An apparatus for detecting constituents in a sample includes first and second drift tubes defining first and second drift regions, and a controllable electric field device within a fragmentation region coupled to the first and second drift tubes. The apparatus also includes a first ion shutter positioned between the first drift and fragmentation regions. The apparatus further includes a control system configured to regulate the first ion shutter, thereby facilitating injection of a selected portion of ions from the first drift region into the fragmentation region. The control system is also configured to regulate the controllable device to modify the selected portion of ions to generate predetermined ion fragments within the fragmentation region, thereby facilitating injection of a selected portion of the predetermined fragmented ions into the second drift region. A method of detecting constituents in a sample is facilitated through such an apparatus.

A Time of Flight mass spectrometer is disclosed wherein a fifth order spatial focusing device is provided. The device which may comprise an additional stage in the source region of the Time of Flight mass analyser is arranged to introduce a non-zero fifth order spatial focusing term so that the combined effect of first, third and fifth order spatial focusing terms results in a reduction in the spread of ion arrival times T of ions arriving at the ion detector.

A mass spectrometer is disclosed comprising an ion mobility spectrometer or separator and an ion guide arranged downstream of the ion mobility spectrometer or separator. A plurality of axial potential wells are created in the ion guide so that ions received from the ion mobility spectrometer or separator become confined in separate axial potential wells. The potential wells maintain the fidelity and/or composition of ions received from the ion mobility spectrometer or separator. The potential wells are translated along the length of the ion guide.

A metallic plate holder 3 is directly placed on a flat bottom plate 1a of a sample chamber. A linear guide 21 extending in x-direction is located below the bottom plate. Another linear guide 22 extending in y-direction is fixed to a movable part 21a of the linear guide 21. A magnet 23, fixed to a movable part 22a of the linear guide 22, magnetically attracts the plate holder across the bottom plate. When the magnet is two-dimensionally driven by the linear guides, the plate holder follows it and moves two-dimensionally. The flat bottom plate limits the z-position of the plate holder, thereby reducing the fluctuation in the level of the sample on a sample plate 2 due to the movement. Thus, the variation in the level at different positions on the sample plate is reduced, so that the number of times of a calibrant measurement can be decreased.

Four main rod electrodes included in a main electrode section are disposed in a rotationally symmetric manner around an ion optical axis. Among four pre-rod electrodes included in a pre-electrode section disposed in front of the main electrode section, two are in contact with a circle of a radius r.sub.0, whereas the other two are disposed to be in contact with a circle of a radius R.sub.0 larger than r.sub.0, resulting in rotational asymmetry around the ion optical axis. Accordingly, a shape of acceptance on an x-y plane regarding positions of ions in the pre-electrode section becomes elliptical. This allows the shape of the acceptance to become gradually flat as the ions travel along the ion optical axis, reducing a mismatch between emittance of incoming ions and the acceptance on a receiving side, and relieving ion loss during ion introduction.

When a normal mass spectrometry is performed without dissociating an ion, the m/z range limitation voltage setting unit applies a radio-frequency voltage to each rod electrode of the quadrupole mass filter and controls the quadrupole voltage generator so as to apply a direct current voltage smaller than that at the time of ion selection for MS/MS spectrometry. When a small direct current voltage is applied, a mass scanning line is set so as to pass through a stability region on a Mathieu diagram over a long range, hence large m/z ions that do not fall within the stability region are blocked in the quadrupole mass filter. By adjusting a cut-off point on larger m/z side blocked in accordance with the measurement period of OA-TOFMS including the orthogonal accelerator, heavy ions that cause period delay are prevented from being introduced into the orthogonal accelerator.

A voltage applied to an exit gate electrode forming a potential barrier and temporarily trapping ions within the inner space of the ion guide is higher than a voltage at an ion guide's exit end. A higher voltage is applied to the exit gate electrode for a lower m/z value of the measurement target ion, to push back the ion which has slowly moved along a potential gradient and reached the exit end of the ion guide. An ion having a lower m/z value is more likely to be located in a farther region from the exit end and forced to travel a longer distance when voltage applied to the exit gate electrode is lowered. A lower m/z value also means a higher travelling speed toward the orthogonal accelerator, whereby m/z dependency of the time required for travel from the ion guide to the orthogonal accelerator eventually becomes low.

Elongation of orthogonal accelerators is assisted by ion spatial transverse confinement within novel confinement means, formed by spatial alternation of electrostatic quadrupolar field (22). Contrary to prior art RF confinement means, the static means provide mass independent confinement and may be readily switched. Spatial confinement defines ion beam (29) position, prevents surfaces charging, assists forming wedge and bend fields, and allows axial fields in the region of pulsed ion extraction, this way improving the ion beam admission at higher energies and the spatial focusing of ion packets in multi- reflecting, multi-turn and singly reflecting TOF MS or electrostatic traps.

A Time of Flight mass analyser is disclosed comprising: at least one ion mirror ((34) for reflecting ions; an ion detector (36) arranged for detecting the reflected ions; a first pulsed ion accelerator (30) for accelerating an ion packet in a first dimension (Y-dimension) towards the ion detector (36) so that the ion packet spatially converges in the first dimension as it travels to the detector (36); and a pulsed orthogonal accelerator (32) for orthogonally accelerating the ion packet in a second, orthogonal dimension (X-dimension) into one of said at least one ion mirrors (34).

A multipole ion guide (30) including a plurality of rod electrodes arranged at an angle to the central axis (C) is placed within a collision cell (13) located in the previous stage of an orthogonal accelerator (16). Radio-frequency voltages with opposite phases are applied to the rod electrodes of the ion guide (30) so that any two rod electrodes neighboring each other in the circumferential direction have opposite phases of the voltage. A depth gradient of the pseudopotential is thereby formed from the entrance end toward the exit end within the space surrounded by the rod electrodes, and ions are accelerated by this gradient. During an ion-accumulating process, a direct voltage having the same polarity as the ions is applied to the exit lens electrode (132) to form a potential barrier for accumulating ions. Among the ions repelled by the potential barrier, ions having smaller m/z return closer to the entrance end. Therefore, when the potential barrier is removed and ions are discharged, ions having smaller m/z are discharged at later points in time than those having larger m/z. Therefore, a wide m/z range of ions can be simultaneously accelerated and ejected by an orthogonal accelerator (16).