HARR CLINICAL CHEMISTRY
QUESTIONS WITH 100% COMPLETE
DETAILED ANSWERS
Which rformula rcorrectly rdescribes rthe rrelationship rbetween rabsorbance rand r%T r?
A. rA r= r2 r- rlog r%T
B. rA r= rlog r1/T
C. rA r= r-log rT
D. rAll rof rthese roptions r- rCORRECT✅✅D. rAll rof rthese roptions
D rAbsorbance ris rproportional rto rthe rinverse rlog rof rtransmittance.
A r= r-log rT r= rlog r1/T
Multiplying rthe rnumerator rand rdenominator
by r100 rgives:
A r= rlog r(100/100 rX rT)
100 rX rT r= r%T, r
substituting r%T rfor r100 rX rT rgives:
A r= rlog r100/%T
A r= rlog r100 r- rlog r%T
A r= r2.0 r- rlog r%T
For rexample, rif r%T r= r10.0, rthen:
A r= r2.0 r- rlog r10.0
log r10.0 r= r1.0
A r= r2.0-1.0 r= r1.0
A rsolution rthat rhas ra rtransmittance rof r1.0 r%T rwould rhave ran rabsorbance rof:
A. r1.0
B. r2.0
C. r1%
D. r99% r- rCORRECT✅✅B. r2.0
B
A r= r2.0 r- rlog r%T
A r= r2.0 r- rlog r1.0
The rlog rof r1.0 r= r0
A r= r2.0
In rabsorption rspectrophotometry:
A. rAbsorbance ris rdirectly rproportional rto
,transmittance
B. rPercent rtransmittance ris rdirectly rproportional rto rconcentration
C. rPercent rtransmittance ris rdirectly rproportional rto rthe rlight rpath rlength
D. rAbsorbance ris rdirectly rproportional rto rconcentration r- rCORRECT✅✅D.
rAbsorbance ris rdirectly rproportional rto rconcentration
D rBeer's rlaw rstates rthat rA r= ra r× rb r× rc, rwhere ra ris rthe rabsorptivity rcoefficient r(a
rconstant), rb ris rthe rpath rlength, rand rc ris rconcentration. rAbsorbance ris rdirectly
rproportional rto rboth rb rand rc. rDoubling rthe rpath rlength rresults rin rincident rlight
rcontacting rtwice rthe rnumber rof rmolecules rin rsolution. rThis rcauses rabsorbance rto
rdouble, rthe rsame reffect ras rdoubling rthe rconcentration rof rmolecules.
Which rwavelength rwould rbe rabsorbed rstrongly rby ra rred-colored rsolution?
A. r450 rnm
B. r585 rnm
C. r600 rnm
D. r650 rnm r- rCORRECT✅✅A. r450 rnm
A rA rsolution rtransmits rlight rcorresponding rin rwavelength rto rits rcolor, rand rusually
rabsorbs rlight rof rwavelengths rcomplementary rto rits rcolor. rA rred rsolution rtransmits
rlight rof r600-650 rnm rand rstrongly rabsorbs r400-500 rnm rlight.
A rgreen-colored rsolution rwould rshow rhighest rtransmittance rat:
A. r475 rnm
B. r525 rnm
C. r585 rnm
D. r620 rnm r- rCORRECT✅✅B. r525 rnm
B rGreen rlight rconsists rof rwavelengths rfrom r500-550 rnm. rA rgreen-colored rsolution
rwith ra rtransmittance rmaximum rof r525 rnm rand ra r50-nm rbandpass rtransmits rlight rof
r525 rnm rand rabsorbs rlight rbelow r475 rnm rand rabove r575 rnm. rA rsolution rthat ris
rgreen rwould rbe rquantitated rusing ra rwavelength rthat rit rabsorbs rstrongly, rsuch ras
r450 rnm.
SITUATION: rA rtechnologist ris rperforming ran renzyme rassay rat r340 rnm rusing ra
rvisible-range rspectrophotometer. rAfter rsetting rthe rwavelength rand radjusting rthe
rreadout rto rzero r%T rwith rthe rlight rpath rblocked, ra rcuvette rwith rdeionized rwater ris
rinserted. rWith rthe rlight rpath rfully ropen rand rthe r100%T rcontrol rat rmaximum, rthe
rinstrument rreadout rwill rnot rrise rabove r90%T. rWhat ris rthe rmost rappropriate rfirst
rcourse rof raction?
A. rReplace rthe rsource rlamp
B. rInsert ra rwider rcuvette rinto rthe rlight rpath
C. rMeasure rthe rvoltage racross rthe rlamp rterminals
,D. rReplace rthe rinstrument rfuse r- rCORRECT✅✅A. rReplace rthe rsource rlamp
A rVisible rspectrophotometers rare rusually rsupplied rwith ra rtungsten ror rquartz rhalogen
rsource rlamp. rTungsten rlamps rproduce ra rcontinuous rrange rof rwavelengths rfrom
rabout r320-2,000 rnm. rOutput rincreases ras rwavelength rbecomes rlonger rpeaking rat
raround r1,000 rnm, rand ris rpoor rbelow r400 rnm. rAs rthe rlamp renvelope rdarkens rwith
rage, rthe ramount rof rlight rreaching rthe rphotodetector rat r340 rnm rbecomes rinsufficient
rto rset rthe rblank rreading rto r100%T. rQuartz rhalogen rlamps rproduce rlight rfrom r300
rnm rthrough rthe rinfrared rregion. rDeuterium ror rhydrogen rlamps rproduce rultraviolet-
rich rspectra roptimal rfor rultraviolet r(UV) rwork. rMercury rvapor rlamps rproduce ra
rdiscontinuous rspectrum rthat rincludes ra rhigh routput rat raround r365 rnm rthat ris ruseful
rfor rfluorescent rapplications. rXenon rlamps rgenerate ra rcontinuous rspectrum rof rfairly
runiform rintensity rfrom r300-2,000 rnm, rmaking rthem ruseful rfor rboth rvisible rand rUV
rapplications.
Which rtype rof rmonochromator rproduces rthe rpurest rmonochromatic rlight rin rthe rUV
rrange?
A. rA rdiffraction rgrating rand ra rfixed rexit rslit
B. rA rsharp rcutoff rfilter rand ra rvariable rexit rslit
C. rInterference rfilters rand ra rvariable rexit rslit
D. rA rprism rand ra rvariable rexit rslit r- rCORRECT✅✅D. rA rprism rand ra rvariable rexit
rslit
D rDiffraction rgratings rand rprisms rboth rproduce ra rcontinuous rrange rof rwavelengths.
rA rdiffraction rgrating rproduces ra runiform rseparation rof rwavelengths. rA rprism
rproduces rmuch rbetter rseparation rof rhigh-frequency rlight rbecause rrefraction ris
rgreater rfor rhigher-energy rwavelengths. rInstruments rusing ra rprism rand ra rvariable rexit
rslit rcan rproduce rUV rlight rof ra rvery rnarrow rbandpass. rThe radjustable rslit ris rrequired
rin rorder rto rallow rsufficient rlight rto rreach rthe rdetector rto rset r100%T.
Which rmonochromator rspecification ris rrequired rin rorder rto rmeasure rthe rtrue
rabsorbance rof ra rcompound rhaving ra rnatural rabsorption rbandwidth rof r30 rnm?
A. r50-nm rbandpass
B. r25-nm rbandpass
C. r15-nm rbandpass
D. r5-nm rbandpass r- rCORRECT✅✅D. r5-nm rbandpass
D rBandpass rrefers rto rthe rrange rof rwavelengths rpassing rthrough rthe rsample. rThe
rnarrower rthe rbandpass, rthe rgreater rthe rphotometric rresolution. rBandpass rcan rbe
rmade rsmaller rby rreducing rthe rwidth rof rthe rexit rslit. rAccurate rabsorbance
rmeasurements rrequire ra rbandpass rless rthan rone-fifth rthe rnatural rbandpass rof rthe
rchromophore
Which rphotodetector ris rmost rsensitive rto rlow rlevels rof rlight?
, A. rBarrier rlayer rcell
B. rPhotodiode
C. rDiode rarray
D. rPhotomultiplier rtube r- rCORRECT✅✅D. rPhotomultiplier rtube
D rThe rphotomultiplier rtube ruses rdynodes rof rincreasing
voltage rto ramplify rthe rcurrent rproduced rby rthe rphotosensitive rcathode. rIt ris r10,000
rtimes ras rsensitive ras ra rbarrier rlayer rcell, rwhich rhas rno ramplification. rA
rphotomultiplier rtube rrequires ra rDC-regulated rlamp rbecause rit rresponds rto rlight
rfluctuations rcaused rby rthe rAC rcycle.
Which rcondition ris ra rcommon rcause rof rstray rlight?
A. rUnstable rsource rlamp rvoltage
B. rImproper rwavelength rcalibration
C. rDispersion rfrom rsecond-order rspectra
D. rMisaligned rsource rlamp r- rCORRECT✅✅C. rDispersion rfrom rsecond-order
rspectra
C rStray rlight ris rcaused rby rthe rpresence rof rany rlight rother rthan rthe rwavelength rof
rmeasurement rreaching rthe rdetector. rIt ris rmost roften rcaused rby rsecond-order
rspectra, rdeteriorated roptics, rlight rdispersed rby ra rdarkened rlamp renvelope, rand
rextraneous rroom rlight.
A rlinearity rstudy ris rperformed ron ra rvisible rspectrophotometer rat r650 rnm rand rthe
rfollowing rabsorbance rreadings rare robtained:
Concentration rof rStandard r
10.0 rmg/dL r
20.0 rmg/dL r
30.0 rmg/dL r
40.0 rmg/dL r
50.0 rmg/dL r
Absorbance
0.20
0.41
0.62
0.79
0.92
The rstudy rwas rrepeated rusing rfreshly rprepared rstandards rand rreagents, rbut rresults
rwere ridentical rto rthose rshown. rWhat ris rthe rmost rlikely rcause rof
these rresults?
A. rWrong rwavelength rused
B. rInsufficient rchromophore rconcentration
QUESTIONS WITH 100% COMPLETE
DETAILED ANSWERS
Which rformula rcorrectly rdescribes rthe rrelationship rbetween rabsorbance rand r%T r?
A. rA r= r2 r- rlog r%T
B. rA r= rlog r1/T
C. rA r= r-log rT
D. rAll rof rthese roptions r- rCORRECT✅✅D. rAll rof rthese roptions
D rAbsorbance ris rproportional rto rthe rinverse rlog rof rtransmittance.
A r= r-log rT r= rlog r1/T
Multiplying rthe rnumerator rand rdenominator
by r100 rgives:
A r= rlog r(100/100 rX rT)
100 rX rT r= r%T, r
substituting r%T rfor r100 rX rT rgives:
A r= rlog r100/%T
A r= rlog r100 r- rlog r%T
A r= r2.0 r- rlog r%T
For rexample, rif r%T r= r10.0, rthen:
A r= r2.0 r- rlog r10.0
log r10.0 r= r1.0
A r= r2.0-1.0 r= r1.0
A rsolution rthat rhas ra rtransmittance rof r1.0 r%T rwould rhave ran rabsorbance rof:
A. r1.0
B. r2.0
C. r1%
D. r99% r- rCORRECT✅✅B. r2.0
B
A r= r2.0 r- rlog r%T
A r= r2.0 r- rlog r1.0
The rlog rof r1.0 r= r0
A r= r2.0
In rabsorption rspectrophotometry:
A. rAbsorbance ris rdirectly rproportional rto
,transmittance
B. rPercent rtransmittance ris rdirectly rproportional rto rconcentration
C. rPercent rtransmittance ris rdirectly rproportional rto rthe rlight rpath rlength
D. rAbsorbance ris rdirectly rproportional rto rconcentration r- rCORRECT✅✅D.
rAbsorbance ris rdirectly rproportional rto rconcentration
D rBeer's rlaw rstates rthat rA r= ra r× rb r× rc, rwhere ra ris rthe rabsorptivity rcoefficient r(a
rconstant), rb ris rthe rpath rlength, rand rc ris rconcentration. rAbsorbance ris rdirectly
rproportional rto rboth rb rand rc. rDoubling rthe rpath rlength rresults rin rincident rlight
rcontacting rtwice rthe rnumber rof rmolecules rin rsolution. rThis rcauses rabsorbance rto
rdouble, rthe rsame reffect ras rdoubling rthe rconcentration rof rmolecules.
Which rwavelength rwould rbe rabsorbed rstrongly rby ra rred-colored rsolution?
A. r450 rnm
B. r585 rnm
C. r600 rnm
D. r650 rnm r- rCORRECT✅✅A. r450 rnm
A rA rsolution rtransmits rlight rcorresponding rin rwavelength rto rits rcolor, rand rusually
rabsorbs rlight rof rwavelengths rcomplementary rto rits rcolor. rA rred rsolution rtransmits
rlight rof r600-650 rnm rand rstrongly rabsorbs r400-500 rnm rlight.
A rgreen-colored rsolution rwould rshow rhighest rtransmittance rat:
A. r475 rnm
B. r525 rnm
C. r585 rnm
D. r620 rnm r- rCORRECT✅✅B. r525 rnm
B rGreen rlight rconsists rof rwavelengths rfrom r500-550 rnm. rA rgreen-colored rsolution
rwith ra rtransmittance rmaximum rof r525 rnm rand ra r50-nm rbandpass rtransmits rlight rof
r525 rnm rand rabsorbs rlight rbelow r475 rnm rand rabove r575 rnm. rA rsolution rthat ris
rgreen rwould rbe rquantitated rusing ra rwavelength rthat rit rabsorbs rstrongly, rsuch ras
r450 rnm.
SITUATION: rA rtechnologist ris rperforming ran renzyme rassay rat r340 rnm rusing ra
rvisible-range rspectrophotometer. rAfter rsetting rthe rwavelength rand radjusting rthe
rreadout rto rzero r%T rwith rthe rlight rpath rblocked, ra rcuvette rwith rdeionized rwater ris
rinserted. rWith rthe rlight rpath rfully ropen rand rthe r100%T rcontrol rat rmaximum, rthe
rinstrument rreadout rwill rnot rrise rabove r90%T. rWhat ris rthe rmost rappropriate rfirst
rcourse rof raction?
A. rReplace rthe rsource rlamp
B. rInsert ra rwider rcuvette rinto rthe rlight rpath
C. rMeasure rthe rvoltage racross rthe rlamp rterminals
,D. rReplace rthe rinstrument rfuse r- rCORRECT✅✅A. rReplace rthe rsource rlamp
A rVisible rspectrophotometers rare rusually rsupplied rwith ra rtungsten ror rquartz rhalogen
rsource rlamp. rTungsten rlamps rproduce ra rcontinuous rrange rof rwavelengths rfrom
rabout r320-2,000 rnm. rOutput rincreases ras rwavelength rbecomes rlonger rpeaking rat
raround r1,000 rnm, rand ris rpoor rbelow r400 rnm. rAs rthe rlamp renvelope rdarkens rwith
rage, rthe ramount rof rlight rreaching rthe rphotodetector rat r340 rnm rbecomes rinsufficient
rto rset rthe rblank rreading rto r100%T. rQuartz rhalogen rlamps rproduce rlight rfrom r300
rnm rthrough rthe rinfrared rregion. rDeuterium ror rhydrogen rlamps rproduce rultraviolet-
rich rspectra roptimal rfor rultraviolet r(UV) rwork. rMercury rvapor rlamps rproduce ra
rdiscontinuous rspectrum rthat rincludes ra rhigh routput rat raround r365 rnm rthat ris ruseful
rfor rfluorescent rapplications. rXenon rlamps rgenerate ra rcontinuous rspectrum rof rfairly
runiform rintensity rfrom r300-2,000 rnm, rmaking rthem ruseful rfor rboth rvisible rand rUV
rapplications.
Which rtype rof rmonochromator rproduces rthe rpurest rmonochromatic rlight rin rthe rUV
rrange?
A. rA rdiffraction rgrating rand ra rfixed rexit rslit
B. rA rsharp rcutoff rfilter rand ra rvariable rexit rslit
C. rInterference rfilters rand ra rvariable rexit rslit
D. rA rprism rand ra rvariable rexit rslit r- rCORRECT✅✅D. rA rprism rand ra rvariable rexit
rslit
D rDiffraction rgratings rand rprisms rboth rproduce ra rcontinuous rrange rof rwavelengths.
rA rdiffraction rgrating rproduces ra runiform rseparation rof rwavelengths. rA rprism
rproduces rmuch rbetter rseparation rof rhigh-frequency rlight rbecause rrefraction ris
rgreater rfor rhigher-energy rwavelengths. rInstruments rusing ra rprism rand ra rvariable rexit
rslit rcan rproduce rUV rlight rof ra rvery rnarrow rbandpass. rThe radjustable rslit ris rrequired
rin rorder rto rallow rsufficient rlight rto rreach rthe rdetector rto rset r100%T.
Which rmonochromator rspecification ris rrequired rin rorder rto rmeasure rthe rtrue
rabsorbance rof ra rcompound rhaving ra rnatural rabsorption rbandwidth rof r30 rnm?
A. r50-nm rbandpass
B. r25-nm rbandpass
C. r15-nm rbandpass
D. r5-nm rbandpass r- rCORRECT✅✅D. r5-nm rbandpass
D rBandpass rrefers rto rthe rrange rof rwavelengths rpassing rthrough rthe rsample. rThe
rnarrower rthe rbandpass, rthe rgreater rthe rphotometric rresolution. rBandpass rcan rbe
rmade rsmaller rby rreducing rthe rwidth rof rthe rexit rslit. rAccurate rabsorbance
rmeasurements rrequire ra rbandpass rless rthan rone-fifth rthe rnatural rbandpass rof rthe
rchromophore
Which rphotodetector ris rmost rsensitive rto rlow rlevels rof rlight?
, A. rBarrier rlayer rcell
B. rPhotodiode
C. rDiode rarray
D. rPhotomultiplier rtube r- rCORRECT✅✅D. rPhotomultiplier rtube
D rThe rphotomultiplier rtube ruses rdynodes rof rincreasing
voltage rto ramplify rthe rcurrent rproduced rby rthe rphotosensitive rcathode. rIt ris r10,000
rtimes ras rsensitive ras ra rbarrier rlayer rcell, rwhich rhas rno ramplification. rA
rphotomultiplier rtube rrequires ra rDC-regulated rlamp rbecause rit rresponds rto rlight
rfluctuations rcaused rby rthe rAC rcycle.
Which rcondition ris ra rcommon rcause rof rstray rlight?
A. rUnstable rsource rlamp rvoltage
B. rImproper rwavelength rcalibration
C. rDispersion rfrom rsecond-order rspectra
D. rMisaligned rsource rlamp r- rCORRECT✅✅C. rDispersion rfrom rsecond-order
rspectra
C rStray rlight ris rcaused rby rthe rpresence rof rany rlight rother rthan rthe rwavelength rof
rmeasurement rreaching rthe rdetector. rIt ris rmost roften rcaused rby rsecond-order
rspectra, rdeteriorated roptics, rlight rdispersed rby ra rdarkened rlamp renvelope, rand
rextraneous rroom rlight.
A rlinearity rstudy ris rperformed ron ra rvisible rspectrophotometer rat r650 rnm rand rthe
rfollowing rabsorbance rreadings rare robtained:
Concentration rof rStandard r
10.0 rmg/dL r
20.0 rmg/dL r
30.0 rmg/dL r
40.0 rmg/dL r
50.0 rmg/dL r
Absorbance
0.20
0.41
0.62
0.79
0.92
The rstudy rwas rrepeated rusing rfreshly rprepared rstandards rand rreagents, rbut rresults
rwere ridentical rto rthose rshown. rWhat ris rthe rmost rlikely rcause rof
these rresults?
A. rWrong rwavelength rused
B. rInsufficient rchromophore rconcentration
