A new mode of operation for the three-dimensional quadrupole ion store (QUISTOR): The selective ion reactor

In t&rnatior&dJournal of Mizss Spectkne 0 FZlsevier &ientific Publishing Company,

A NEW MODE QUADRUPOLE

OF-OPERATION ION STORE

fryand

Depnrtmenf

FOR

Cl+3

(QUISTOR):

““““““““T&DIMEEjSION&

y__TE&EF-IOti-. _: -_ _ ;-

and R-E_ MARCH

of Chemistty,

i& 7-c. <.-

10-n.Ph&&s;26 (i978). 155&162 Am&&k&~ l%i.nted in The~N&herladds

REACI-OR

J.E_ FULFORD

_:

-.

Trent Uniuersity,

:

Peterbokughi

(FLeceZved 20 July 1977)

.

:

: :-

-f---.. ;_ _.. _.

:

..-

tiniario~;-K9J

7B8 (Canada]

:

:-

ABSTRACT

;..

’

Faperimental verification is presented of a new mode of operation proposed recently for the QUTSTORquadrupole combination_ The new mode entails the application of the d-c. component of Go to the end-cap electrodes and the r.f_ component to the ring electrode. Spatial separation of the voltages combined with a pulsed d-c. potential permits operation of the ion storage so& in a rnz&s selective mode with relaxation to a total ion storage or total pressure mode_ When o-ted in this mode the QUISTOR may act as a specific ion reactor. INTFCODUCTION

-_

Recently,Bonner [1] hasproposedthe opkation ofathnxdimensional quadrupoleion store [2,3] in a mode with spat&alseparationoftherf_and d-c_ components of the electric field,&,. Intheusualmode ofoperation, wherein the end-caps are-earthed and &, .applied to theringelectrode,the potentialisgivenby

In the proposed mode ad.&_componentof'&, trodesyieldingthepotenfZalwhichjsgivenby.

isappliedtotheend&$elec-

-..

.-_

The potentialineqn_(Z),where&, hasbeenre$aced.by ~~~$%o&~,differs from that given.by eqn- (l),by the co&tar& factor~a~y~"%nner Cl] sciggested that, in the new mode,the QUISTORmay be_operatedasasimple device to determine ion-molecule reaction pathways, Since the d-c_ corn-. ponentmay-be applied asapulseitlnay~bepossibleto_~angebetweenmass spectiomefxic and total pressure modes permitting st&Gge of one __ionic5 > . -.

156

-at

-as

-0-T

Fig, l.Stability diagram forthe ~axis(a,q)= (O-15,038)-

three-dimensional

quadrupole.Notetheapexabovethe

species followed by relaxation to store all product ions; In this paper we present experimental evidence Tom two chemical systems, helium--air and helium=ethane, that this mode is operable, together with a discussion of some limitations of the technique_ The He’ ion was chosen for this study for two reasons: (i) a high reactivity in charg&xansfer processes and (ii) a low mass-tocharge ratio which was compatible with the electronic limitations of our apparatus [3]. The r-f. (Vi O-p) and d-c_ (U) voltages required to store He* selectively were calculated Tram the a and q coordinates for the apex of the appropriate stabilitydiagram,asshowninF’ig_l,where a,

=-

8eu mro2Ct2

With r. = XI-*

‘and

Qt=-

4f?v

mro2gp

m and operating at a Ikequency of l-6 MHz, V was calculafzd V.

as 892 V and U as -8.57

l=P-TAL

i _

_ -__

. ._..

_.;z:.-_. _____. .-

--

The d-c. p* train.asproposed by &x&i [l], (and shdwn in Fig:-&&: Was mod3ied in ordk_to_+&om&odat_e ~l~tipe:stqrage.and~~o~viil-. tages of-differingk&gnitudes_ This was &cm for two kasons~. (ij_'+avoid-inassdiscriminationresultingfrom-the vari+tionofion erkrgy upon entrance into the twodimensional quadrupole~analyser [4], and-&)- hi% .-Creation

-

(0)

--

Time

.._..

_^.

_

~. _.

_

.

r-l Creation

I

Repeller End-cap

-1

I

I _

Reaction

4 Attractor End-cap

Extraction

._

.-

t

7

Time

f

I w

-

Time

Sorting

Creation (bl.

I

-

Time

Time

5010.

._ _-

,

:

-..

Creation Repeller End-cap

.

I

-.

_

Reactiok

rime

: *..

Attractor End-cap

.: 4

. _ Fig.

Sorting

2, (a)

_

_

_._ __-: .

>-

Time

I The

d-c.

pe~@entIyadjustable

-

pulsetrahxfrom ref_ i_ @).The +&-action pulse.: _ ; __ -.

. _-_-

_:

: --. _-

Exfraction-

__..

-.

_, _;. ._.

.- -

.-

-_-. .Time

alterr+t.#ve__ds.

_ _._’:

_.

:-, _

‘.

PI+& &$&wit& i&l& _.__- .- __ z . ..-

158 INPUT

OUTPUT

MIXING

I

:

-

I

Y-L+70 v

-

r

trig

01 FGB

I

I

02 CDG

1

z .

trig

PGC

-7ue

-20v

03

LG All

diodes

All

resistors

IR

R170

07M.

l/&W.

5%.

1 il.

1

Fig_3_PuIsetraincircuitrpshowing

input,miaing and

output

stages.

extraction pulse of at least20 Visrequiredto emptythetrapcompletely for mass anaIysis whereas the selective storage oflowmass-tochargeratio ions may be effected with a d-c. component of less than 20 V.Thusthe pulse tram shown in Fig. 2(b)was implemented.The d.c.pulses were generated by three Hewlett-Packard 214A pulsegeneratorscoupledthroughthe circuit depicted in Pig. 3. Pulse generator A (PGA) provides the creation pulse,whilePGBandPGCprovidethesortingandextractionpulaes,re~pectrigtively. PGC and LG (ortec--Brookdeal Linear Gate Model9415)are WBrookdeaIScanDelay Generator gered simultaneously bytheSDG( Model9425).The SDG allows adjustmentofthereactiontime.Inthepulae mixing circuit,Fig. 3, diode Dlconductsthesortingsignaltotherepeller endcap,D2 passesthesortingsignalto attractorendcapand blocksthe passage cfthe extraction pulse to the repeller endcap;Dl,D2andtheload resistors main& exact load.ing conditions required to achieve accurate duplication of the sorting pulses to the endcaps.Theloading effect produces a ca. 20% reduction in input amplitude to the endcaps.Thewave. .ttedlundistortedasshowninFig_2(b).Thechoiceofload formsweretr resistancewascriti~inorderto prese.rv etheintegri*ofthewav*forms.

Fig. 4~Spech-a ofH_ mixture (100rl). (a)Continuousionization (b) 4OOpsstorage (no ds.on end-caps);(c)400ps ofsortingand zeq reactiontime;(d)40O__pso$.so+~.1g and2msreactiontime_ _- ;:._:.._ .’ ., -_. : . _ .. . PrekCinary chaiacterization was ‘carried out -at a presske --ofca;-1.3 X lo-* Paandwi~-anionizationenergyofca_70eV. --. .-. -I: RESULTS

Thecontin~o~usionization spe@trum (i.el:with no sorting-pulse) is'shown F&-4(a); The electron bean-was-then -puked as in-the-u&al:-tiodelofoperation tdgive the 400+s~&or@e~specizuk of Fig24(b)l.Applicationdfa sorting p&,-400-~-+1 dU.r&io~v&b zero reactiontime; folIotiedb~~taui~ ing-0fttie.r.f. and-d.c.-Supplies,yielded-~the'-selectivestoPages~trum-shown in-Fig.4(c),'SelecSve-stor@+wasconEr+i -when-the sorting:p%.kdis._.:_-__._-, : con$inuedandthespectrumofFig_4(b)wasre&o~,On& the~se@ASv& storage'ofHe~hadbeen_a~~~~d~g400Irs6fsort-. ing,the.m~ective-ljddde~~~~'to.t~~~'~~e-rnod_eto.allow_ in

.-

160‘

16

Fig_ 5_ SpectraofHe mixture(l:l)(a)fZontinuous ionization;@)600j~ofsorting andzeroreactiontime;(c)600psofsortingand200psreactiontime.

2ms ofreactiontimeciuring whichtheproductsofiom okculereactions were accumulated_ At the end of this period all the ions were ejected for mass analysis_ In Fig. 4(d) is illuskated a spectrum of the H& mixture obtainedinthismanner_TheHe-C~ systemyieldedsimilarresultswhich are shown in Fig, 5(a)-(c), These figures clearly demonstrate &he formation,bychargeexchangewithHe', of Nf andC= and CH$,respectively_ DISCU!SSION The relatively poor sensitivityof this mode probably originates in the instabilityoftheagedd_c_pulsegen~~rsusedwhicharestabletoca_4% only.Foranalytical massspectromeky,typicallyquotedpowersupplystabilitiesare in the range of 1 part in lo4 [5-J_This stringent requirement is readily understood fiom examination oftheoperatingpointonastabili~ diagram;siightinstabilities in the d.c.potential can drastically alterthe resolution. InFig_6tiisseenthattotalionstorageattherf_voltagecorrespon&ng to& selectionshouldstzMlizeall massesgreat4TthanM,.Ekpen'm@&y,

Fig. 6. Partial stability

diagrams of various masses in

V’i?JSPaCe.

the ion storage efficiencyunder the conditions of the '?owq tail"of the stabilitydiagram isdimini.ched_Thusthere~lbeaneffectiveuppermass limit. AU masses less than Ml

will not be stored. Thus it would seem that

mechanistic studiesmightbestbecarriedoutwithreacta.ntandproductions of similnr m/e value, The mass range of the new mode is limited at present by the rkgnitude of

d.c_ pukes .(+-lo0V) commercially available,Relativelyadvanced rf. circuitryis readilyavailable, For example, at l-67 MHz with r. =10w2 m,the d.c_puIseamplitude imposesalimitof m/e 46forthehighestsekctableion. Reduction of a err, couldincreasethemassrange,howevenrthesemeasures. ateknowntoresultiapoorersensi~~becausefewerionsarestored[6,7]. ACKNOWLEDGEMENTS

We

wish to acknowledge

with thanks the Enancial support of Trent Council of Canada and Province of Ontario graduate fellowships (1976-1978) to J_EL Fulford. We are also indeb~to~_GD.W~andDr.R.F.Bonnerforhe~pfuldiscussions_ Utiversity,

the

National

Research

REFERENCES R-F_ Banner, Int. J. Mass Spectrom. Ion Phys., 23 (1977) 249, G. Lawson, J-F-J. Todd and R-F_ Banner. in D_ Price and J-FL Todd (Eds;), “Theoretical and Experimental Studies with the Quadrupole Ion Storage Trap (QUISTOR)‘, Dynamic Mass Spectrometry, VoL 4, Heyden and Son, London, 1976, Cb. 4, R.F. Banner, R&Mar&and J.Ihuup,Int,J.Mass Speetrom-Ion Wys; 22 (1976) 17. WE, Austin, AE_ HoIme and J-H_ Leek, io P-H. Dawson (Ed-), QuadruPole Mass SFtrometry, Ch. VI, EIsevier. New York. 1976, p- 142-

.

162

5 WJL

Austin,

J.H_ Leek, in P-N_ Dawson (Ed-), Quadrupole Mass Spec1976, p_ 146. 6 PH_ Dawn and N-R_ Whetten, Fii Report, Contract No. Fl9628~8C-0261, General Hectric Company, 1969, p_ 12_ 7 JJ?_J_ Todd, G. Lawson and R_F_ Banner, in P-H_ Dawson (Ed_), Quadrupole Mass Spectrometry, Ch. XIII, Efsevier, New York, 1976, p_ 215. trometry,

AX_

EIsevier,

HoIn&and New

York,