Detailed study of laser enhanced ionization with electrothermal vaporization-flame atomization for trace element analysis

231 Pages·1996·3.6 MB·English

by  Riter, Ken Lynn

ADETAILEDSTUDYOFLASERENHANCEDIONIZATION
WITHELECTROTHERMALVAPORIZATION-FLAME
ATOMIZATIONFORTRACEELEMENTANALYSIS
By
KENLYNNRITER
ADISSERTATIONPRESENTEDTOTHEGRADUATESCHOOL
OFTHEUNIVERSITYOFFLORIDAINPARTIALFULFILLMENT
OFTHE REQUIREMENTS FORTHEDEGREE OF
DOCTOROFPHILOSOPHY
UNIVERSITYOFFLORIDA
1996
Dedicated to the loving memories of my mother, Namiko
(Tamanaha) Riter (September 16, 1936 - July 9, 1983), and
father, Roger LynnRiter (July 12, 1945 - August 10, 1996).
Without their love, encouragement, and support none of this
wouldhavebeenwritten.
ACKNOWLEDGMENTS
First, Iwouldliketo thankDr. JimWinefordner forthe
opportunitytoresearchinhis lab. Although Ihave learned
muchabout laserspectroscopyinJim'slab, hisexampleofhow
tobeadecentpersonandtotreatotherswithrespect iswhat
will alwaysbewithme. IwouldliketothankDr. BenSmith
for all of his advice andhelp in the lab. Settingup the
instrumentationwouldhavebeenanenormoustaskwithoutBen's
help. IwouldliketothankDr. OlegMatveevforworkingwith
meand lendinghis expertise inlaserenhancedionization to
theproject. IhavelearnedsomuchaboutLEI fromOlegina
very short period of time. Oleg's kindness, patience, and
modestyallowedhimtoexplainverydifficult concepts rather
easily.
IwouldliketothankLeahMordohandWendyClevengerfor
assistingwithandperformingmanyof theexperiments forthe
LEISofMg. Others Iwouldlike to thank includeRobGuenard
forhishelpwiththeultrasonicnebulizer, ChesterEastmanin
themachine shop forbuildingthenewLEIburner, andall of
theWinefordnerandHarrisongroupmembers fortheirhelpand
friendship. Iwouldliketothank theNational Institutes of
. .
Healthfor fundingthis research (Grant # 5-R01-GM49638-03)
Onamorepersonalnote, Iwouldlike tothankmyfamily
fortheirloveandencouragement. Thanks to JonDeGnore, Dr.
BillWalden, andDr. WeiHangforbeingsuchgoodfriendsand
making my stay in Gainesville enjoyable. Finally, I would
liketothankmyfiancee, Leah. Withoutherloveandsupport,
IdonotknowhowIwouldhavemadeitthroughthesefinalfew
months
All thanksbe toGod.
TABLEOFCONTENTS
ACKNOWLEDGMENTS iii
LISTOFTABLES viii
LISTOFFIGURES ix
ABSTRACT xii
CHAPTER1
INTRODUCTION 1
Absolute/StandardlessAnalysis 1
AnalysisofReal Samples 5
DeterminationofLeadinWholeBlood 6
IntentofDissertation 7
CHAPTER2
INTRODUCTIONTOLASERENHANCEDIONIZATION 9
TheOptogalvanicEffect 9
General Principles ofLEI 10
AtomizationofSample 11
ExcitationofAtoms 16
Ionization 20
ChargeCollection 20
CHAPTER3
THEORYOFLASERENHANCED IONIZATION 25
Introduction 25
Thermal Ionization 25
ModeliPTnhrgeorcmeoafslseLsaIsoeRnreipzoEanntshiiaobnnlceeRdatfeoIroonfiThzeaarntmiaAoltnomIoninizaatiFolname. .. 223790
Rate-EquationFormalism 30
Degreeof Ionization forTwo-Step
Excitation 33
Density-MatrixFormalism 34
Detectionofthe IonizationSignal 38
One-DimensionalApproximation 39
PointChargeModel 39
ElectrothermalVaporization 40
AbsoluteAnalysis 42
CHAPTER4
REVIEWOFLASERENHANCED IONIZATION 47
Analytical Performanceof Flame-LEI 47
LimitsofDetectionandSensitivities 47
NoiseandInterferences 58
ApplicationsofLEI toRealSamples 61
DDeetteerrmmiinnaattiioonnssWWiitthhouItnteIrnfteerrafnetranRtemoRveamlova.l..... 6626
HybridEleTcetcrhontihqeuersmalanVdapNoorni-zFelrasmeAtomReservoirs . .7711
HybridCombinationsofFlameand
ElectrothermalVaporizers 74
LEI inthe InductivelyCoupledPlasma 79
OtherMethodsandReservoirs 8
CHAPTER5
EXPERIMENTAL 83
LEI 83
Burners 83
Graphite Furnace 88
FlamePrGaoscedFulrowes,anVdelCoocnidtiyt,ionasndTemperature .... 10937
NoiseStudy 105
FluorescenceDipandFluorescenceProfileof Flame 108
TransportEfficiency 113
TransimpedanceAmplifierCalibration 118
AtomizationEfficiencyMeasurement 119
CHAPTER6
RESULTSANDDISCUSSION 124
LEIofMagnesium 124
MagnesiumAsAnalyte 124
MgLEI Signal 127
SystemParameterOptimizations forOldBurner
Design 130
FlameProfileWithOldBurner 138
Analytical CurveWithOldBurner 138
NewBurnerDesign 145
SystemParameterOptimizationsWithNew
Burner 148
Flame ProfileWithNewBurner 157
MatrixModifier/Carrier 166
AnalyticalCurveWithNewBurner 169
FlameTemperatureandFlameGasVelocity
WiththeNewBurner 174
AbsoluteAnalysis 176
VaporizationEfficiency 176
Transport Efficiency 176
ProbingEfficiency 178
DetectionEfficiency 186
AtomizationEfficiency 187
LEI ofLead 190
ExcitationScheme forLead 190
Carrier 191
CalibrationBehavior 200
CHAPTER7
CONCLUSIONS 202
AbsoluteAnalysis 202
Pb inBlood 203
FutureWork 203
REFERENCES 205
BIOGRAPHICALSKETCH 216
LISTOFTABLES
Table &aS£
1. LEI limits ofdetection 48
2. Graphite furnacetemperatureprogramfor
magnesium 99
3. Graphite furnace temperatureprogramforleadin
blood 102
4. Valuesusedfor flametemperaturecalculation . . 175
5. Mgconcentrationindifferent cottonsamples . . 177
6. EnhancementofLEI signal fordifferenttwo-step
excitationschemes forlead 192
LISTOFFIGURES
Fi.aure Efi3£
1. Processes neededfor laserenhancedionization
spectrometry 13
2. Typical experimental setup for flame-LEI 15
3. oTa)nyepi-ocsnatele-psteexepcxictieatxtacitioitnoantisoucnhseimnuegssinuglftorrvaivsLiiEIoblleestpelcilgtihrgtho,ts,cobp)cy),
tewxoc-isttaetpionexc(iitnadtiireocnt)(,diraencdt)e), dt)hretew-os-tsetpep
excitation 19
4. Various electrode arrangementsusedforLEI
spectroscopy, a) split-cathoderodarrangement,
b) split-cathodeplatearrangement, c)water-
cooled, immersedcathodearrangement, d) water-
cooledcoiledcathodearrangement 22
5. Schematicrepresentationofvarious excitation
anddeexcitationprocesses inathree-level atom:
ncto1h(lrelnei2s,iloeanvnaedllsn,d3eaerrxeecsiptethcaettiivnoeunlmyba;enrdkd2slepnoisnsittatinhteeeosussuomfemotifhsestihoen
c2refl((;oamarB=tlsioU32elemsvkUsri(s3Vrvsil(l3ovio2beln3)onevi2)netg)(alwh)rkalte2aireat3ieorneenesx)(tcl2hti)iaee;hstvneeadsltBtpsaihU12eboevUcsn(2vtvoc(2rrv1oara1p)anl2lttdl)iei(oi=s1(nUr;ibBvr2oe3(anatUkvdanw1v12i2lde()ave)i2nns3isc)toae)inltnsmeihdauvzeonleaUfdaltvtsi(Btevoh22dn113eU)var(navdt21e) 32
6. Blockdiagramoftheexperimental setup forLEIS . 85
7. FirstburnerdesignusedforLEIS 87
8. pDoisaigtriaomnofofnetwhebuhirgnhervodletsaiggenweiltehctrroedleatiavnedlaser
beams 90
9. Detaileddrawingofthenewburnerdesign 92
10. Cut-awayviewofthegraphite furnace showingthe
tantalumsampleextractioninterface 96
11. Sketchoflaboratoryconstructedultrasonic
nebulizerused 107
12. Blockdiagramofexperimental setupfor
monitoringofbothfluorescence andLEI signals . 112
13. Sketchofexperimental setup fortransport
efficiencymeasurement 116
14. Blockdiagramoftheexperimental setup forthe
determinationofthe atomizationefficiency for
Mgbyatomicabsorption 122
15. Oscilloscopetraceofthe laserbeamtiming . . . 126
16. Typical LEI signal formagnesiumwitholder
burner 129
17. Argon flowrateoptimization forMgwitholder
burner 133
18. Burner-to-electrodedistanceoptimization forMg
witholderburner 135
19. Appliedvoltageoptimization forMgwitholder
burner 137
20. Horizontalprofileof the flamewiththeolder
burner 140
21. Analyticalcurve forMgwiththeolderburner . . 142
22. Log-Logplotoftheanalytical curveofFigure 21 144
23. Noises for thehydrogen/air andacetylene/air
flameswiththeolderburnerdesign 147
24. Comparisonofthenoises for thenewandold
burnerdesigns 150