SEM (Analytical techniques and Instrumentation, Pt 1) Flashcards
What made Spectrophotometry possible?
Monochromators
Visible light
a. <400 nm
b. 400 - 700 nm
c. > 700 nm
v
UV
a. <400 nm
b. 400 - 700 nm
c. > 700 nm
a
Infrared
a. <400 nm
b. 400 - 700 nm
c. > 700 nm
c
Color of infrared?
Red
Color of UV?
Violet
Relationship between wavelength and energy is Directly proportional
T or F
F
Inversely
The Wavelenth is long, the energy is low
this indicates?
a. Gamma
b. Radiowaves
Radiowaves (Infrared)
The Wavelenth is short, the energy is high
this indicates?
a. Gamma
b. Radiowaves
Gamma (Ultraviolet)
The concentration of a substance is directly proportional to the amount of light absorbed and is inversely proportional to the logarith of transmitted light
What is the law?
T or F
Beer-Lambert’s law
T
The formula for Beer’s law is:
A (Absorbance) = abc
What is “a”?
a. Molar absorptivity
b. Light path
c. concentration
a
The formula for Beer’s law is:
A (Absorbance) = abc
What is “c”?
a. Molar absorptivity
b. Light path
c. concentration
c
The formula for Beer’s law is:
A (Absorbance) = abc
What is “b”?
a. Molar absorptivity
b. Light path
c. concentration
b
Molar absorptivity and light path are constant
T or F
T
What is the standard value of light path?
1 cm
This correspond to the round cuvette
To compute the absorbance given the % transmittance:
a. A = 2- log %T
b. A = abc
c. A =2 + log %T
d. A = (Au x Cs) / As
a
What is the absorbance of Sodium in the cup with a transmittance of 45%?
0.3467
Solution:
A = 2 - log 45
= 0.3467
What is the percentage transmittance for Sodium if the absorbance is 0.69?
20%
Solution
%T = 10^(2-A)
&T = 10^(2-0.69)
= 20%
To determine the Cu (unknown analyte)
a. Cu = 2- log %T
b.Cu = abc
c. Cu = 2 + log %T
d. Cu = (Au x Cs) / As
d
Au = Absorbance of the unknown
Cs = Concentration standard
As = Absorbance standard
What is the Concentration of this Solution A if its absorbance is 0.420, comparing it to the concentration standard which is 69 with an absorbance standard of 0.911
31.81
Solution:
Cu = (Au x Cs) / As
Cu = (0.420 x 69) / 0.911
= 31.81
Blank is:
- distilled water
- Reagent
- Sample
that is used to subtract absorbance not due to analyte of interest
T or F
T
Blank sets the spectrophotometer to ___ absorbance
0
0 Absorbance = ______ transmittance
100%
Corrects the absorbance causd by the color of reagents
a. Reagent blank
b. Sample blank
a
Used to subtract the intrinsic absorbance caused by hemolysis, icterus, turbidity, or drug interference during sample analysis
a. Reagent blank
b. Sample blank
b
Use when the appearance of the sample is abnormal
a. Reagent blank
b. Sample blank
b
Used to zero the instrument before measuring test samples and other blanks
a. Reagent blank
b. Sample blank
a
Substance of known purity and concentration used to determine the concentration of the unknown analyte
a. Standard
b. Control
a
A solution containing various analytes with known target clues
a. Standard
b. Control
b
Analyzed samples to monitor analytical performance
a. Standard
b. Control
b
Contains 1 substance
a. Standard
b. Control
a
Various substances
a. Standard
b. Control
b
Has the same matrix of human substances (Such as serum)
a. Standard
b. Control
b
Requires definite concentration
a. Standard
b. Control
a
Ex:
100mg/dl (if more than or less than may affect the result)
Has target range of Value
a. Standard
b. Control
b
50 - 100 (Inbetween is normal)
Prevents stray light from entering the monochromator system
a. Light source
b. Entrance slit
c. Monochromator
d. Exit slit
e. cuvette
f. Photodetector
g. Read-out device
b
Provides polychromatic light which the sample will modify or attenuate by absorption
a. Light source
b. Entrance slit
c. Monochromator
d. Exit slit
e. cuvette
f. Photodetector
g. Read-out device
a
Emits Wavenlength:
UV
a. Deuterium/hydrogen
b. Xenon/Mercury
c. Tungsten
a
Emits Wavenlength:
UV to visible
a. Deuterium/hydrogen
b. Xenon/Mercury
c. Tungsten
b
Emits Wavenlength:
Most common; Visible - near Infrared
a. Deuterium/hydrogen
b. Xenon/Mercury
c. Tungsten
c
Controls the bandpass; only a narrow fraction passes through
a. Light source
b. Entrance slit
c. Monochromator
d. Exit slit
e. cuvette
f. Photodetector
g. Read-out device
d
Entrance slit prevents?
Stray light
Wavelength selector; isolates a portion of the spectrum emitted by the source and focuses it on the sample
a. Light source
b. Entrance slit
c. Monochromator
d. Exit slit
e. cuvette
f. Photodetector
g. Read-out device
c
Any light that does not come from the source is?
Stray light
In Monochromator:
Continous, linear; uniform separation of wavelengths
a. Prism
b. Diffraction grating
b
In Monochromator:
Continous, non-linear spectrum; better separation of high frequency light
a. Prism
b. Diffraction grating
a
In Monochromator:
Most common
a. Prism
b. Diffraction grating
b
Sample cell; may be round or square
a. Light source
b. Entrance slit
c. Monochromator
d. Exit slit
e. cuvette
f. Photodetector
g. Read-out device
e
Polychromatic is seen from light source up until monochromator
T or F
T
Monochromator converts polychromatic light to monochromatic light
T or F
T
What do you call the light that hits the sample cuvette?
a. Incident light
b. Light path
c. Transmitted light
Incident light
What do you call a light that travels through the cuvette?
a. Incident light
b. Light path
c. Transmitted light
b
What do you call the light came out from the sample cuvette that be detected in photodetector tube?
a. Incident light
b. Light path
c. Transmitted light
c
NOTE:
%T = (Incident light / Transmitted light) x 100
Can go through UV and IR
a. Quartz/fused silica
b. Plastic
c. Glass
a
Can go through UV and Vis
a. Quartz/fused silica
b. Plastic
c. Glass
b
Can go through Vis
a. Quartz/fused silica
b. Plastic
c. Glass
c
Which among the following is not appropriate for UV?
a. Quartz/fused silica
b. Plastic
c. Glass
c
Converts transmitted light energy into an equivalent amount of electrical energy
a. Light source
b. Entrance slit
c. Monochromator
d. Exit slit
e. cuvette
f. Photodetector
g. Read-out device
f
Photodetector converts light energy in to equivalent amount of _________ energy
Electrical
Processes the electrical signal, performs mathematical operations, displays the output
a. Light source
b. Entrance slit
c. Monochromator
d. Exit slit
e. cuvette
f. Photodetector
g. Read-out device
g
Read-out device consist of:
- Meter
- Display
T or F
T
Simplest photodetector Does not require voltage source
a. Barrier layer cell
b. Phototube
c. Photodiode
d. Photomultiplier tube
a
Requires external voltage source
a. Barrier layer cell
b. Phototube
c. Photodiode
d. Photomultiplier tube
b
Excellent linearity
a. Barrier layer cell
b. Phototube
c. Photodiode
d. Photomultiplier tube
c
Most sensitive because it can amplify the light signal 1000 fold Especially low level signal (Long wavelength: Radiowaves, etc.)
a. Barrier layer cell
b. Phototube
c. Photodiode
d. Photomultiplier tube
d
You can see absorbance in Read-out device
T or F
T
Quality assurance:
Wavelength accuracy is the wavelength set in the actual one selected by the monochromator checked using _______ glass or holmium oxide
a. Borosilicate
b. Quartz
c. Didymium
d. Flint
c
Quality assurance:
Absorbance check is done using glass filters and solutions that have known absorbance values
T or F
T
Quality assurance:
Linearity is a change in concentration results in a curve-line calibration curve (Beer’s law)
T or F
F
Straight - line
Linearity is determined using neutral density filters and dichromate solution
T or F
T
Any wavelength outside the band of interest
Stray light
Stray light causes absorbance error and loss of linearity; detected using?
a. Monochromator
b. Sharp cut off filters
c. Dull cut off filters
d. Photodetector
b
