Biology Reference
In-Depth Information
Fig.
2
(
a
) Diagram of the stability regions of a quadrupole ion trap according to the voltage and frequency
applied to the ion trap elements. From Patent 5399857 “Method and apparatus for trapping ions by increasing
trapping voltage during ion introduction” US Patent Issued on March 21, 1995. (
b
) Trajectory of an
m
/
z
105 ion
trapped in a 3D Ion Trap. The projection onto the
x
-
y
plane illustrates planar motion in three-dimensional
space. The trajectory develops a shape that resembles a flattened boomerang. Taken from [
101
]. (
c
) Ion cyclo-
tron resonance motion of an ion of
m
/
z
2,300 in a 2 in. cubic Penning trap in a perfectly homogeneous mag-
netic field of 3 T, for 10 V trapping voltage [
102
]
q
m
U
a
=− =
28
a
z
r
r
2
ω
RF
0
q
m
V
q
=− =
24
q
z
r
2
ω
RF
r
0
The subscripts
z
and
r
represent, respectively, axial and radial
motion perpendicular to and between the end caps,
U
is the DC
potential on the end-cap electrodes,
V
is the RF potential applied
to the ring electrode, r
0
is the radius of the ring electrode, and ω
RF
is the RF angular frequency. Figure
2a
displays a diagram of the
stability regions of a quadrupole ion trap according to the voltage
and frequency applied to the ion trap elements, and Fig.
2b
shows
the trajectory of an
m
/
z
105 ion confined in a 3D ion trap.
A unique feature of a Paul ion trap compared with a quad-
rupole mass analyzer, which will be discussed below, is that the
former can perform multiple stage mass spectrometry (MS
n
)
simply by the use of additional operations which are performed
sequentially in time. In a typical multiple-stage mass spectrom-
etry experiment, the ion of interest is isolated, induced to
fragment by a resonance signal adjusted to cause collisionally
