Clinical Chemistry- Instrumentation Flashcards
- Which formula correctly describes the relationship
between absorbance and %T ?
A. A = 2 – log %T
B. A = log 1/T
C. A = –log T
D. All of these options
D. All of these options
- A solution that has a transmittance of 1.0 %T
would have an absorbance of:
A. 1.0
B. 2.0
C. 1%
D. 99%
B. 2.0
- In absorption spectrophotometry:
A. Absorbance is directly proportional to
transmittance
B. Percent transmittance is directly proportional to
concentration
C. Percent transmittance is directly proportional to
the light path length
D. Absorbance is directly proportional to
concentration
D. Absorbance is directly proportional to
concentration
- Which wavelength would be absorbed strongly
by a red-colored solution?
A. 450 nm
B. 585 nm
C. 600 nm
D. 650 nm
A. 450 nm
- A green-colored solution would show highest
transmittance at:
A. 475 nm
B. 525 nm
C. 585 nm
D. 620 nm
B. 525 nm
- SITUATION: A technologist is performing an
enzyme assay at 340 nm using a visible-range
spectrophotometer. After setting the wavelength
and adjusting the readout to zero %T with the
light path blocked, a cuvette with deionized water
is inserted. With the light path fully open and the
100%T control at maximum, the instrument
readout will not rise above 90%T. What is the
most appropriate first course of action?
A. Replace the source lamp
B. Insert a wider cuvette into the light path
C. Measure the voltage across the lamp terminals
D. Replace the instrument fuse
A. Replace the source lamp
- Which type of monochromator produces the
purest monochromatic light in the UV range?
A. A diffraction grating and a fixed exit slit
B. A sharp cutoff filter and a variable exit slit
C. Interference filters and a variable exit slit
D. A prism and a variable exit slit
D. A prism and a variable exit slit
- Which monochromator specification is required
in order to measure the true absorbance of a
compound having a natural absorption
bandwidth of 30 nm?
A. 50-nm bandpass
B. 25-nm bandpass
C. 15-nm bandpass
D. 5-nm bandpass
D. 5-nm bandpass
- Which photodetector is most sensitive to low
levels of light?
A. Barrier layer cell
B. Photodiode
C. Diode array
D. Photomultiplier tube
D. Photomultiplier tube
- Which condition is a common cause of stray light?
A. Unstable source lamp voltage
B. Improper wavelength calibration
C. Dispersion from second-order spectra
D. Misaligned source lamp
C. Dispersion from second-order spectra
- A linearity study is performed on a visible
spectrophotometer at 650 nm and the following absorbance readings are obtained:
The study was repeated using freshly prepared
standards and reagents, but results were identical
to those shown. What is the most likely cause of
these results?
A. Wrong wavelength used
B. Insufficient chromophore concentration
C. Matrix interference
D. Stray light
D. Stray light
- Which type of filter is best for measuring stray
light?
A. Wratten
B. Didymium
C. Sharp cutoff
D. Neutral density
C. Sharp cutoff
- Which of the following materials is best suited
for verifying the wavelength calibration of a
spectrophotometer?
A. Neutral density filters
B. Potassium dichromate solutions traceable to the
National Bureau of Standards reference
C. Wratten filters
D. Holmium oxide glass
D. Holmium oxide glass
- Why do many optical systems in chemistry
analyzers utilize a reference light path?
A. To increase the sensitivity of the measurement
B. To minimize error caused by source lamp
fluctuation
C. To obviate the need for wavelength adjustment
D. To reduce stray light effects
B. To minimize error caused by source lamp
fluctuation
- Which component is required in a
spectrophotometer in order to produce a
spectral absorbance curve?
A. Multiple monochromators
B. A reference optical beam
C. Photodiode array
D. Laser light source
C. Photodiode array
- The half-band width of a monochromator is
defined by:
A. The range of wavelengths passed at
50% maximum transmittance
B. One-half the lowest wavelength of optical
purity
C. The wavelength of peak transmittance
D. One-half the wavelength of peak absorbance
A. The range of wavelengths passed at
50% maximum transmittance
- The reagent blank corrects for absorbance
caused by:
A. The color of reagents
B. Sample turbidity
C. Bilirubin and hemolysis
D. All of these options
A. The color of reagents
- A plasma sample is hemolyzed and turbid. What
is required to perform a sample blank in order
to correct the measurement for the intrinsic
absorbance of the sample when performing a
spectrophotometric assay?
A. Substitute deionized water for the sample
B. Dilute the sample 1:2 with a standard of
known concentration
C. Substitute saline for the reagent
D. Use a larger volume of the sample
C. Substitute saline for the reagent
- Which instrument requires a highly regulated
DC power supply?
A. A spectrophotometer with a barrier layer cell
B. A colorimeter with multilayer interference
filters
C. A spectrophotometer with a photomultiplier
tube
D. A densitometer with a photodiode detector
C. A spectrophotometer with a photomultiplier
tube
- Which statement regarding reflectometry is true?
A. The relation between reflectance density and
concentration is linear
B. Single-point calibration can be used to determine
concentration
C. 100% reflectance is set with an opaque film
called a white reference
D. The diode array is the photodetector of choice
C. 100% reflectance is set with an opaque film
called a white reference
- Bichromatic measurement of absorbance can
correct for interfering substances if:
A. The contribution of the interferent to absorbance
is the same at both wavelengths
B. Both wavelengths pass through the sample
simultaneously
C. The side band is a harmonic of the primary
wavelength
D. The chromogen has the same absorbance at both
wavelengths
A. The contribution of the interferent to absorbance
is the same at both wavelengths
- Which instrument requires a primary and
secondary monochromator?
A. Spectrophotometer
B. Atomic absorption spectrophotometer
C. Fluorometer
D. Nephelometer
C. Fluorometer
- Which of the following statements about
fluorometry is accurate?
A. Fluorometry is less sensitive than
spectrophotometry
B. Fluorometry is less specific than
spectrophotometry
C. Unsaturated cyclic molecules are often
fluorescent
D. Fluorescence is directly proportional to
temperature
C. Unsaturated cyclic molecules are often
fluorescent
- Which of the following components is not needed
in a chemiluminescent immunoassay analyzer?
A. Source lamp
B. Monochromator
C. Photodetector
D. Wash station
A. Source lamp
- Which substance is used to generate the light
signal in electrochemiluminescence?
A. Acridinium
B. Luminol
C. Dioxetane phosphate
D. Ruthenium
D. Ruthenium
- Light scattering when the wavelength is greater
than 10 times the particle diameter is described by:
A. Rayleigh’s law
B. The Beer–Lambert law
C. Mie’s law
D. The Rayleigh–Debye law
A. Rayleigh’s law
- Which statement regarding nephelometry is true?
A. Nephelometry is less sensitive than absorption
spectrophotometry
B. Nephelometry follows Beer’s law
C. The optical design is identical to a turbidimeter
except that a HeNe laser light source is used
D. The detector response is directly proportional to
concentration
D. The detector response is directly proportional to
concentration
- The purpose of the nebulizer in an atomic
absorption spectrophotometer that uses
a flame is to:
A. Convert ions to atoms
B. Cause ejection of an outer shell electron
C. Reduce evaporation of the sample
D. Burn off organic impurities
A. Convert ions to atoms
- A flameless atomic absorption spectrophotometer
dehydrates and atomizes a sample using:
A. A graphite capillary furnace
B. An electron gun
C. A thermoelectric semiconductor
D. A thermospray platform
A. A graphite capillary furnace
- When measuring lead in whole blood using atomic
absorption spectrophotometry, what reagent is
required to obtain the needed sensitivity and
precision?
A. Lanthanum
B. Lithium
C. Triton X-100
D. Chloride
C. Triton X-100
- Interference in atomic absorption
spectrophotometry caused by differences
in viscosity is called:
A. Absorption interference
B. Matrix effect
C. Ionization interference
D. Quenching
B. Matrix effect
- All of the following are required when
measuring magnesium by atomic absorption
spectrophotometry except:
A. A hollow cathode lamp with a magnesium
cathode
B. A chopper to prevent optical interference from
magnesium emission
C. A monochromator to isolate the magnesium
emission line at 285 nm
D. A 285-nm reference beam to correct for
background absorption
D. A 285-nm reference beam to correct for
background absorption