CHEM 311 (INSTRUMENTAL ANALYTICAL CHEMISTRY): FINAL QUESTIONS AND CORRECT ANSWERS

CHEM 311 (INSTRUMENTAL
ANALYTICAL CHEMISTRY): FINAL
QUESTIONS AND CORRECT
ANSWERS
hollowA2cathodeA2lampA2(excitationA2sourceA2forA2atomicA2spectrometry)A2-A2Ans--
(1)A2ΔEA2=A2300A2VA2ionizesA2inertA2gas,A2suchA2asA2neonA2orA2argon;
(2)A2CationsA2ofA2inertA2gasA2strikeA2cathode,A2creatingA2excitedA2atoms;
(3)A2ExcitedA2atomsA2relaxA2throughA2emission

flameA2(atomizerA2forA2atomicA2absorptionA2spectrometry)A2-A2Ans--
(AAS)A2AtomizationA2ofA2metalA2solutionsA2thatA2formA2stableA2oxidesA2orA2burnA2fuel-
richA2usingA2laminarA2flowA2burnerA2withA2oxidant/
fuelA2flowA2regulatorsA2andA2baffles:A2pathA2lengthA2isA2lengthA2ofA2flameA2(5A2-
A210A2cm)A2withA2TA2(air)A2=A21700A2-A22400A2^oCA2andA2TA2(O2,A2NO2)A2=A22500A2-
A23100A2^oC


ADVANTAGE
Continuous

DISADVANTAGE
FlameA2positionA2mustA2beA2optimizedA2forA2eachA2analyte,A2e.g.:A2CrA2immediatelyA2form
sA2stableA2oxides,A2decreasingA2absorbance;A2MgA2requiresA2increasedA2temperatureA2bu
tA2formsA2oxidesA2atA2secondaryA2combustionA2zone;A2AgA2doesA2notA2oxidize

hydrideA2generationA2(sampleA2introductionA2forA2atomicA2spectrometry)A2-A2Ans--
SampleA2introductionA2ofA2As,A2Sb,A2Sn,A2Bi,A2PbA2solutions:A2
(1)A2AddA2*acidifiedA2aqueousA2sampleA2solution*A2toA2*1%A2aqueousA2sodiumA2borohydri
de*A2(NaBH4)A2containedA2inA2glassA2vessel,A2generatingA2volatileA2hydrides;A2
(2)A2VolatileA2hydridesA2areA2sweptA2intoA2atomizationA2chamberA2byA2inertA2gas;A2
(3)A2SilicaA2tubeA2atomizationA2chamberA2isA2heatedA2toA2severalA2hundredA2degreesA2byA
2flameA2orA2furnace,A2decomposingA2hydrideA2andA2formingA2atoms


ADVANTAGE
IncreasedA2detectionA2limitsA2(10A2-A2100X)

DISADVANTAGE
ToxicA2chemicalA2species

, solidA2electrothermalA2vaporizationA2(orA2graphiteA2furnace)A2(sampleA2introductionA2forA2
atomicA2spectrometry)A2-A2Ans--
SolidA2sampleA2introductionA2usingA2heatedA2graphiteA2tube:A2
(1)A2SolventA2isA2evaporated;A2
(2)A2SampleA2isA2ashed,A2atomizationA2viaA2plume

ADVANTAGE
SmallA2sampleA2volumesA2withoutA2sampleA2preparationA2butA2withA2discreteA2signalA2duri
ngA2aspirationA2→A2sensitive

sparkA2ablationA2(sampleA2introductionA2forA2atomicA2spectrometry)A2-A2Ans--Conducting-
solidA2sampleA2introductionA2throughA2thermalA2ionizationA2usingA2highA2potentialA2differe
nceA2betweenA2twoA2electrodesA2atA2TA2=A240A2000A2K

ADVANTAGE
PortableA2devices,A2e.g.A2scrapA2yardsA2forA2metalA2identification

DISADVANTAGE
FrequentA2replacementA2ofA2electrodes

arcA2ablationA2(sampleA2introductionA2forA2atomicA2spectrometry)A2-A2Ans--Conducting-
solidA2sampleA2introductionA2throughA2thermalA2ionizationA2usingA2highA2potentialA2differe
nceA2betweenA2twoA2electrodesA2atA2TA2=A24A2000A2-A25A2000A2K

DISADVANTAGE
ArcA2wandering;A2frequentA2replacementA2ofA2electrodes

Smith-HieftjeA2methodA2-A2Ans--
CorrectionA2methodA2forA2spectralA2interferences,A2typicallyA2usedA2inA2conjunctionA2withA
2modulatedA2powerA2sourceA2setup:A2
(1)A2OperateA2atA2lowA2currentA2HCL,A2acquiringA2narrowA2bandwidthA2output;
(2)A2OperateA2atA2highA2currentA2HCL,A2acquiringA2largerA2bandwidthA2outputA2withA2self-
absorptionA2atA2cathodeA2(central),A2wavelengthsA2atA2sidesA2areA2notA2absorbedA2butA2sc
attered;
(3)A2CorrectA2absorbanceA2measurement

inductively-coupledA2plasmaA2(ICP)A2(atomizerA2forA2atomicA2emissionA2spectrometry)A2-
A2Ans--(AES)A2AtomizationA2throughA2argonA2plasmaA2usingA2TeslaA2andA2radio-
frequencyA2inductionA2coilsA2atA2TA2=A24A2000A2-A28A2000A2K

ADVANTAGES
ChemicallyA2inertA2matrixA2withA2reducedA2spectralA2interferencesA2givenA2transparencyA2
ofA2plasmaA21A2-
A23A2cmA2aboveA2inductionA2coils,A2andA2reducedA2chemicalA2interferencesA2givenA2extre
meA2temperatureA2(withA2consistentA2temperatureA2profileA2inA2comparisonA2toA2flameA2so