tube
Phototube/photoemissive tube
Photoconductive/photoresistive tube
71
Generate their own electrical output directly from light energy
Barrier-layer cells
72
Negative electrode
Selenium coated with silver
73
Positive electrode
Iron base
74
Found in older colori,meter
Barrier-layer cells
75
An electron tube capable of significantly amplifying a current
Photomultiplier tube
76
Photomultiplier tube advantages
Rapid response time
Very sensitive
77
Photomultiplier tubes precautions:
All [?] Must be carefully shielded from the photomultiplier tube to prevent burnout
Straylight and daylight
78
When radiant energy strikes the cathode, the emitted electrons are attached to the adjacent dynode. Which electron then emits several other electrons. The electrons emitted from the dynode or subsequently attracted to the second dynode, where the same emission cycle is repeated
79
Electrons go directly to the anode
Phototube
80
Constructed to respond to ultraviolet radiation
Phototube
81
Phototube limitation
Small amount of a photocurrent generated
82
Electrical resistance decreases as the level of incident light is raised
Photoconductive
83
The electrical energy from a detector is displayed
Readout device
84
Types of read out device
Direct reading system
Null point system
Digital readout
Microprocessor
85
Double beam spectrophotometer
Double beam in space
Double beam in time
86
All components are duplicated except the light source
Double beam in space
87
The two beams pass at the same time through different components
Double beam in space
88
Compensate for changes in light intensity
Double beam in space
89
Compensate for changes in absorbance of the reagent blank as the wavelength is changed in scanning operation
Double beam in space
90
Use the same components as a single beam instrument
Double beam in time
91
Duplicate of cuvet compartments
Double beam in time
92
Rotating wheel without ternate silvered sections [inserted after the exit slit]
Light beam chopper chopper
93
Two beams pass through the same components but not at the same time
Double beam in time
94
As a single-beam instrument is adjusted to zero absorbance with the blank before and between sample readings, the double beam system makes this adjustment automatically
