design and performance of a second source …lewis, witold niklewski, mark pickering, graham...
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INTRODUCTION
Interest in ion mobility (IM) separation continues to grow and
it is now utilised over a broad range of application areas.
Over the last ten years or so there has been a notable
advance in ion mobility technology coupled with mass
spectrometry with significant increases in mobility resolution
and the prospect of additional instrument functionality [1-4].
One such system is a travelling wave (T-Wave) driven multi-
pass cyclic ion mobility (cIM) separator embedded in a Q-ToF
instrument [3]. Here we report on the preliminary design and
performance of a second-generation research platform with
enhancements to the ion optics, ToF mass analyser, detection
system and instrument control.
DESIGN AND PERFORMANCE OF A SECOND-GENERATION CYCLIC ION MOBILITY ENABLED Q-TOF Kevin Giles, Jakub Ujma, Jason Wildgoose, Martin R. Green, Keith Richardson, David Langridge, Nick Tomczyk Waters Corporation, Altrincham Road, Wilmslow SK9 4AX, UK.
Two 45mm long stacked ring ion guides (SRIGs), with axial
fields, are positioned either side of the array. These can be
used for ion transport or trapping. At the entry to the high-
pressure region there is a standard He cell. Either side of the
high-pressure region are 150mm long SRIG devices with
axial fields operating around 10-2
mb. The cIM was operated at
1.8mb of N2 and T-Waves in the range 35 to 43V at 375ms-1
.
Time-of-Flight Analyser
The new ToF analyser has an offset V/W geometry (Fig. 1),
providing 40/120cm longer flight path respectively than the
previous analyser. Further, to improve the ToF resolution vs
transmission characteristics, the standard transfer T-Wave
SRIG was replaced with a segmented quadrupole device
operating with an axial field (Fig. 2a). This quadrupole
provides optimal conditioning of the ion beam prior to entry
into the orthogonal acceleration region of the ToF. See poster
TP 391 for further description of the ToF and quadrupole
guide.
Acknowledgements
We are grateful to Bharat Chande, James Harrison, Darren Hewitt, John Iveson, John
Lewis, Witold Niklewski, Mark Pickering, Graham Scambler and Chris Wheeldon at
Waters Wilmslow for their involvement in the design and construction of the cyclic IM
research platform.
References
1. Koeniger et al, An IMS-IMS Analogue of MS-MS, Anal. Chem., 2006, 78, p4161
2. Merenbloom et al, High-Resolution Ion Cyclotron Mobility Spectrometry, Anal.
Chem., 2009, 81, p1482
3. Giles et al, Characterising a T-Wave Enabled Multi-pass Cyclic Ion Mobility
Separator, ASMS 2015 Proceedings, St Louis
4. Deng et al, Serpentine Ultralong Path with Extended Routing (SUPER) High
Resolution Traveling Wave Ion Mobility-MS using Structures for Lossless Ion
Manipulations, Anal. Chem., 2017, 89, p4628
5. Green et al, A Novel Wide Dynamic Range oa-ToF Detection System Based on
Dual 10-bit ADCs and FPGA Processing, ASMS 2016 Proceedings, San Antonio
CONCLUSION
A second-generation cyclic IM-enabled Q-Tof research platform has been built
Mobility resolution in excess of 500 (Ω/∆Ω) indicated for reverse sequence peptides SDGRG and GRGDS
Improved m/z and mobility transmission window using pre/post cyclic IM SRIGs with axial field
IMSn capability illustrated using the (M+6H)
6+ charge state of
bovine ubiquitin
m/z resolution of up to ~120,000 demonstrated with offset V/W geometry ToF analyser and dual gain ADC detection system.
OVERVIEW
Investigations into the design and characteris-
tics of a new Q-cyclic ion mobility-ToF platform based on Synapt G2-Si architecture
Mobility resolution over 500 (Ω/ΔΩ) indicated
m/z resolution up to 120,000
IMSn functionality
Increased detection system dynamic range
EXPERIMENTAL
The new platform is based on a Synapt G2-Si (ESI-Q-IM-ToF) instrument and is shown schematically in Figure 1. All samples were introduced by infusion through an ESI source.
Cyclic Ion Mobility
The new cIM arrangement is shown in Figure 2a. The cyclic device and array are the same as the original prototype instrument and provide a 100cm, single pass, mobility path length; however the new device is built from four quadrants (Fig. 2b), for ease of construction, compared to the single unit design of the first version.
RESULTS
The mobility separation characteristics of the new system
have been investigated by infusion of a mixture of the reverse
sequence peptides SDGRG and GRGDS. Figure 4a shows
the multipass separation of the (M+H)+ ions at m/z 491.2.
Figure 4b is a plot of resolution vs number of passes (n)
around the cyclic device, with the fitted curve (red)
highlighting the expected n dependence. For the data
points beyond n=18, the more mobile SDGRG ions have
caught up with the less mobile GRGDS ions in the cyclic
device and so the individual species were mobility selected
and allowed to cycle for more passes. The inset plot in Figure
4b is a composite plot of the arrival time distributions
(ATD) of the two individual species for 50 passes, from which
a resolution of ~550 is indicated.
TrapT-Wave
TransferQuad
SRIG SRIGArrayHeCell
SRIG SRIG
Cyclic IM
~1.8mb
(a)
(b)
Figure 2. (a) Mechanical drawing and outline of the cIM region. (b) Pho-
to of the cIM device and a quadrant section (inset).
Detection System
The standard Synapt detection system (8-bit, 3.0GHz
analogue-to-digital converter (ADC)) has been replaced with
a dual gain system [5], operating with two 10-bit, 3.6GHz
ADCs with independent analogue pre-amplifiers of different
gain. The combined output of the two ADCs is up-sampled to
7.2GHz and provides up to 6 decades of in-spectrum dynamic
range. This represents a 60-fold increase compared to the
standard acquisition system.
Instrument Control
The instrument control system utilised comprises a highly
configurable web-based graphical user interface for tuning, as
well as a Lua scripting environment, allowing design and
adjustment of custom acquisition modes. Each operating
mode of the cIM device is described by a short segment of
XML detailing the voltages to be applied and a duration. A full
cyclic sequence consists of a block of these XML segments
which can be embedded in a Lua script (Fig. 3).
Figure 3. XML code providing the IM sequence: inject(0)/separate(3)/
eject-detect(7). Times are specified in ms, other settings in volts.
The prototype cIM instrument utilised a long, high-pressure,
post-mobility T-Wave transfer device which required specific,
mobility range dependent, wave settings to maintain temporal
fidelity. The second generation system has a much shorter
SRIG with axial field. Figure 5 shows the comparative
transmission windows for the two systems. The high mobility
(and low m/z) cut off in Figure 5a is due to the fixed amplitude
T-Wave rejecting these ions.
The multifunction capability of the cIM is illustrated in Figure
6. Here the (M+6H)6+
charge state of bovine ubiquitin has
been m/z selected for mobility separation. Figure 6a shows
the 1 pass separation for the non-activated and pre-cIM
collisionally activated ions. Figure 6b shows the sequence of
1 pass separation with a 1ms segment of the separated ions
being ejected and stored in the pre-array SRIG, followed by
the 1 pass separation of these ions following re-injection to
the cIM. Figure 6c shows an expanded view the 1 pass
separation of the segment re-injected under both non–
activating and activating conditions. The activated species
(generated by collisional activation on re-entry to the array)
has an ATD close to that in Figure 6a but in this case
originates from a sub-section of precursor ions.
JU_20161202_alpha_MM _highmz_1spin.raw : 1
JU_20161114_beta_M M_1spin.raw : 1
100 500 1000 1500m/z
0
5
10
Dri
ft T
ime
(ms)
0
5
10
Dri
ft T
ime
(ms)
Inte
nsi
ty
0
1
Inte
nsi
ty
0
1
Figure 5. Plots of m/z and arrival time vs m/z for a tuning solution (a)
prototype cyclic instrument (b) latest generation cyclic platform.
(a)
(b)
0 40 80 120 160 200 240 280 320 360 400
Nor
mal
ised
Inte
nsity
Arrival Time (Bins)
0 20 40 60 80 100 120 140 160 180 200
Nor
mal
ised
Inte
nsity
Aligned Arrival Time (Bins)
0 20 40 60 80 100 120 140 160 180 200
Nor
mal
ised
Inte
nsity
Arrival Time (bins)
Ubiquitin 6+Not activatedActivated
1.0 ms Segment
Segment1 pass
(a)
(b)
(c)
Raw output
m/z1425 1426 1427 1428 1429 1430 1431 1432
%
0
100
Figure 6. Arrival Time plots for Ubiquitin (M+6H)6+
(a) single pass sepa-
ration (b) 1 ms segment selected from single pass ions followed by a sin-
gle pass on the ions from the segment (IMS2) (c) expanded view of se-
lected segment plot, with and without pre-separation activation.
0 10 20 30 40 50
0
100
200
300
400
500
600
Re
so
lutio
n
Number of Passes
Model Allometric1
Equation y = a*x^b
Plot Resolution
a 77.58079 ± 1.11603
b 0.50458 ± 0.0045
Reduced Chi-Sqr 26.51152
R-Square(COD) 0.99854
Adj. R-Square 0.99847
460 465 470 475 480 485 490 495 500
Time (ms)
SDGRG (1+) GRGDS (1+)
(a)
(b)
Figure 4. Mobility separation of singly charged SDGRG and GRGDS
ions (a) ATD vs number of passes, (b) resolution vs number of passes.
Inset are individual mobility spectra obtained for 50 passes.
m/z 491.2
SDGRG (1+)205.3 Ų
GRGDS (1+)208.5 Ų
ResolutionΩ/∆ Ω
71
104
149
219
317
Figure 1. A schematic diagram of the Q-cIM-ToF platform.
SourceQuadrupole
Cyclic IM
ToFAnalyser
Ion optics
a
b
c d
a - pusherb - V reflectronc - W reflectrond - detector
Figure 7. High resolution data. 2D plot of arrival time vs m/z for the
(M+6H)6+
charge state of bovine ubiquitin (collisionally activated).
30 35 40 45 50
Arrival Time (ms)
Ubiquitin 6+
(mw 8559.6)
2 Passes
m/z res
~120,000
Mobility res ~100
(for 1+ species)
JU_20170518_Ubi6_highres_2passe s_act_repeat.raw : 1
1427.5
1428
1428.5
1429
1429.5
m/z
The longer ToF analyser and dual gain ADC detection system
provide higher m/z resolution and higher dynamic range. Fig-
ure 7 is a plot showing data acquired in the ‘W’ mode of
ToF operation and 2 passes around the cyclic IM device. A
maximum m/z resolution of ~120,000 hass been obtained in
the ‘W’ mode and ~65,000 in the ‘V’ mode.