Design and development of a microcavity hollow cathode glow discharge emission system for simultaneous multielement analysis of discrete nanosamples of solution residues

178 Pages·1993·1.4 MB·English

by  Morgan, Cheryl

DSEISCMIAUGTLNHTAOANNDNADEENOGDOULESSVOAMEMWULPLDOLTIPESIMSCEEHOLNAFETRMSGOEOEFNLTUEAMTAIMINSIOASCNLIRYROOSNECISASSIVYDOISUFTTEYESDMIHSOFCOLRRLETOEW
CHERYLMORGAN
OAFTDIHSESOUEFNRITTVAHTEEIROSRNIEDTQPOYURCIOETRFSOEEFRMNLETOONEFRTDISPDTHAFOIOILTRNOHSTPEOHAPGREHRTDYIAEADGLURFAEUTELEFOSIFCLHLOMOENLT
UNIVERSITYOFFLORIDA
1993
UNIVERSITYOFFLORIDALIBRARIES
ToWill,DaleandBarney-thanksforkeepingmyspiritsup
ACKNOWLEDGMENTS
studiesItatisthweitUhniavegrresaittyseonfseFloofriadca.comApligsrhamdeuantteadnedgrpereideinthcahtemIifsitnriyshsucepntmeyd
almostanimpossibledream5or6yearsago.Butwithagreatdealof
encouragementfrommyundergraduatechemistryprofessors.Dr.DavidBurgess
andDr.WilliamTotherow,Itooktheplungeandenteredgraduateschoolinthe
Gfaallgnoofn,19h89o.wcIotuhladsInhoatvaelgwiavyesnbuepe?neMaysyffaomrilmyehabsutshwiotwhnfmrieenadsgrleiaktedReaaclheolf
support.Myparents,EllieandBingLonnroth,helpedmegetofftoagoodstart
inFlorida.MychildrenLaurieandBrianhavestayedbymysideandhavegiven
methreebeautifulgrandchildren-Alexis.AndrewandJamie.Mywonderful
grandmother,EvelynLeard,hasbeenasaint(Iloveyou!).Myhusband.Will
Morgan,hasbeenananchorforme.Hisundyingloveandsupportarewithme
daily.Mybrother.DaleLonnroth,hasbeenmynumberonecheerleader.His
faithinmethroughouttheyearshassustainedmyspiritandfocusedmyenergies.
Mythankstoagreatfriend.
Inadditiontomyfamilyandfriends,Igratefullyacknowledgethesupport
andencouragementfrommyadvisorsandcoworkers.Mysincerethanksgotomy
researchadvisor.Dr.JimWinefordner.forhisguidanceandsupportofmy
research.IwouldalsoliketothankBenSmith.Hisexperimentalexpertisewas
invaluable.CherylDaviswasagreathelpandsupportwiththisproject.Bill
Spencergraciouslyallowedmetosharethephotodiodearraysystemwithhim.
ItwasapleasuretoworkalongsideMikeWcnsinginCLB207.Finally,thanks
gotoBenWomackwhotookmeunderhiswingwhenIfirstjoinedthegroup.
Ithasbeenagreatresearchgrouptoworkwith.
TABLEOFCONTENTS
ACKNOWLEDGMENTS
ABSTRACT
CHAPTERS
1INTRODUCTION 1
4OHRSiecvIscoenteprsonetrvtiriocueDafmwleeDnvoiDtesfealstvIoeiehrpoeltmnaoeGtpnilmtooenswnitDniHsoclhlarogweCathodeGlowDischarge 4g1I1
2LOWPRESSUREDISCHARGES 13
CCDaaittshhcohodadirecgeGSepFouemtateteutrrrieynsgandCharacteristics 331153
3MDDIIESCSCRIHOGANCRAAGVNEIDTEYMPIAHSROSALIMLOENOTWSRYICSCATTEEHVMAOLDUEAGTLIOONWOFA 45
CEPaxhGrpalaemomrbeiwtemreDrinicatsnacEdlhvaaSCrleagutteauhtpSoiydosnetoDefemsaiMgincrocavityHollowCathode 455570
GARSELNISNODIGWDLLUEEDEAIESDSLBCEIYHNMAMENRINAGCTNERODOSECATAMEVRPIMLTIEYNSHAOOTLILUOLTNOIWOOFNCCAOTPHPOEDRE 108
5SDSCIOEAMLTTUUELHTRTOIMADOINENNEAGORTLUEISSOOIWNMDUUDOELIFSTSIDCBIEHYSLACMERRIMGECEETRNEEOTMCMIAISVCSIRITOOYNSAHMOPLLLEOW 138
111113354499500
6SUMMARY,CONCLUSIONSANDFUTUREWORK...159
BIOGRAPHICALSKETCH
AobfRstetrqhauecitrUneoimfveeDnritsssistefyrotroatftihFoelnoDPreirgderaseeienntoePfdarDttoioacltthoFerulGofrfialdPluhmaietnletosSoocfphhtoyhoel
DSEISCMIAUGTNLHTAOANNDNDAEENODGOUELSSVOAEMMWLUPODLLIPTESIMSCEEHOLNAFETRMSOGEOFENLTAEUMTAMIINISOASCNLIRYOROSNECISASSIVYDOISUTFTEYESDMIHSOFCLORLREOTEW
By
CherylMorgan
August,1993
CMhaajiorrmaDnep:arPtrmoefn,t:JamCehsemDi.stWriynefordner
Thehollowcathodeglowdischargeisarathermodestatomicemission
source,but,nevertheless,hasmanydesirablecharacteristics.Thedischargeis
easytoinitiateandmaintain,providingsharpatomiclineswithalowbackground
continuum, Thelowpressureenvironmentvirtuallyeliminateschemical
reactions,matrixeffectsandself-absorption.Thenontherinalsputtering
atomizationprocessyieldsanatomcloudrepresentativeofthebulkmaterial.
Althoughtheoreticallythehollowcathodeglowdischargeisnearlyanideal
source,inrealityithassufferedfromweaksignaloutput.Ithasbeenshownthat
cathodegeometryplaysanimportantroleintheatomicemissionsignalintensity.
Thehollowcathodegeometryincreasestheemissionsensitivityovertheplanar
cathode,butnotenoughtorivalotheratomicemissionsources.Thework
presentedinthisdissertationfocusesontheuseofamicrocavityhollowcathode
glowdischarge(MCHCGD)asamethodtoenhancesignaloutput.
Althoughthereareseveraleffectivemultielementtechniquesinusetoday,
theyallrequirelargesamplevolumes.Therearecircumstances,however,in
whichonlyaverysmallsamplemaybeavailable(i.e.forensicsamplesand
preciousbodilyfluids)butthedeterminationofmanyelementsonthetraceand
uitratracelevelmayberequired.Thisprojectinvestigatestheapplicabilityof
MCHCGDtothesimultaneousmultielementanalysisofdiscretenanosamplesof
solutionresidues.
Severalimportantdiagnosticparametersweredetermined,including
pressure,voltage,current,sampledryingtime,slitwidthandchamberpurging.
phaseeTvhaeluaetxepdertihmeeMntCaHlCinGveDsteimgaitsisoinonwsaysstpeemrfaosramesdourincetfwoorupihtarsaetsr.aceTanhaelysfiirss.t
SingleelementanalysisofCuandPbwasperformedusingeachelement's
dsetrmoonngsetsrtaetmeidsstihaotntlhiene.MCTHheCGliDmitsisoafndeetxeccetliloenn,t2sopugrcfeorfoCruuiatnrdat3ra6cefganfaolrysPibs,.
ThesecondphaseevaluatedtheMCHCGDemissionsystemasamultielement
source.SimultaneousdeterminationofPb,V,andCrwasachieved,
demonstratingthattheMCHCGDisagoodmultielementsource.
INCTHRAOPDTUECRTIION
Theglowdischargeisarathermodestquasi-plasmawhichisgeneratedupon
sparkbreakdownbetweentwoelectrodesimmersedinalowpressure,raregas
environment.Itisaself-sustainingdischargeeasilymaintainableunderacertain
setofconditions-pressuresrangingfroml-10Torr,appliedvoltagesrangingfrom
400-2000Vandcurrentsrangingfrom1-1000mA,dependingontheraregas-
Inthislowpressureenvironment,theglowdischargeisvirtuallyfreefrom
self-absorptionandself-reversal.1Ityieldsnarrowspectrallines2andprovidesan
atomcloudrepresentativeofthebulkmaterialbeingsampled2withatomdensities
rangingfrom109-1016cm'2.4
Thegroundstatefreeatompopulation,necessaryforatomicemission
studies,isgeneratedbyanonthermal,nonselectivesputteringprocess.Because
thesputteringprocessisnon-thermal.manyoftheinterferencesassociatedwith
thermallyexcitedsources,suchasmatrixeffectsandsamplevaporization,arenot
associatedwiththed.c.glowdischarge.Thesubsequentexcitationofthefree
particlessputteredfromthesolidmatrixoccursasaresultoftheenergygenerated
inanelectricfield.Consequently,theglowdischargefallsintothecategoryof
electricdischarges.Thecategoriesofatomicemissionsourcesarepresentedin
Table1-1.
Table1-1.CategoriesofAtomicEmissionSources
ThermalSources:
HFilgahmeTsemperatureFurnaces
ElectricDischargeSources:
LowPressure
GlGPHeoloiawlsnlsaDolriewsrCcCahEatlatherhocgodterdesoedeless
AtmosphericPressure
HighVoltagea.c.Arcs
PlBRMaliFAPCCsIMocaalntmiwppardaDocaausnoismrcccmswioiitAacacittwtrhvviiracaHevveorsveeyngeDdseirsIsoncgdheuacnregdes