TechnicalNOTE
LCT PREMIER: POSITIVE/NEGATIVE
IONISATION SWITCHING
Waters Corporation, MS Technologies Centre, Manchester, UK
Introduction
The Waters® LCT Premier™ Mass Spectrometer is
the highest performance bench-top orthogonal
acceleration time-of-flight (oa-TOF) LC/MS system
available today. The innovative design and
hardware enhancements to our original LCT™ Mass
Spectrometer’s design provide the user with the
capabilities of positive/negative source ionisation
capabilities on a per-injection basis, but even faster
than before. With new detector and electronic
components, the instrument can switch from positive
to negative ion, or vice versa, in a minimum of
200 milliseconds, or 300 milliseconds for exact
mass measurement.
Positive/negative ionisation switching provides the
user with the capability of analyzing samples during
LC/MS experiments without needing to know a
compound’s particular ionisation mode. This is ideal
for screening applications or when multi-component
mixtures are being analyzed. Even at 300 milliseconds
switching time, exact mass measurements can be
carried out—and all this during LC time scales.
Figure 1 shows a mass spectrum of raffinose analysed
with positive/negative electrospray ionisation. With
300 milliseconds switching on the LCT Premier, the
exact mass measurements are within 3 ppm. The lower
spectrum shows the ES+ [M+Na]+ ion of raffinose and
the upper spectrum shows the ES- [M-H]- ion. Both
exact mass measurements obtained from the single
LC/MS analysis are within 2 ppm of actual mass.
Figure 1. Positive/Negative switching analysis
of Raffinose.
TechnicalNOTE
Figure 2 shows another example of positive/
PE 100ug/ml
A
PASSIFLORA111103_006
3.35
100
negative ionisation switching and its usefulness
2: TOF MS ES-
8.81
4.16 5.65
15.32
for complex mixture analysis. Figure 2 shows the
%
11.61
B
LC/MS chromatograms for the ES+, ES- and diode
array trace for a natural product extract. Figure 3a
and 3b shows the simultaneous exact mass spectra
0
PASSIFLORA111103_006
100
1: TOF MS ES+
1.74
2.24
A
3.32
%
8.83
5.63
B
obtained for both peak A (iso-orientin) and peak B
0
A
PASSIFLORA111103_006
100
(kaempforol-3-rutinoside) from the same injection. All
exact mass measurements are within 2 ppm of actual
providing highly specific answers.
5: Diode Array
8.83
3.35
5.63
4.18
%
15.35
B
0
5.00
10.00
15.00
20.00
25.00
30.00
35.00
40.00
LCT Premier: oa-TOF providing simultaneous exact
Figure 2. Positive/Negative ionisation of a
mass measured positive/negative ionization.
Passiflora extract.
PE 100ug/ml
PE 100ug/ml
PASSIFLORA111103_006
447.0923
100
HO
O
OH
O
HO
%
OH
HO
2: TOF MS ES-
A= Iso-orientin
[M-H]- = C21H19O11
Exact mass = 447.0927
Error mDa= -0.4
Error ppm= -1.0
OH
PASSIFLORA111103_006
593.1500
OH
100
O
OH
H3C
%
O
O O
OH
O
OH
2: TOF MS ES-
B=Kaempferol-3-rutinoside
[M-H]- = C27H29O15
Exact mass = 593.1506
Error mDa= -0.6
Error ppm= -1.0
O
HO
O
HO
OH
HO
OH
594.1536
OH
HO
0
0
PASSIFLORA111103_006
449.1079
100
471.0892
1: TOF MS ES+
A= Iso-orientin
[M+H]+ = C21H21O11
Exact mass = 449.1084
Error mDa= -0.5
Error ppm= -1.1
PASSIFLORA111103_006
595.1669
100
%
0
100
Time
50.00
45.00
1: TOF MS ES+
B=Kaempferol-3-rutinoside
[M+H]+ = C27H31O15
Exact mass = 595.1663
Error mDa= 0.6
Error ppm= 1.0
%
150
200
250
300
350
400
450
500
550
600
650
700
750
800
850
900
950
m/z
1000
0
100
150
200
250
300
350
400
450
500
550
600
650
700
750
800
850
900
950
m/z
1000
Figure 3a. Positive/Negative ionisation mass spectra
Figure 3b. Positive/Negative ionisation mass spectra
of Iso-orientin (Peak A).
of Kaempferol-3-rutinoside (Peak B).
TechnicalNOTE
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©2004 Waters Corporation Produced in the U.S.A. September 2004 720000931EN LL-PDF