MMSC 407 Exam 1 (A+ Guaranteed)
what is spectrophotometry? correct answers Measures the amount of specific colored light being
absorbed by or transmitted through a colored solution
measure light intensity as a function of wavelength
what is the order of the basic components of a spectrophotometer correct answers 1. light source
2. collimating lens
3. entrance slit
4. monochromator
5. exit slit
6. sample cuvette
7. PM tube
8. photodetector
9.display
Types of light sources correct answers Tungsten (quartz vapor): visible light
Hydrogen/deuterium: UV light
Xenon/mercury vapor: UV light
considerations for light source correct answers cool constant beam of light
intense light with small filament
easily replaceable, highly reproducible
what is a collimating lens? correct answers curved optical lens that make the light rays parallel
what is the purpose of a monochromator? correct answers selects a narrow range of wavelengths
from the white light
visible light wavelengths correct answers · 350-430 violet
· 430-475 blue
· 475-495 blue-green
· 495-505 green-blue
· 505-555 green
· 555-575 yellow green
· 575-600 yellow
· 600-650 orange
. 670-700 red
· Below 350 : UV
What is a bandpass? correct answers the actual range of wavelengths transmitted by a
monochromator.
each instrument will have a different bandpass
Bandpass are influenced by correct answers Type of monochromator
, Exit slit width
Distance between the monochromator and exit slit (greater the distance the more narrow the
bandpass)
Interference filter correct answers composed of 2 parallel sheets of half-silvered glass
surrounding a core of MgF2
ADV: good bandpass
DISADV: dirty easily, one filter per wavelength
prism correct answers ADV: narrow bandpass, spectrum of wavelengths
DISADV: expensive
diffraction grating correct answers Composed of polished reflective surfaces onto which sharply
defined, parallel grooves have been etched
ADV: narrow bandpass
DISADV: expensive
Properties of types of cuvettes correct answers shape: round or sqaure (square is better because it
relfects less light)
Type of material
clear glass
quartz: UV
plastic: most common
flow: through the cuvette
What is a photomutiplier tube? correct answers amplifies the primary signal
best and most senstive photodetector
wavelength calibration correct answers Preformed daily
Purpose: to ensure that the wavelength indicated on the wavelength dial is the actual wavelength
of the light passed by the monochromator
didymium filter
Absorbance calibration/photometric accuracy correct answers Preformed daily
Purpose: ensures the absorbance reading is accurate and linear
To ensure a lack of stray light
Neutral density filter (340 nm , 500 nm) and cobalt ammonium sulfate solutions
Temperature impact on spectrophotometry correct answers The amount of light emitted at each
wavelength depends upon the temperature of the filament
Temperature fluctuations can cause changes in the spectrum of light
Must allow spec to warm up before use
Manual colorimetric procedures correct answers What do we need to do to quantitate an analyte?
1. reagent blank: distilled water
what is spectrophotometry? correct answers Measures the amount of specific colored light being
absorbed by or transmitted through a colored solution
measure light intensity as a function of wavelength
what is the order of the basic components of a spectrophotometer correct answers 1. light source
2. collimating lens
3. entrance slit
4. monochromator
5. exit slit
6. sample cuvette
7. PM tube
8. photodetector
9.display
Types of light sources correct answers Tungsten (quartz vapor): visible light
Hydrogen/deuterium: UV light
Xenon/mercury vapor: UV light
considerations for light source correct answers cool constant beam of light
intense light with small filament
easily replaceable, highly reproducible
what is a collimating lens? correct answers curved optical lens that make the light rays parallel
what is the purpose of a monochromator? correct answers selects a narrow range of wavelengths
from the white light
visible light wavelengths correct answers · 350-430 violet
· 430-475 blue
· 475-495 blue-green
· 495-505 green-blue
· 505-555 green
· 555-575 yellow green
· 575-600 yellow
· 600-650 orange
. 670-700 red
· Below 350 : UV
What is a bandpass? correct answers the actual range of wavelengths transmitted by a
monochromator.
each instrument will have a different bandpass
Bandpass are influenced by correct answers Type of monochromator
, Exit slit width
Distance between the monochromator and exit slit (greater the distance the more narrow the
bandpass)
Interference filter correct answers composed of 2 parallel sheets of half-silvered glass
surrounding a core of MgF2
ADV: good bandpass
DISADV: dirty easily, one filter per wavelength
prism correct answers ADV: narrow bandpass, spectrum of wavelengths
DISADV: expensive
diffraction grating correct answers Composed of polished reflective surfaces onto which sharply
defined, parallel grooves have been etched
ADV: narrow bandpass
DISADV: expensive
Properties of types of cuvettes correct answers shape: round or sqaure (square is better because it
relfects less light)
Type of material
clear glass
quartz: UV
plastic: most common
flow: through the cuvette
What is a photomutiplier tube? correct answers amplifies the primary signal
best and most senstive photodetector
wavelength calibration correct answers Preformed daily
Purpose: to ensure that the wavelength indicated on the wavelength dial is the actual wavelength
of the light passed by the monochromator
didymium filter
Absorbance calibration/photometric accuracy correct answers Preformed daily
Purpose: ensures the absorbance reading is accurate and linear
To ensure a lack of stray light
Neutral density filter (340 nm , 500 nm) and cobalt ammonium sulfate solutions
Temperature impact on spectrophotometry correct answers The amount of light emitted at each
wavelength depends upon the temperature of the filament
Temperature fluctuations can cause changes in the spectrum of light
Must allow spec to warm up before use
Manual colorimetric procedures correct answers What do we need to do to quantitate an analyte?
1. reagent blank: distilled water
