TandemMassSpectrometryonaMiniaturizedLaserDesorptionTime-of-FlightMassSpectrometer

XiangLiUniversityofMaryland,

BaltimoreCountyBaltimore,MD21250

301-614-6016xiang.li@nasa.gov

Timothy Cornish, ScottEcelbergerC&EResearch,Inc.

Catonsville,MD21228301-614-6016

tcornish@CEResearchInc.comSAE@CEResearchInc.com

StephanieA.Getty,WilliamB.Brinckerhoff

NASAGoddardSpaceFlightCenter

Greenbelt,MD20771301-614-6397

stephanie.a.getty@nasa.govAbstract— Tandem mass spectrometry (MS/MS) is a powerfulandwidely-usedtechniqueforidentifyingthemolecularstructureof organic constituents of a complex sample. Application ofMS/MStothestudyofunknownplanetarysamplesonaremotespace mission would contribute to our understanding of theorigin, evolution, and distribution of extraterrestrial organics inoursolarsystem.HerewereportontherealizationofMS/MSonaminiaturizedlaserdesorptiontime-of-flightmassspectrometer(LD-TOF-MS), which is one of the most promising instrumenttypes for future planetarymissions. This achievement relies ontwo critical components: a curved-field reflectronandapulsed-piniongate.Theseenableuseofthecomplementarypost-sourcedecay (PSD) and laser-assisted collision induced dissociation (L-CID)MS/MSmethodsondiversemeasurementtargetswithonlymodest investment in instrumentresourcessuchasvolumeandweight.MS/MS spectra of selectedmolecular targets in variousorganic standards exhibit excellent agreement when comparedwithresultsfromacommercial,laboratory-scaleTOFinstrument,demonstrating thepotentialof thispowerful technique inspaceandplanetaryenvironments.

IndexTerms—laserdesorptiontime-of-flightmassspectrometer(LD-TOF-MS), laser desorption mass spectrometry (LDMS),tandem mass spectrometry (MS/MS), post-source decay (PSD),laser-assistedcollisioninduceddissociation(L-CID)

TABLEOFCONTENTS1.INTRODUCTION...........................................12.INSTRUMENTDESIGN........................................23.EXPERIMENTALMETHODS......................34. RESULTS..........................................................45. DISCUSSION...................................................56.CONCLUSIONS.............................................6REFERENCES....................................................7

BIOGRAPHY......................................................7

1.INTRODUCTIONMass spectrometers (MS)havebeenemployedonanumberof space missions to measure the atomic, molecular, andwilliam.b.brinckerhoff@nasa.gov

isotopiccompositionof remoteplanetaryenvironments (1).Suchstudieshave informedourunderstandingoftheoriginandevolutionofoursolarsystem,theoriginoflifeonEarth,and the potential for life elsewhere. Many of the targetsprioritizedforfutureplanetaryexploration,suchascomets,asteroids,andplanetarysatellites,arecharacterizedbygreatchemical complexity, requiring advances in remotemolecularanalysistechnique.Intandemmassspectrometry(also called MS/MS, for “mass spectrometry/massspectrometry”),aparticular ionor rangeof ions is selectedfromaninitialmassspectrum,isolatedbyremovingallotherspeciesfromfurtheranalysis,andsubsequentlyfragmented(most commonly through collisionswith gas). The resultingfragmentationpatternisthusassociatedexclusivelywiththeoriginal ion/s, enabling high-confidence identification andstructural analysis. MS/MS is compatible with a variety ofmassanalyzersused inspace flight.Forexample, the linearion trap mass spectrometer in theMars Organic MoleculeAnalyzer (MOMA)on theExoMars rover (2,3)usesMS/MSto isolate and fragment molecular ions of interest, toaddressmissionrequirementstodetectpotentialmolecularbiosignaturesinMarssurfaceandsubsurfacematerials.

The laser desorption time-of-flight mass spectrometer (LD-TOF-MS)iswidelyemployedinanalyticallaboratoriesduetoits straightforward operation, high-mass detection, highsensitivity,andrapidanalysistimes.Whilesuchinstrumentsare large, often containing ion flight tubes over onemeterlong tomaximize resolution, LD-TOF-MS is particularlywellsuited tominiaturization and remote application due to itslightweight design, simple electronics (e.g., no RF powersupplies are required), and direct compatibilitywith airlessenvironments.Inpreviouswork,wehavedemonstratedthepowerfulanalyticalcapabilitiesofacompactLD-TOF-MSforspace missions (4). Adapting the MS/MS capability to aminiaturized TOF mass spectrometer has requireddevelopment of specialized approaches beyond thoseemployed on commercial instrumentation. For example,MS/MS on the Bruker Autoflex Speed MALDI TOF/TOF (5)employs a separate high-voltage “LIFT” collision cell tofragment and reaccelerate product ions. This approachwouldadd substantialweight/volume,power consumption,andadditionalmechanismstoaminiatureinstrument.Inthisstudy,wedescribeourMS/MSapproach,whichcombinesacurvedfieldreflectronandapulsedpinion

https://ntrs.nasa.gov/search.jsp?R=20170003157 2020-07-12T01:58:03+00:00Z

gating technique. Fragmentation is accomplished byspontaneous (passive) post-source decay (PSD) or by laser-induced (active) collision induced dissociation (L-CID). In thissetup, minimal additional weight/volume is required. Theusualexternalsupplyofcollisiongasisnotneeded,renderingthe instrument far more suitable for space missions. Todemonstrate the performance of this approach, theMS/MSspectra of selected peaks in various space-relevant organicstandardsweremeasuredand compared to commercial TOFinstrumentresults.

2.INSTRUMENTDESIGN2.1TandemMassSpectrometry(MS/MS)TheminiaturizedLD-TOF-MShasbeenpreviouslyreported(4).Briefly, the instrumentprototypeuses lowvoltages (<5 kV),measures less than 30 cm long, and weighs ~5 kg includinglaser and all electronics (4). A key component of the massspectrometeristhecylindrical,gridlesscurved-fieldreflectron(CFR)thathasbeendescribedelsewhere(6,7).Theenhancedinstrument also features a pulsed pin ion gate to isolate atargeted ion peak at a specific time. Both features aredescribedbelow. In the simplest LD-TOF-MSconfiguration, asingleUVlaser(355nmfromaNd:YAGlaser,or337nmfroma N2 laser) is focused onto the surface of a solid sample togenerate both positive and negative ions within a fewnanosecond pulsewidth. The simplemass analyzer providesunit mass resolution at several hundred Da (4). To achievecollisioninduceddissociation(CID)inMS/MSmode,asecondlaserbeam isdirectedontoasolidsurfacealong thepathofdrifting ion beam, creating a highly-localized plume ofneutrals and ions to collidewith (and thereby fragment) theionsofinterest.The Curved Field Reflectron (CFR): The curvature of the

potential gradient in the CFR is used to focus ions ofwidelyvarying kinetic energies entering the reflector. To illustratetheversatilityofitsoperation,considertwotypesoffragmentions.Stable(prompt)fragmentionsformedattheionsourceacquire the full translational energy of source voltage,penetratethefulldepthofthereflector,andarebroughtintofocus at the detector surface. This is the basic operationalprinciple of a standard reflectron TOF-MS. In comparison,productionsformedsubsequenttotheirexitfromthesource(so called post source decay (PSD) ions), have reducedtranslational energy due to their loss of mass during thefragmentation process in the field-free drift region. Hencethese ionspenetrate less into the reflectronandwould thusarrive at the detector entirely unfocused in a conventionallineargradientreflectron.IntheCFRanalyzer,however,thesereducedenergy ionsare focusedat the samedetectorplaneas the full energy ions formed in the ion source (Figure 1).Where traditional TOF reflector analyzers are capable ofresolving stable fragmented ions, the CFR analyzer focusesbothstableandPSDionssimultaneously.ThiscapabilityaddssignificantbenefitinMS/MSanalysismodewhereboth

precursor and PSD ions can be detected simultaneously.Whilethisfeaturehasmajorimplicationsforrecoveringand

deconvolutionofPSDproductionspectra,thechallengeistoisolate and identify these product ions and formulate aprecisecalibrationscalesothatthis isapowerfulanalyticalfeature rather thanone thatmerely complicates the stableionspectrum.

Figure1.Comparisonofthefocusingpropertiesbetweenthe(a)standardlinearreflectorandthe(b)curved-fieldreflector.The focal points of the product ions are widely separatedfrom each other in the case of linear reflector while theycoalescetoasinglepointinthecaseof

Figure 2. (Top) The detailed wire fame reflector andintegrateddetectorbody. (Bottom)Detailof thepulsed-piniongate.

Pulsed-Pin Ion gate: Ion gates

have been used for decades to separate ion clusters in a

beam. This is a particularly useful device to develop thetandemTOF-MS.Inourcase,thegateconsistsofasinglethinwire that extends between two grids held at the driftpotential(Figure2).Thewireispulsedto1.5kVrelativetothedrift potential inorder todeflect those ionspassing throughthe gate region so that they are suppressed fromdetection.Ionsof interestpassthroughthegateonlyduringtheperiodinwhichthewireisreturnedtothedriftpotential.Post Source Decay (PSD): A highly fortuitous property of

product ion formation in a TOF mass analyzer is that PSDproducts, formed within the drift region, travel in a clusteralong with the ions from which they are formed (precursorions) at the same velocity and pass through the ion gate atpreciselythesametime.Therefore,ifthegateispulsed“low”(off)toallowaparticulartargetedmassthrough(ataspecifictime), both precursor and product ions associatedwith thatprecursor pass through together, while all other ions areeliminatedfromthatspectrumusingthedeflectionpropertiesof the gate. As mentioned earlier, the PSD ions would bedetected along with parent ions by the CFR mass analyzer,therefore formingaMS/MSspectrum.DetectionofPSD ionshasbeenfoundtobeveryusefulinbiochemicalidentification,particularly for the sequencing information it contributes inpeptideanalyses.Laser-Assisted Collision Induced Dissociation (L-CID):

TraditionalCIDemploysaneutralcollisiongas(suchasheliumorargon)topromotedissociationthroughdirectcollisionsoftheinjectedgaswiththeionbeam.Highlylimitedgasstorage,regulation, pumping capabilities in flight instruments rendergas cell CID an less-desirable option in ourminiaturized LD-TOF-MS.Wethereforedeviseda relativelysimplemethodtoimplementtheMS/MSfeaturebyaddingasecondlaserbeampreciselysynchronizedtothemaindesorption/ionizationlaserpulsetodeliverashortburstofcollisiongas intothepathofthe ion beam (Laser-Assisted CID). Since the gas plumegenerationandexpansion isveryslowcomparedtothetimescaleofionbeampassage,nobettertimingcontrolotherthansynchronizing the two lasers is needed, i.e., all the ionsgeneratedfromtheionsourcewouldpassthroughtheplumeforcollisionstooccur.Usingthismethod,negligibleadditionalpressure is generated by the L-CID process, therebyeliminating the need for increased pumping capability.Comparedtothe iontrap’s low-energycollisionprocesses,L-CID in the TOF-MS ion flight path are high-energy events(>5000V),afeaturethatisoftenfavorableforuniqueproductidentification. We expect to measure most MS/MS spectrathroughgatingandPSDdetection,butL-CIDwouldaddvaluefor specific target compounds that require higher collision

energyforuniqueMS/MScharacterization.2.2BenefitsofMS/MSIn MS/MS, individual molecular species can be separatedfrom a complex background, allowing for detection and

assignment of its product ions. Additionally, when lowermassmatrixorsalt ionsareejectedfromtheionbeam,theionsof interest (whichpass unperturbed through the gate)canbedetectedwithgreatersensitivityandaccuracyduetotheeliminationofmicrochannelplate(MCP)detectordead-timeeffects.OnceaMCPchannelisusedtodetectanion,itrequiresabout1msforthatchanneltorechargeinordertodetect another ion, which is much longer than the totalspectrum acquisition time. Moreover, since precursor andproduct ions pass through the gate simultaneously, it isfoundtobeunnecessaryfortheparentiontobedetectedinaproductionspectrum.Thatis,ifthegateistunedtoallowpassage of ions at a specified predetermined time, acharacteristic product ion spectrum will identify thepresenceof themolecular species in the sample regardlessof the fact that the intact molecular ion may remainundetected. This is a highly beneficial feature of tandemmass spectrometry in detecting those species that are notsufficiently stable to remain intact throughout the passagethroughthemassanalyzer.ImportantanalyteswithreducedstabilitywouldnotbeobservedinconventionalMSanalysisbutwouldbedetectedthroughitsproductionspectruminatandeminstrument.

Figure 3. Schematic of Laser-assisted Collision InducedDissociation(L-CID)setupintheLD-TOF-MSinstrument.

3.EXPERIMENTALMETHODSIn this study, we present MS/MS spectra of severalrepresentativesamples,includingD-cyano-4-hydroxycinnamic acid (CHCA), tributylphosphate (TBP),the amino acid valine, two dipeptides (glycine-glycine andaspartame), and rhodamine 6G (R6G). CHCA itself is acommonlyusedMatrixAssistedLaserDesorption/Ionization(MALDI) matrix compound, and in the cases of valine,glycine-glycine, aspartame, and tributylphosphate samples,CHCAwere deposited first on the sample stubs before thesamplewasdepositedontopprovidingtheMALDIeffect intheiongeneration.CHCAwassolvatedin50:50(0.1%TFAin

water):acetonitrile (v/v), andsampleswereeitherdissolved

orformedintoaslurryinthesamesolution.R6Ginmethanolwasdroppeddirectlyon the sample stubwithoutmatrix.Allsamplesweredried in air, then transferred into the TOF-MSforpump-downprior tomeasurement.Todesorband ionizethesample,theUVlaserenergywasvariedfrom40to140μJ,correspondingtoarangeofpeakpowerdensitybetween77and 450 MW/cm2. For the L-CID mode, a second nitrogen

laser (337 nm) was used to ablate a graphite surfacegeneratingalocalneutralplumetocollidewiththeionbeam.Spectra can be obtained in both positive and negative ionmodes,butwefocusedonthepositivemodeinthisstudy.

To evaluate the performance of the prototype massspectrometer, we also analyzed the same suite of samplesutilizingacommercialMALDITOFmassspectrometer(BrukerAutoflexSpeed).Inthisinstrument,sampleswereintroducedinto the instrument on a stainless steel plate with ~2 uLsamplesolutionorslurriesdriedinairbeforetransferringintothe high vacuum environment. The ion source of thecommercial instrument isequippedwithaNd:YAGlaser(355nm, <5 ns pulse) focused to an elliptical spot withapproximatedimensionsof0.2×0.2mm.WhenoperatinginMS/MS mode, choices between PSD mode and CID (usingargon) modes can be made, and in many cases the resultsshowednegligibledifferencebetweenthetwomodes.

4.RESULTSMass spectral data from each sample were comparedbetween the miniaturized LD-TOF-MS and the commercialBrukerMALDITOF-MS.CHCA: The full mass spectrum of CHCA and the MS/MS

spectrumoftheselectedpeak,protonateddimerofCHCA,atm/z379areshown inFigure4.The full spectrumofCHCA isshownhere todemonstrate that thepingatecaneffectivelyselect the target ion and thePSD ions alongwith it. The iongatingworkssimilarlyforallthesamplestestedhere,soonlyMS/MS spectra for other samples are shown. Whencomparing theMS/MSspectrumofCHCAdimerobtainedontheminiaturized TOF-MS to the corresponding spectrum ontheBrukercommercial instrument, it isclear that theresultsareconsistentwitheachother. Thetwomajor fragmentsofthe CHCA dimer can be assigned as the protonated CHCAmonomer and themonomerwith the loss of an -OH group.Note that the CID operational mode on the commercialinstrumentdidnot enhance theproduct ion signal observedinthePSDspectrum.TBP: Tributylphosphate isusedasa solvent forextraction

and purification of rare earth metals from their ores. Thiscompoundhasthreesidechainsboundtoacentralphosphategroup.TheMS/MSspectrumoftheselectedpeak,protonatedmonomer of TBP (m/z 267), is compared between theminiatureLD-TOF-MSandcommercialinstrument(Figure5).Theresultsonbothinstrumentsareconsistentshowing

Figure4.(TOP)FullmassspectrumofCHCA.(MIDDLE)MS/MSspectrumofm/z379peakmeasuredontheminiatureLD-TOF-MS.(BOTTOM)TheMS/MSspectrumofthesamepeakmeasuredonthecommercialBrukerMALDITOFmassspectrometer.Clearlyobservedisthesamepatternofproductionpeaks(highlighted).

Figure5. (TOP)MS/MS spectrumof protonatedparentTBP

ion, m/z 267 measured on miniaturized LD-TOF-MS.(

BOTTOM) MS/MS spectrum of the same peak measured ontheBrukerMALDITOF-MS.Asimilarpatternofthe

fragment

peakswereobserved(highlighted).

threeequallyspacedpeaksineachspectrumcorrespondingtothe consecutive losses of the side chains. Again, the PSDspectrumisfoundtobenearlyidenticaltotheCIDproductionspectrum.ine:Amongthe20biologicalaminoacids,valineisone that is also found in meteorites, and is thus a targetmolecules for studies of pre-biotic processes in the solarsystem. The MS/MS spectra of the gate-selected peak,protonated monomer of valine (m/z 118) measured byminiaturized TOF-MS and the commercial instrument areshowninFigure6.Theresultsonboth instrumentsarequiteconsistent. Themajor fragmentpeak canbe assigned as thelossofthe-COOHgroup.Dipeptides:Twodipeptides,glycine-glycineandaspartame,

werealsocomparedinthetwomassspectrometers.Glycine-glycine is the simplest peptide, and is useful as a buffer formanybiological systems.Aspartame is amethyl ester of theaspartic acid-phenylalanine dipeptide that is used as anartificialsweetener.TheMS/MSspectraofselectedpeaksareshown (Figs. 7 and 8). Here, the protonated monomer ofglycine-glycine (m/z 133), and protonated monomer ofaspartame (m/z 295), were selected and measured. Theresultsonbothinstrumentsareconsistentforeachdipeptide.Major fragmentpeaks canbeassignedas the lossof variousfunctionalgroups.

Figure6.(TOP)MS/MSspectrumofprotonatedvaline(m/z

118) measured on miniaturized LD-TOF-MS. (BOTTOM)

MS/MS spectrum of the same peak measured on the

commercialBrukerMALDITOFmassspectrometer.Thesame

patternoffragmentationpeaks

wereobserved.

Rhodamine6G:Rhodamine6Gisahighlyfluorescentdye.In

our current LD-TOF-MSexperiment, rhodamine6Gwasusedto demonstrate L-CIDperformance. TheMS/MS spectrumofthemainpeakoftherhodamine6Gspectrum(m/z=433),wasmeasuredunderbothPSDandL-CIDmodes(Figure8).InPSDmode,therewereseveralfragmentpeaksobserved,butwhenused in the L-CID mode, a series of fragment ions at lowermassareobservedindicatingcollisionswiththedesorbedgasprovidessufficientenergyfortheparentiontofragmentintosmaller species. Compared to data acquired on thecommercial instrument (Figure 9), the same results wereobservedwhen a traditional CID gas (argon)was used. ThisprovidesevidencethatL-CIDandtraditionalCIDexhibitsimilarcollisionenergiesanddetectionefficiencies.

Figure7.(TOP)TheMS/MSspectrumofprotonated

parent

glycine-glycineion(m/z=133)measuredontheminiaturized

TOF-MS.(BOTTOM)TheMS/MSspectrumofthesamepeak

measured on the commercial BrukerMALDI TOF mass

spectrometer.

Figure8. (TOP)TheMS/MSspectrumofprotonatedparentaspartame ion, (m/z=295) measured on miniaturized TOF-MS. (BOTTOM)The MS/MS spectrum of the same peakmeasured on the commercial Bruker MALDI TOF massspectrometer.

5.DISCUSSIONWe demonstrated here the capability of performing tandemmass spectrometry on a miniaturized TOF-MS. It isnoteworthy that systematic acquisition of PSD product iondata yields MS/MS spectra without adding any significantweight or volume to the instrument. Furthermore, it isremarkable that formanysamplesof interest,PSDefficiencyisashighasthatforCID(andthiswasfoundtrueevenonthecommercial instrument). In a real-world sample analysisscenario, most of the MS/MS measurements would requireonlyPSD,whileonlyspecificcompoundsrequireL-CID.

TheLDItechniqueadvancestheabilitytodesorbionsdirectlyfromasamplesubstratetodetectarangeofnonvolatileandgenerallyhighmolecularweightorganics,aswellaselementalabundances in complex samples. Coupling LDI to a highly-compact tandem TOF-MS then realizes a versatile tool formissionstoexploreMars,Titan,themoonsofJupiter,Saturn

and airless bodies (comets, asteroids and the Moon).Additionally, the MS/MS technique brings the extremelyimportantmolecular structure analysis capability to bear onindividual organic molecules, a key step on the NASARoadmap,whichseekstounderstandtheoriginandhistoryofthe Solar System and the potential for life elsewhere.Carefully-planned MS/MS application to complex unknownscanhelp resolve thehundreds (ormore)possiblecandidatesfor a givenmasspeak, particularywhenexaminingpotentialmolecularbiosignaturesforwhichthedetailedstructure(e.g.,sidegroups)aremosttellingoffunction.

6.OUTLOOKThe miniaturized LD-TOF-MS, including MS/MS capability,offers a rapid, low cost, portable technology for thedetection and structural analysis of semi-volatile and non-volatile microorganisms, organics, trace metals, elementalabundances as well as in Earth-bound applications such asdetection of explosives and food pathogens. To furtherimprove the instrument, we will study the MS/MSmeasurementmoreinthenegativeionmode.Althoughtheinstrument is capable of rapidly switching betweensymmetricdetectionofionswitheitherpositiveornegativepolarities,theefficiencyofthenegativeionsPSDcomparetopositive ions is not well-characterized at this point.Furthermore,an importantnextgoalwillbetodevelopthefull tandem LD-TOF-MS at flight scale to a technologyreadiness level (TRL) from its current level of 5 up to 6,indicating compliance with the launch, spaceflight, andoperational environments and readiness for flightdevelopment.

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BIOGRAPHY

Xiang Li received his B.S. in Chemistryfrom the Peking University, China in2003, and Ph.D. in Physical Chemistryfrom the Johns Hopkins University in2009. He is an assistant research

Figure 9. (LEFT) TheMS/MS spectrumof rhodamine 6G,m=443,measured onminiaturized TOF-MSwith PSD and L-CID.(RIGHT)TheMS/MSspectrumofrhodamine6G,m=443,measuredonthecommercialTOFmassspectrometerwithPSDandCID.Samepatternofthefragmentpeakswereobserved.

scientist with a joint appointment at the University ofMaryland,BaltimoreCountyandNASAGoddardSpaceFlight

Center.Hisresearchfocusesonthedetection of trace element and astrobiologically relevantorganic molecules in planetary systems, like Mars. He isespecially interested in the instrumentdevelopmentof time-of-flight and ion trap mass spectrometers with variousionizationandiongatingtechniques.Heservesasmassspec.scientistfortheMOMAiontrapMSonExoMarsandCo-IondevelopmentofLITMSandMACROSinstrument.

TimothyCornishPh.D.,PresidentofC&EResearch, Inc. in Columbia, MD, ascientific consulting and CRADcompanyspecializinginminiatureTimeOf Flight Mass Spectrometry fromconceptual design to prototype development and testing. He hasextensiveexperienceinhighresolution

optical spectroscopy and laser applications for chemicalanalysis. His recent efforts have focused onminiaturemassspectrometry with targeted developments directed towardboth mineralogical and biomarker analysis on landedplanetary missions, as well as development of a highperformance tandem mass spectrometry for field-portableterrestrialapplications.

ScottEcelbergerisVicePresidentandco-founderofC&EResearch,Inc.inColumbiaMD.HehasanM.S.inAppliedPhysicsfromtheJohnsHopkinsUniversityandaB.S.inPhysicsfromPennState.Scottisahands-onexperimental physicistwho designs,builds, and tests analyticalinstrumentation.He

hasbroadexperiencewithvacuumsystems,lasersandoptics,highspeedandhighvoltageelectronics,BSL-3containmentlabs,vacuumdepositionsystems,semiconductorcharacterization,andTOFMassSpectrometry.CurrentprojectsincludeminiatureTOFmassspectrometryformineralogyandbio-defenseandsingleparticlemassspecinstrumentationforaerosolanalysis.

StephanieGettyisaResearchPlanetary

ScientistinthePlanetaryEnvironmentsLaboratoryatNASA’sGoddardSpaceFlightCenterwithinterestsinthedevelopment of advancedinstrumentationforthecompositionalanalysisofplanetaryenvironments.She

currentlyserves as PrincipalInvestigator ofthePIDD-fundeddevelopmentofatwo-steplasertandemtime-of-flightmassspectrometerfortargetedelucidationoforganicsinnon-volatileplanetarysurfacechemistry.ShealsoservesasPrincipalInvestigatoroftheASTID-fundeddevelopmentofOASIS,aliquidchromatography-massspectrometerforinsituanalysisofprebioticcompounds.SheisamemberoftheExoMarsMOMA-MSteamandaMarsScienceLaboratoryCollaborator.

William Brinckerhoff is a senior spaceresearch associate at NASA’s GoddardSpace Flight Center. He received his Ph.D.in Physics from the Ohio State University.His current research interests includedevelopment of novel miniature massspectrometers and sample handlingsystemsforplanetarymissions,synthesisof

organic compounds in the interstellar medium, and thehabitability of Mars. He serves as a Co-I on MSL/SAM andprojectscientistfortheMOMAiontrapMSonExoMars.