Direct analysis of neutrals using superconducting detector in tandem - - PDF document

Direct analysis of neutrals using superconducting detector in tandem mass spectrometry

TOD: Novel Developments in Mass Spectrometry Instrumentation: Analyzers, Detectors, Tandem Instruments! ASMS2009, Philadelphia!

City hall, May 31, 2009

Neutral loss in MS

• MS analyzes ions only.
• Ion reactions in MS/MS produce metastable molecules and

then ionic and neutral fragments.

[R. Cooks, ASMS2008 tutorial lecture, Metastable Ions: Past and Future in Mass Spectrometry]!

ABA + ABA + * ABA + *(< life time) AB+ +A AB +A + A + +B +A ...

• CAD!

ETD!

ABA + + N ABA *+ N+ ABA *(< life time) AB +A A +B +A AA +B

• ETD requires multiply-charged precursor ions so that at least
• ne of the fragments has a charge.
• Neutral products are lost, which is called “neutral loss.”

Re-ionization MS (indirect MS for neutral fragments)

• Ref. e.g. C. Wesdemiotis, F. McLafferty, Chem. Rev. 87, 485 (1987).
• S. Hayakawa, J. Mass Spectrom. 39, 111 (2004).!
• Neutralization re-ionization mass spectroscopy (NRMS)
• Charge inversion mass spectroscopy (CIMS)

in 1980s.

• Additional fragmentation during the re-ionization process

may take place.

• Efficiency of electron multiplier detectors depends on charge

states; quantitative analysis of reaction branches may be difficult.!

Heavy ion synchrotron storage ring (MeV, d > 10 m ) Dissociative recombination (DR) or Merged-beams experiments E

+ + +

A method of direct analysis for neutral fragments

• Ref. e.g.:
• R. Thomas, Mass Spectrom. Rev., 27, 485 (2008).
• A. Florescu-Mitchella, J. Mitchella, Phys. Rep. 430, 277 (2006).
• N. Adams, V. Poterya, and L. Babcock, Mass Spectrom. Rev. 25, 798 (2006).
• R. Phaneuf et al., Rep. Prog. Phys. 62, 1143 (1999).!

A u

• A

l

• S

i

• Kinetic energy sensitive

Si surface barrier detector

(100% detection efficiency, E = 20 keV)

~ cm

O n l y n e u t r a l

• p

r

• d

u c t s ( M e V )

• E2

E1 E3

E = E1 + E2 + E3

(with eV KER)

e – or ions

C4H+ DR experiment at ASTRID(Denmark)

• a. C4H+ + e C4H
• b. C3 + C
• c. C2 + C2
• d. C2 + C + C !

Au Al Si

C C2 C3 C4

Ref.

• G. Angelova et al., Int. J. Mass Spectrom. 232, 195 (2004).

~ cm

T

• K. Berkner et al., Proc. 7th Int. Conf. on Phys. of Electronic and Atomic Collisions, 422 (1971). !

Heavy-ion storage ring facilities

CRYRING (Stockholm), H. Danared et al., Proceedings of EPAC2006,Edinburgh!

FLAIR hall, GSI!

E Electrostatic sector Magnetic sector Cryostat (0.3 K) ion source (3 keV, EI) Ion deflector

3 m

Kinetic energy sensitive cryodetector (KEMS)

(E = 200 eV)

Our method, kinetic energy (KE) spectroscopy for neutrals in keV

+

E2 E1 E3 E3

+

Xe

+ !

E3

+ +

Collision chamber (CAD, ETD)

MS-I MS-II: E = E1 + E2 + E3

(with eV KER)

Single molecule hit for each pixel

Ref.

• M. Frank et al, Mass Spectrom. Rev. 18, 155 (1999).
• D. Koppenaal et al., Anal. Chem. 419A (2005).
• M. Ohkubo, Physica C 468, 1987 (2008).
• S. Shiki et al., J. Mass Spectrom. 43, 1686 (2008).
• S. Tomita et al., Appl. Phys. Lett. 91, 053507 (2007).
• K. Suzuki et al., Appl. Phys. Exp. 1, 031702 (2008).
• A. Casaburi et al., Appl. Phys. Lett. 94, 212502 (2009).

A cryodetector for neutrals as well as ions

Nb! Nb! Al Al

Si substrate!

1 nm AlOx 300 nm !! !!

"#$$%&'$()*#++%$,)!

• ./$/$0!

1! !!

• operates in a keV range.
• 100% detection efficiency

for both neutrals and ions

• 100 times better KE resolution!

fabricated at AIST!

Instruments for direct neutral analysis

CRYRING, Stockholm !

http://www.msi.se/MSL_files/Cryring.html!

3 m

MS/KEMS instrument, AIST, Tsukuba!

Circumference = 52 m! Observed physical phenomena are different, but the compact lab-based MS/MS instrument is unique; ions and neutrals without re-ionization. (The cryodetector is also useful for electrostatic storage rings at ~20 keV.)

Artificial peak

32%

(3 keV CH3CO+) without Xe target gas

SiO2(700 nm) 100 µm m/m= 14

Two modifications to eliminate the artificial peak 200 µm 1.bigger size to reduce the flame ratio

• 2. insertion of a phonon

converter layer into the SiO2 film

• M. Ohkubo et al., J Low Temp Phys 151, 760 (2008).!

Improved response

3 keV CH3CO+ without Xe target

MS/KEMS experiment

• 3 keV singly-charge precursor ions: acetyl and acetone

– (non QET molecules, dissociation from electronically excited state)

• Target gas: Xe 10-5 Pa ( < 20 % reduction of precursor flux)

– A high charge-exchange neutralization; CAD + ETD

• Precursor ions, neutralized precursor, ionic fragments,

neutral fragments were separated by the ion deflector and kinetic energies.

E = E1 + E2 + E3!

E2 E1 E3 E

CH3CO (CH3)2CO CO CH3

Reaction of acetyl (CH3CO)

• Life time of metastable CH3CO(A) = a few µs
• Neutral CO, CH3

+ : CH3 = 7 : 3

• CH3

+ (CAD), neutral CH3 (ETD)

Raw data Precursor subtracted

• CH3CO+(A) CH3

+ + CO(CAD)

70%

• CH3CO•(A) CH3• + CO(ETD)

30%

Molecule yield [counts /s]!

E = E1 + E2!

E1 E2 E

CH3CO CO + CH3!

E! E1! E2!

Reaction of acetone (CH3COCH3)

• Life time of metastable CH3CO(A) = ~ 100 s
• neutral CH3 and CO, CH3CO+ : CH3CO : CO = 7 : 1 : 2 !

Raw data Precursor subtracted

• (CH3)2CO +•(A) CH3CO+ + CH3• (CAD)

70%

• (CH3)2CO (A) CH3CO• + CH3• (ETD)

10%

• (CH3)2CO (A) CH3• + CH3• + CO (ETD)

20% E = E1 + E2 + E3!

E2 E1 E3 E

CH3CO (CH3)2CO CO CH3

Summary

• Lab-based MS/KEMS instrument for both ionic and neutral

fragments realized no “neutral loss”.

• Cryodetector has 100 times better KE resolution than Si

detector.

• Collision of acetyl and acetone with Xe leads to CAD and ETD.
• Branching ratios were directly determined even when only

neutral fragments are produced.

• In future,

– statistics and KE resolution must be improved (CH2, CH, C). – artificial peak must be eliminated completely. – coincidence experiment with array detector (KE and scattering angle). !

MS instruments equipped with cryodetectors, AIST

Double-focusing MS (EI/CI/FAB) MALDI TOF MS (100 channels)!

< 4,500 Da, < 3 keV < ~200k Da > 1 MDa, 20 keV

ESI TOF MS (100 channels) MALDI for sub-nano second response with mass-independent sensitivity !

> 1 MDa, 20 keV

Acknowledgement