Improved Miniaturized Linear Ion Trap Mass Spectrometer Using Lithographically Patterned Plates and Tapered Ejection Slit.

We present a new two-plate linear ion trap mass spectrometer that overcomes both performance-based and miniaturization-related issues with prior designs. Borosilicate glass substrates are patterned with aluminum electrodes on one side and wire-bonded to printed circuit boards. Ions are trapped in the space between two such plates. Tapered ejection slits in each glass plate eliminate issues with charge build-up within the ejection slit and with blocking of ions that are ejected at off-nominal angles. The tapered slit allows miniaturization of the trap features (electrode size, slit width) needed for further reduction of trap size while allowing the use of substrates that are still thick enough to provide ruggedness during handling, assembly, and in-field applications. Plate spacing was optimized during operation using a motorized translation stage. A scan rate of 2300 Th/s with a sample mixture of toluene and deuterated toluene (D8) and xylenes (a mixture of o-, m-, p-) showed narrowest peak widths of 0.33 Th (FWHM). Graphical Abstract ᅟ.

Optimal fabrication methods for miniature coplanar ion traps.

RATIONALE: Ion trap mass spectrometers are beneficial due to their intrinsic sensitivity and specificity. Therefore, a portable version for in situ analysis of various compounds is very attractive. Miniaturization of ion traps is paramount for the portability of such mass spectrometers. METHODS: We developed an optimized design for a planar linear ion trap mass spectrometer, consisting of two trapping plates with photolithographically patterned electrodes. Each plate is constructed using a machined glass substrate and standard microfabrication procedures. The plates are attached to a patterned circuit board via wire bonds then positioned approximately 5 mm apart. RESULTS: Trapped ions are detected by ejecting them through tapered slits, which alleviate charge buildup. Mass analysis can be performed through either boundary or resonant ion ejection. Better than unit mass resolution is demonstrated with resonant ejection. CONCLUSIONS: The optimized planar linear ion trap provides good resolution and the potential for further miniaturization. This was accomplished by vigorously testing variables associated with ion trap design including electrical connections, substrate materials, and electrode designs.