Clinical Chemistry- Instrumentation Flashcards by H. JG

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

How well did you know this?

Not at all

Perfectly

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

How well did you know this?

Not at all

Perfectly

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

How well did you know this?

Not at all

Perfectly

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

How well did you know this?

Not at all

Perfectly

A green-colored solution would show highest
transmittance at:
A. 475 nm
B. 525 nm
C. 585 nm
D. 620 nm

B. 525 nm

How well did you know this?

Not at all

Perfectly

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

How well did you know this?

Not at all

Perfectly

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

How well did you know this?

Not at all

Perfectly

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

How well did you know this?

Not at all

Perfectly

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

How well did you know this?

Not at all

Perfectly

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

How well did you know this?

Not at all

Perfectly

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

How well did you know this?

Not at all

Perfectly

Which type of filter is best for measuring stray
light?
A. Wratten
B. Didymium
C. Sharp cutoff
D. Neutral density

C. Sharp cutoff

How well did you know this?

Not at all

Perfectly

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

How well did you know this?

Not at all

Perfectly

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

How well did you know this?

Not at all

Perfectly

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

How well did you know this?

Not at all

Perfectly

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

How well did you know this?

Not at all

Perfectly

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

How well did you know this?

Not at all

Perfectly

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

How well did you know this?

Not at all

Perfectly

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

How well did you know this?

Not at all

Perfectly

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

How well did you know this?

Not at all

Perfectly

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

How well did you know this?

Not at all

Perfectly

Which instrument requires a primary and
secondary monochromator?
A. Spectrophotometer
B. Atomic absorption spectrophotometer
C. Fluorometer
D. Nephelometer

C. Fluorometer

How well did you know this?

Not at all

Perfectly

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

How well did you know this?

Not at all

Perfectly

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

How well did you know this?

Not at all

Perfectly

25. Which substance is used to generate the light signal in electrochemiluminescence? A. Acridinium B. Luminol C. Dioxetane phosphate D. Ruthenium

D. Ruthenium

26. 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

27. 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

28. 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

29. 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

30. 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

31. 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

32. 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

33. When measuring calcium by atomic absorption spectrophotometry, which is required? A. An organic extraction reagent to deconjugate calcium from protein B. An internal standard C. A magnesium chelator D. Lanthanum oxide to chelate phosphates

D. Lanthanum oxide to chelate phosphates

34. Ion selective analyzers using undiluted samples have what advantage over analyzers that use a diluted sample? A. Can measure over a wider range of concentration B. Are not subject to pseudohyponatremia caused by high lipids C. Do not require temperature equilibration D. Require less maintenance

B. Are not subject to pseudohyponatremia caused by high lipids

35. Select the equation describing the potential that develops at the surface of an ion-selective electrode. A. van Deemter equation B. van Slyke equation C. Nernst equation D. Henderson–Hasselbalch equation

C. Nernst equation

36. The reference potential of a silver–silver chloride electrode is determined by the: A. Concentration of the potassium chloride filling solution B. Surface area of the electrode C. Activity of total anion in the paste covering the electrode D. The concentration of silver in the paste covering the electrode

A. Concentration of the potassium chloride filling solution

37. The term RT/nF in the Nernst equation defines the: A. Potential at the ion-selective membrane B. Slope of the electrode C. Decomposition potential D. Isopotential point of the electrode

B. Slope of the electrode

38. The ion-selective membrane used to measure potassium is made of: A. High-borosilicate glass membrane B. Polyvinyl chloride dioctylphenyl phosphonate ion exchanger C. Valinomycin gel D. Calomel

C. Valinomycin gel

39. The response of a sodium electrode to a 10-fold increase in sodium concentration should be: A. A 10-fold drop in potential B. An increase in potential of approximately 60 mV C. An increase in potential of approximately 10 mV D. A decrease in potential of approximately 10 mV

B. An increase in potential of approximately 60 mV

40. Which of the electrodes below is a currentproducing (amperometric) rather than a voltage-producing (potentiometric) electrode? A. Clark electrode B. Severinghaus electrode C. pH electrode D. Ionized calcium electrode

A. Clark electrode

41. Which of the following would cause a “response” error from an ion-selective electrode for sodium when measuring serum but not the calibrator? A. Interference from other electrolytes B. Protein coating the ion-selective membrane C. An overrange in sodium concentration D. Protein binding to sodium ion

B. Protein coating the ion-selective membrane

42. In polarography, the voltage needed to cause depolarization of the cathode is called the: A. Half-wave potential B. Isopotential point C. Decomposition potential D. Polarization potential

C. Decomposition potential

43. Persistent noise from an ion-selective electrode is most often caused by: A. Contamination of sample B. Blocked junction at the salt bridge C. Overrange from high concentration D. Improper calibration

B. Blocked junction at the salt bridge

44. Which element is reduced at the cathode of a Clark polarographic electrode? A. Silver B. Oxygen C. Chloride D. Potassium

B. Oxygen

45. Which of the following statements accurately characterizes the coulometric titration of chloride? A. The indicator electrodes generate voltage B. Constant current must be present across the generator electrodes C. Silver ions are formed at the generator cathode D. Chloride concentration is inversely proportional to titration time

B. Constant current must be present across the generator electrodes

46. In the coulometric chloride titration: A. Acetic acid in the titrating solution furnishes the counter ion for reduction B. The endpoint is detected by amperometry C. The titrating reagent contains a phosphate buffer to keep pH constant D. Nitric acid (HNO3) is used to lower the solubility of AgCl

B. The endpoint is detected by amperometry

47. Which of the following compounds can interfere with the coulometric chloride assay? A. Bromide B. Ascorbate C. Acetoacetate D. Nitrate

A. Bromide

48. All of the following compounds contribute to the osmolality of plasma except: A. Lipids B. Creatinine C. Drug metabolites D. Glucose

A. Lipids

49. One mole per kilogram H2O of any solute will cause all of the following except: A. Lower the freezing point by 1.86°C B. Raise vapor pressure by 0.3 mm Hg C. Raise the boiling point by 0.52°C D. Raise osmotic pressure by 22.4 atm

B. Raise vapor pressure by 0.3 mm Hg

50. What component of a freezing point osmometer measures the sample temperature? A. Thermistor B. Thermocouple C. Capacitor D. Electrode

A. Thermistor

51. What type of measuring circuit is used in a freezing point osmometer? A. Electrometer B. Potentiometer C. Wheatstone bridge D. Thermal conductivity bridge

C. Wheatstone bridge

52. Which measurement principle is employed in a vapor pressure osmometer? A. Seebeck B. Peltier C. Hayden D. Darlington

A. Seebeck

53. The freezing point osmometer differs from the vapor pressure osmometer in that only the freezing point osmometer: A. Cools the sample B. Is sensitive to ethanol C. Requires a thermoelectric module D. Requires calibration with aqueous standards

B. Is sensitive to ethanol

54. The method for measuring iron or lead by plating the metal and then oxidizing it is called: A. Polarography B. Coulometry C. Anodic stripping voltometry D. Amperometry

C. Anodic stripping voltometry

55. The term isocratic is used in high-performance liquid chromatography (HPLC) to mean the: A. Mobile phase is at constant temperature B. Stationary phase is equilibrated with the mobile phase C. Mobile phase consists of a constant solvent composition D. Flow rate of the mobile phase is regulated

C. Mobile phase consists of a constant solvent composition

56. The term reverse phase is used in HPLC to indicate that the mobile phase is: A. More polar than the stationary phase B. Liquid and the stationary phase is solid C. Organic and the stationary phase is aqueous D. A stronger solvent than the stationary phase

A. More polar than the stationary phase

57. What is the primary means of solute separation in HPLC using a C18 column? A. Anion exchange B. Size exclusion C. Partitioning D. Cation exchange

C. Partitioning

58. The most commonly used detector for clinical gas–liquid chromatography (GLC) is based upon: A. Ultraviolet light absorbance at 254 nm B. Flame ionization C. Refractive index D. Thermal conductance

B. Flame ionization

59. What type of detector is used in high-performance liquid chromatography with electrochemical detection (HPLC–ECD)? A. Calomel electrode B. Conductivity electrode C. Glassy carbon electrode D. Polarographic electrode

C. Glassy carbon electrode

60. In gas chromatography, the elution order of volatiles is usually based upon the: A. Boiling point B. Molecular size C. Carbon content D. Polarity

A. Boiling point

61. Select the chemical that is used in most HPLC procedures to decrease solvent polarity. A. Hexane B. Nonane C. Chloroform D. Acetonitrile

D. Acetonitrile

62. In thin-layer chromatography (TLC), the distance the solute migrates divided by the distance the solvent migrates is the: A. tR B. Kd C. Rf D. pK

C. Rf

63. Which reagent is used in thin-layer chromatography (TLC) to extract cocaine metabolites from urine? A. Acid and sodium chloride B. Alkali and organic solvent C. Chloroform and sodium acetate D. Neutral solution of ethyl acetate

B. Alkali and organic solvent

64. What is the purpose of an internal standard in HPLC and GC methods? A. To compensate for variation in extraction and injection B. To correct for background absorbance C. To compensate for changes in flow rate D. To correct for coelution of solutes

A. To compensate for variation in extraction and injection

65. What is the confirmatory method for measuring drugs of abuse? A. HPLC B. Enzyme-multiplied immunoassay technique (EMIT) C. Gas chromatography with mass spectroscopy (GC-MS) D. TLC

C. Gas chromatography with mass spectroscopy (GC-MS)

66. The fragments typically produced and analyzed in methods employing mass spectroscopy are typically: A. Of low molecular size ranging from 10–100 daltons B. Cations caused by electron loss or proton attachment C. Anions caused by bombarding the molecule with an electron source D. Neutral species formed after excited molecules form a stable resonance structure

B. Cations caused by electron loss or proton attachment

67. What component is used in a GC-MS but not used in an LC-MS? A. Electron source B. Mass filter C. Detector D. Vacuum

A. Electron source

68. What process is most often used in LC-MS to introduce the sample into the mass filter? A. Electrospray ionization B. Chemical ionization C. Electron impact ionization D. Fast atom bombardment

A. Electrospray ionization

69. In mass spectroscopy, the term base peak typically refers to: A. The peak with the lowest mass B. The peak with the most abundance C. A natural isotope of the molecular ion D. The first peak to reach the mass detector

B. The peak with the most abundance

70. Which method is the most useful when screening for errors of amino and organic acid metabolism? A. Two-dimensional thin-layer chromatography B. Gas chromatography C. Electrospray ionization tandem-mass spectroscopy D. Inductively charged coupled-mass spectroscopy

C. Electrospray ionization tandem-mass spectroscopy

71. In tandem-mass spectroscopy, the first mass filter performs the same function as: A. The ion source B. The chromatography column C. Extraction D. The vacuum system

B. The chromatography column

72. SITUATION: A GC-MS analysis using nitrogen as the carrier gas shows an extensively noisy baseline. A sample of the solvent used for the extraction procedure, ethyl acetate, was injected and showed the same noise. Results of an Autotune test showed the appearance of a base peak at 16 with two smaller peaks at 17 and 18. These results indicate: A. The solvent is contaminated B. The carrier gas is contaminated C. There is electrical noise in the detector D. The ion source is dirty

B. The carrier gas is contaminated

73. Why is vacuum necessary in the mass filter of a mass spectrometer? A. Ionization does not occur at atmospheric pressure B. It prevents collision between fragments C. It removes electrons from the ion source D. It prevents contamination

B. It prevents collision between fragments

74. What method is used to introduce the sample into a mass spectrometer for analysis of a trace element? A. Electrospray ionization B. Laser desorption C. Inductively charged plasma (ICP) ionization D. Direct injection

C. Inductively charged plasma (ICP) ionization

75. Which component is needed for a thermal cycler to amplify DNA? A. Programmable heating and cooling unit B. Vacuum chamber with zero head space C. Sealed airtight constant-temperature chamber D. Temperature-controlled ionization chamber

A. Programmable heating and cooling unit

76. In real-time PCR, what value is needed in order to determine the threshold? A. Background signal B. Melt temperature C. Maximum fluorescence D. Threshold cycle

A. Background signal

77. Given the following real-time PCR amplification curve, what is the threshold cycle? A. 15 B. 20 C. 25 D. 30

C. 25

78. In addition to velocity, what variable is also needed to calculate the relative centrifugal force (g force) of a centrifuge? A. Head radius B. Angular velocity coefficient C. Diameter of the centrifuge tube D. Ambient temperature in degrees Centigrade

A. Head radius

79. Which of the following situations is likely to cause an error when weighing with an electronic analytical balance? A. Failure to keep the knife edge clean B. Failure to close the doors of the balance before reading the weight C. Oxidation on the surface of the substitution weights D. Using the balance without allowing it to warm up for at least 10 minutes

B. Failure to close the doors of the balance before reading the weight

80. When calibrating a semiautomatic pipet that has a fixed delivery of 10.0 μL using a gravimetric method, what should be the average weight of deionized water transferred? A. 10.0 μg B. 100.0 μg C. 1.0 mg D. 10.0 mg

D. 10.0 mg

Clinical Chemistry- Instrumentation Flashcards

(80 cards)