Medical Laboratory Science Review Chemical Pathology 1a

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ANSWERS AND RATIONAL

1. 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 

2. 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% 

3. 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 

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

5. A green-colored solution would show highest transmittance at: 
A. 475 nm 
B. 525 nm 
C. 585 nm 
D. 620 nm
6. 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 

7. 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 

8. 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 

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

10. 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
11. 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 

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

13. 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 

14. 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 f luctuation 
C. To obviate the need for wavelength adjustment 
D. To reduce stray light effects
15. 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 

16. 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 

17. 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 

18. 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 

19. Which instrument requires a highly regulated DC power supply? 
A. A spectrophotometer with a barrier layer cell 
B. A colorimeter with multilayer interference f ilters
C. A spectrophotometer with a photomultiplier tube 
D. A densitometer with a photodiode detector.
20. 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 

21. 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 

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

23. Which of the following statements about f luorometry is accurate? 
A. Fluorometry is less sensitive than spectrophotometry 
B. Fluorometry is less specific than spectrophotometry 
C. Unsaturated cyclic molecules are often f luorescent 
D. Fluorescence is directly proportional to temperature 

24. Which of the following components is not needed in a chemiluminescent immunoassay analyzer? 
A. Source lamp 
B. Monochromator 
C. Photodetector 
D. Wash station
25. Which substance is used to generate the light signal in electrochemiluminescence? 
A. Acridinium 
B. Luminol 
C. Dioxetane phosphate 
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

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 

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

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
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

31. Interference in atomic absorption spectrophotometry caused by differences in viscosity is called: 
A. Absorption interference 
B. Matrix effect 
C. Ionization interference 
D. Quenching 

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

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 

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
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 

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

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 

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 

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
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



THEN THE NEXT QUESTION WILL BE AVAILABLE HERE

© Medical Laboratory Science Review 4th edition by Robert R. Harr

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