Thermo Scientific™ Project Vienna Towards Neoma™ MC ...

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Markus Pfeifer1,*, Grant Craig1, Henning Wehrs1, Tim Elliott2, Johannes Schwieters1

Project Vienna

Prospects for a novel pre-cell

mass filter for MC-ICP-MS/MS

1 Thermo Fisher Scientific, Bremen, Germany2 Bristol Isotope Group, University of Bristol, UK

* Specialist Product Evaluation

Email: [email protected]

Introduction - Thermo Scientific™ Proteus™ MC-ICP-MS/MS

• First prototype in collaboration with University of Bristol

(2015)

• A one-off tribrid instrument.

• Q1 retained before the collision/reaction cell, this pre-

cell mass filter can control which masses enter the cell.

• Proteus has advantages compared to other instruments as it can be fully employed as an MC-ICP-

MS/MS

• Double focusing

• Pre-cell mass filter

• High resolution

• Although a considerable success, there are two disadvantages

• Lower sensitivity due to the lower energy extraction of ions from the plasma

• Non-exponential mass bias imprinted on the transmitted ions by the quadrupole

• Building upon these experiences, project Vienna, was started to produce a new prototype CRC-MC-

ICP-MS/MS

Introduction – Lessons learned

Introducing Thermo Scientific™ Vienna MC-ICP-MS/MS

• Prototype module based on Thermo Scientific™

Neptune XT™ MC-ICP-MS/MS in Bremen

• Full established MC-ICP-MS functionality

• High energy extraction

• High energy pre-cell mass filter

• Exponential mass bias

• Hexapole collision/reaction cell

• Two modes of operation.

• MS/MS functionality with reactive gases (O2, NH3, SF6)

• Collision gases (H2, He)

• An E-field is applied against a B-field such that the mass in the center of the desired window is transmitted

straight through the filter. All other masses diverge away from the central line of transmission.

• A slit is then used to cut the window of transmitted masses.

• A second set of B-field and E-fields of equal strengths are then used to bring all the masses in the window back

onto the central line of transmission before passing into the collision/reaction cell.

Introduction – How the pre-cell mass filter works

Baffles

CRC

ICPMC-MS

Selectable Slit

E

N

S

E

Acceleration

Lens

Deceleration

LensN

S

Inversion

Lens

• As the pre-cell mass filter consists of static E- and B fields, the Neptune XT specifications were retained.

• Pre-cell mass filter set for broad transmission, no collision/reaction gas.

• The pre-cell mass filter can be tuned to select a “window” of masses which are transmitted into the

collision/reaction cell.

• Important: removal of 40Ar+, 40Ar16O+ and 40Ar40Ar+ beams.

• Without these large ion beams in the mass spectrometer space charge effects are greatly reduced.

• Removal of Ar species and further ions greatly reduces secondary reactions in collision/reaction cell.

• Clear improvement in sensitivity compared to Neptune XT.

• Dramatic improvement in abundance sensitivity compared to Neptune XT.

Introduction – Advantages of pre-cell mass filter design

Operation Mode 1 – Standard collision scheme

CRC

Multicollector

Full mass spectrum from

ICP, sample ions plus Ar

plasma species.

Vienna set to full

transmission, large mass

window

He and H2 gas is added to

the cell to neutralise plasma

species by charge transfer

e.g. Ar+ + H2 → Ar + H2+.

Isotope measurements are

made on analyte ions free

from interfering Ar plasma

species.

He + H2 gas

• Simple operation mode.

• Vienna in full transmission, minor use of pre-cell mass

filter.

• He and H2 in cell for energy/charge transfer and

collisional fragmentation of Ar and Ar based polyatomic

ions.

• Ca, K

• 150 ppb K in 2% HNO3

• X-skimmer & Jet-sampler cones

• ESI Apex Omega Q

• Successful removal of 40Ar1H

• H2 – 8 mL/min

• He – 10 mL/min

• Sensitivity in Low Resolution: 3220 V/ppm

• Blank 39K = 230 mV

• Cup Configuration:

Operation Mode 1 – Potassium method and peak scan

Cup L4 L2 L1 C H1 H2 H3

Mass 38Ar 39K 40Ca 41K 42Ca 43Ca

Amplifier 1011Ω 1010Ω 1011Ω 1011Ω 1011Ω 1011Ω 1011Ω0

50

100

150

200

250

300

350

400

450

500

40.47 40.49 40.51 40.53 40.55 40.57 40.59 40.61

VMass (µ)

38Ar

39K

40Ca

41K

42Ca

43Ca

Operation Mode 1 – Potassium isotope ratios

• 150 ppb K in 2% HNO3

• 3-minute measurement, bracketed

-0.20

-0.15

-0.10

-0.05

0.00

0.05

0.10

0.15

0.20

δ4

1K

(‰

)

δ41K = -0.005 ± 0.059 ‰ (2SD)

39K 40Ca 41K 42Ca 43Ca

Mean 447.89 2.32 34.90 0.02 0.00

SD 2.23 0.01 0.17 0.00 0.00

2SD 4.46 0.02 0.35 0.00 0.00

41K/39K SE 2SE δ41K SE 2SE

Mean 0.077919 0.000003 0.000005 -0.005 0.036 0.071

SD 0.000004 0.030

2SD 0.000009 0.059

Operation Mode 2 – Band pass and mass shift reaction scheme

CRC

Multicollector

Full mass spectrum from

plasma

Vienna pre-cell mass filter

set to bandpass mode to

select a narrow mass range

going into CRC

Reactive gas is added to the

cell to promote analyte ions

to higher mass molecules

e.g. Ti+O2 >> TiO + O.

Isotope measurements are

made on molecules which

are measured on a clean

background (without 48Ca

and 50Cr).

He + SF6 gas

• Band pass with Vienna pre-cell mass filter

• Ar and related species can be excluded from the cell

• Selective mass shift reactions of analyte or interferences

using reactive gases e.g. O2, N2O, NH3, SF6

• MS/MS or ‘triple quad’ approach

• E.g. Rb-Sr or Ti

Operation Mode 2 – Proteus: Effect of Ar on TiO reaction

Bandpass mode – no Ar Full transmission – Ar into reaction cell

63.86 63.88 63.90 63.92 63.94 63.96 63.98 64.00 64.02

Mass (μ)

44CaO IC3 echo

46TiO IC4 echo

47TiO IC5 echo

50TiO IC6 echo

51VO IC7 echo

52CrO IC8 echo

48TiO C echo (cps)

48TiO IC1 echo1

10

100

1000

10000

100000

1000000

63.86 63.88 63.90 63.92 63.94 63.96 63.98 64.00 64.02

Sig

nal (c

ps)

Mass (μ)

48TiO IC1 echo

44CaO IC3 echo

46TiO IC4 echo

47TiO IC5 echo

50TiO IC6 echo

51VO IC7 echo

52CrO IC8 echo

Operation Mode 2 – Vienna: TiO reaction and mass window

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1

39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65

V

Mass (µ)

4B

6B

Mass Range of Ti

incl. Ca and Cr

Central mass of

bandpass window: 48Ti

Mass Range of TiO

No Ca and Cr

ArO reduced as

mass window is

tightened40Ar almost

eliminated as mass

window is

tightened

ArN reduced as

mass window is

tightened

CO2

O3

Pre-filter

magnet field

40 %

60 %

Operation Mode 2 – Vienna: TiO preliminary data

• 48Ti/47Ti precision of 9 ppm

(10 minutes measurement)

• Interferences less than 1

mV in LR in dry plasma

• More interferences in wet

plasma

• TiO reaction yield >90%

• TiO sensitivity of ca. 2000

V/ppm in dry plasma and

LR with Jet interface

compared to 27 V/ppm

with Proteus

0

1

2

3

4

5

6

7

63.84 63.88 63.92 63.96 64 64.04

V

Mass (μ)

46TiO

47TiO

48TiO

49TiO

50TiO

0.00001

0.0001

0.001

0.01

0.1

1

10

63.8 63.9 64 64.1 64.2

V

Mass (μ)

46TiO

47TiO

48TiO

49TiO

50TiO

Conclusions

• Project Vienna solved remaining disadvantages of Proteus

• Sensitivity as good as or even better than Neptune XT

• Stable measurements of isotope ratios without negative effects from quadrupole

• Full CRC capabilities of standard collision scheme and band pass & mass shift reaction scheme

• Experience from evaluation of Project Vienna is now transferred into Neoma MS/MS