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CLINICAL CHEMISTY (HARR) > Instrumentation > Flashcards

Instrumentation Flashcards

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1
Q

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

A

D

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2
Q

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%

A

B

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3
Q

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

A

D

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4
Q

Which wavelength would be absorbed strongly by a red-colored solution?
A. 450 nm
B. 585 nm
C. 600 nm
D. 650 nm

A

A

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5
Q

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

A

B

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6
Q

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

A

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7
Q

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

A

D

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8
Q

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

A

D

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9
Q

Which photodetector is most sensitive to low levels of light?
A. Barrier layer cell
B. Photodiode
C. Diode array
D. Photomultiplier tube

A

D

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10
Q

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

A

C

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11
Q

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

A

C

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12
Q

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

A

D

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13
Q

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

A

B

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14
Q

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

A

B

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15
Q

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

A

C

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16
Q

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

A

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17
Q

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

A

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18
Q

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

A

C

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19
Q

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

A

C

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20
Q

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

A

C

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21
Q

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

A

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22
Q

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

A

C

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23
Q

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

A

C

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24
Q

Which of the following components is not needed
in a chemiluminescent immunoassay analyzer?
A. Source lamp
B. Monochromator
C. Photodetector
D. Wash station

A

A

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25
Which substance is used to generate the light signal in electrochemiluminescence? A. Acridinium B. Luminol C. Dioxetane phosphate D. Ruthenium
D
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
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
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
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
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
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
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
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
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
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
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
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
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
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
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
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 ions
B
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
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
44
Which element is reduced at the cathode of a Clark polarographic electrode? A. Silver B. Oxygen C. Chloride D. Potassium
B
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
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
47
Which of the following compounds can interfere with the coulometric chloride assay? A. Bromide B. Ascorbate C. Acetoacetate D. Nitrate
A
48
All of the following compounds contribute to the osmolality of plasma except: A. Lipids B. Creatinine C. Drug metabolites D. Glucose
A
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
50
What component of a freezing point osmometer measures the sample temperature? A. Thermistor B. Thermocouple C. Capacitor D. Electrode
A
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
52
Which measurement principle is employed in a vapor pressure osmometer? A. Seebeck B. Peltier C. Hayden D. Darlington
A
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
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
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
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
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
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
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
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
61
Select the chemical that is used in most HPLC procedures to decrease solvent polarity. A. Hexane B. Nonane C. Chloroform D. Acetonitrile
D
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
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
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
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
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
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
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
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
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
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
C
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
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
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
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
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
77
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
78
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
79
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

CLINICAL CHEMISTY (HARR) (8 decks)

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