Uchimura Tomohiro, Sakoda Yuji, Imasaka Totaro
Department of Applied Chemistry, Graduate School of Engineering, and Division of Translational Research, Kyushu University, 744, Motooka, Nishi-ku, Fukuoka 819-0395, Japan.
Anal Chem. 2008 May 15;80(10):3798-802. doi: 10.1021/ac8000176. Epub 2008 Mar 26.
A narrow capillary, the tip of which was restricted to form a supersonic jet, was employed for sample introduction in time-of-flight mass spectrometry. The analyte was adsorbed at the tip of the capillary, due to a temperature decrease by the Joule-Thomson effect. Then, the analyte was desorbed using a pulsed laser emitting at 532 nm, and was entrained into a carrier gas. The analyte in the jet was subsequently ionized using a pulsed laser emitting at 266 nm. The duration of the analyte passing through the ionization region was 5.4 mm in length (9 micros in time), and the signal intensity was enhanced 310-fold. This technique can also improve selectivity by controlling the nozzle temperature, since volatile compounds are not trapped at the tip of the capillary and then are not concentrated in the jet. In this approach, the analyte can be injected in a pulsed mode into a vacuum without using a complicated mechanical valve even at a repetition rate of >1 kHz from the nozzle heated at a temperature of >300 degrees C.
在飞行时间质谱分析中，采用了一根狭窄的毛细管，其尖端被限制形成超声速射流用于样品引入。由于焦耳 - 汤姆逊效应导致温度降低，分析物吸附在毛细管尖端。然后，使用发射波长为532 nm的脉冲激光使分析物解吸，并被夹带进入载气中。随后，使用发射波长为266 nm的脉冲激光使射流中的分析物离子化。分析物通过电离区域的长度为5.4 mm（时间为9微秒），信号强度增强了310倍。由于挥发性化合物不会被困在毛细管尖端，进而不会在射流中浓缩，因此该技术还可以通过控制喷嘴温度来提高选择性。在这种方法中，即使在温度高于300摄氏度的喷嘴以大于1 kHz的重复频率下，也无需使用复杂的机械阀，就可以将分析物以脉冲模式注入真空。
