Takaishi R, Sakai Y, Hiraoka K, Wada H, Morita S, Nakashima T, Nonami H
Clean Energy Research Center, University of Yamanashi, Takeda-4, Kofu, 400-8511, Japan.
Kyushu Okinawa Agricultural Research Center, National Agriculture and Food Research Organization (NARO), 496 Izumi, Fukuoka, 833-0041, Japan.
Rapid Commun Mass Spectrom. 2015 Aug 15;29(15):1420-6. doi: 10.1002/rcm.7240.
In electrospray droplet impact (EDI) developed in our laboratory, an atmospheric pressure electrospray source has been used. To increase the ion beam intensity and reduce the evacuation load, a vacuum electrospray cluster ion source using a silica capillary was developed.
A silica capillary with a tip inner diameter of 8 µm was used for vacuum electrospray using aqueous 10% methanol. To stabilize the flow rate of the liquid for nano-electrospray, a home-made constant pressure liquid pump was also developed.
By using the silica tip nano-electrospray emitter and a constant pressure pump, stable electrospray with flow rate of 22 nL/min was realized without using any heating system such as laser irradiation. Comparative study of mass spectra obtained by atmospheric pressure EDI (A-EDI) and vacuum EDI (V-EDI) was made for various samples such as thermometer molecule, peptide, polystyrene, Alq(3), NPD, C(60), indium, and SiO(2). V-EDI showed slightly milder ionization than A-EDI.
Because V-EDI gave higher target current (5-10 nA) than A-EDI (a few nA at most), V-EDI secondary ion mass spectrometry (SIMS) would be a useful technique for the surface and interface analysis.
在我们实验室开发的电喷雾液滴撞击（EDI）中，使用了大气压电喷雾源。为了提高离子束强度并减少抽气负载，开发了一种使用二氧化硅毛细管的真空电喷雾簇离子源。
使用尖端内径为8 µm的二氧化硅毛细管进行10%甲醇水溶液的真空电喷雾。为了稳定用于纳米电喷雾的液体流速，还开发了一种自制的恒压液体泵。
通过使用二氧化硅尖端纳米电喷雾发射器和恒压泵，在不使用任何加热系统（如激光照射）的情况下实现了流速为22 nL/min的稳定电喷雾。对各种样品（如温度计分子、肽、聚苯乙烯、Alq(3)、NPD、C(60)、铟和SiO(2)）进行了大气压EDI（A-EDI）和真空EDI（V-EDI）获得的质谱的比较研究。V-EDI显示出比A-EDI稍温和的电离。
由于V-EDI比A-EDI（最多几纳安）具有更高的目标电流（5-10纳安），V-EDI二次离子质谱（SIMS）将是一种用于表面和界面分析的有用技术。
