Ion source for liquid matrix secondary ionization mass spectrometry.
Ion source for liquid matrix secondary ionization mass spectrometry.
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DOI：
10.1021/ac00298a009
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发表时间：
1986-06
影响因子：
7.4
通讯作者：
Falick Am;Wang Gh;Walls Fc
中科院分区：
文献类型：
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作者：
Falick Am;Wang Gh;Walls Fc
采用Cs+初级束的大规模二次离子质谱（LSIMS）离子源已经构建，并且其性能已经与使用Xe原子的标准Kratos MS-50快原子轰击（FAB）源进行了比较。LSIMS源具有改进的高压馈电（20 kV）、机械Cs+枪位和|USTER和更高效的二次离子收集光学器件。发现LSIMS源在使用0.1pA Cs+初级束时，最大准分子离子（MH+或M+ Na+）强度增加约2倍，在使用1.0pA初级束时增加约5倍。样品光谱也被发现持续时间显着更长的LSIMS源。在整个样品寿命内的积分强度测量表明，LSIMS源比FAB源灵敏10-20倍。改进的光学系统和聚焦的初级光束都有助于增强性能。用Cs ~+离子主束进行液体基质二次电离质谱（LSIMS），在本实验室已成功应用多年。所用的方法和获得的光谱与快原子轰击（FAB）质谱法非常相似（1）。然而，在操作中，Cs+原束的使用比中性铯原子束具有某些重要的优点。首先，离子束在强度、能量和聚焦方面比中性束更容易控制。在所有这些实验（2）中使用的Cs+枪中，加热含有铯铝硅酸盐的烘箱以产生Cs+。通过改变加热器功率，可以容易地实现对总束流的控制。一次粒子能量由电子枪和离子源块之间的电位差决定，电子枪采用单透镜透镜，使一次粒子束聚焦到样品上。Cs+枪相对于常用中性原子枪的第二个主要优点是降低了离子源区域，特别是源狭缝的污染水平。自从新的Cs+枪投入常规运行以来，对源和源狭缝的清洁要求已大大降低。此外，总体源压力在操作中显著低于使用常规中性原子枪时。中性原子枪使用电荷交换单元，其不断地通过原子束出口孔将中性气体排放到离子源外壳中。最后，Cs+炮结构紧凑
(LSIMS) ion source employing a Cs+ primary beam has been constructed, and its performance has been compared against a standard Kratos MS-50 fast atom bombardment (FAB) source using Xeatoms. The LSIMS source has improved high-voltage feedthroughs (20 kV), a mechanical Cs+ gun position ad| uster, and more efficient secondary ion collection optics. The LSIMS source was found to give approximately a factor of 2 Increase In maximum quasl-molecular ion (MH+ or M+ Na+) intensity when a 0.1 pA Cs+ primary beam was used, and a factor of 5 with a 1.0 pA primary beam. The sample spectra were also found to last significantly longer with the LSIMS source. A measurement of Integrated inten-sity over the total sample lifetime showed the LSIMS source to be a factor of 10-20 more sensitive than the FAB source. Both the Improved optics and the focused primary beam contribute to the enhanced performance. The mass spectra obtained were observed to be essentially the same regardless of which primary beam was used.Liquid matrix secondary ionization mass spectrometry (LSIMS) using a Cs+ ion primary beamhas been used suc-cessfully in this laboratory for several years. The methods used andthe spectra obtained are very similar to Xe fast atom bombardment (FAB) mass spectrometry (1). However, in operation, the use of a Cs+ primary beam has certain im-portant advantages over a neutral Xe atom beam. First, an ion beam is much easier to control in intensity, energy, and focusing than a neutral beam. In the Cs+ gun used in all of these experiments (2) an oven containing a cesium alumina silicate is heated to produce Cs+. Control of total beam flux is easily achieved by varying the heater power. The primary particle energy is determinedby the applied potential dif-ference between the gun and the ion source block, and the gun is constructed with an Einzel lens so that the primary beam can be focused onto the sample. A second major advantage of the Cs+ gun over commonly used neutral atom guns is the reduced level of contamination of the ion source region, particularly the source slit. Cleaning of the source and source slit has been required much less frequently since the new Cs+ gun was placed in routine operation. In addition, the overall source pressure is significantly lower in operation than when a conventional neutral atom gun is used. Neutral atom guns use a charge exchange cell, which constantly bleeds neutral gas through the atom beam exit hole into the ion source housing. Finally, the Cs+ gun is compact