Triboionization in Discontinuous Atmospheric Pressure Inlet for a Miniature Ion Trap Mass Spectrometer

Abstract

Discontinuous atmospheric pressure interface (DAPI) consisting of a pinch valve, a silicone tube, and two metal capillaries has been widely used in miniature mass spectrometry. It is interesting that clear ion signals could be observed even when the extra ionization source was turned off. In-depth analysis suggested that this new ionization phenomenon known as triboionization is based on the surface friction on the inner surface of the silicone tube during the on/off of the pinch valve. In this study, triboionization in the DAPI of a miniature ion trap mass spectrometer was investigated. It was discovered that the signal intensity depended greatly on the material and the roughness of the silicone tube used in the DAPI. By rubbing the inner surface of the silicone tube, for example, the signal intensity can increase by nearly 20 times. Two connected pinch valves were developed to study the effects of the discharge pressure, the number, and the frequency of on/off of the pinch valve on triboionization, which were verified to have a large impact on the product ions. In addition, the humidity of the inner surface of the silicone tube impacted the signal intensity of product ions and the mass spectrum patterns, where the product ions were typically protonated ions. As the humidity increases, the signal intensity of analytes with high proton affinity increases accordingly. This triboionization source, which does not require heat, light, radiation, auxiliary gas, or solution, has been preliminarily proved to have potential for surface detection after continuous enrichment.

Balancing charge dissipation and generation: mechanisms and strategies for achieving steady-state charge of contact electrification at interfaces of matter

“…Another fascinating application involves the ionization of gas molecules via dielectric breakdown for chemical analysis using a mass spectrometer. 104 Static charge was first generated on the inner surface of a silicone tube (inner diameter of 1 mm) by contact electrification of the inner surface (i.e., via pressing the "pinch valve"; Figure 6d). A vapor containing the analyte (i.e., anisole) was passed through the tube and analyzed using a mass spectrometer.…”

“…(d and e) Reproduced with permission (copyright 2021, American Chemical Society). 104 (f) Scheme illustrates the operation of a DC-TENG (direct-current triboelectric nanogenerator), and (g) current obtained by the DC-TENG in air and oxygen (O 2 ) under atmospheric pressure. (f and g) Reproduced with permission (copyright 2021, Elsevier).…”

“…For supplying large quantities of charge rapidly into gas, one common way is to generate static charge by contact electrification and dissipate the charge by the dielectric breakdown of the gas (Section 3.1). We discussed the many important applications of this process in the section on dielectric breakdown; the applications include air ionizers, 103 MS, 104 DC-TENGs, 105 surface treatment, 83 and luminescence. 193 For example, the DC-TENG requires the generation of a large amount of static charge and fast dissipation via dielectric breakdown for producing an electric current that powers devices (Section 3.1.7).…”

“…The signal was weak (i.e., by less than 20 times) when the tube was not roughened ("Before Rubbing"). (d and e) Reproduced with permission (copyright 2021, American Chemical Society) 104. (f) Scheme illustrates the operation of a DC-TENG (direct-current triboelectric nanogenerator), and (g) current obtained by the DC-TENG in air and oxygen (O 2 ) under atmospheric pressure.…”

Portable particle mass spectrometer

“…The particles were directly sucked into the ion trap when the pinch valve of the DAPI opened. [26][27][28][29][30][31] CAPI is the other vacuum system used for a miniaturized mass spectrometer, 32,33 but only for small molecule instead of particles currently. The CAPI let air samples introduced continuously.…”