Single-particle mass spectrometry of polystyrene microspheres and diamond nanocrystals.
Single-particle mass spectrometry of polystyrene microspheres and diamond nanocrystals.
复制标题
聚苯乙烯微球和金刚石纳米晶体的单粒子质谱分析。
作者：
Y. Cai;W. Peng;S. Kuo;Y. Lee;H. C. Chang
利用电喷雾电离源与音频四极离子阱质谱仪相结合，获得了单个亚微米大小粒子的高分辨率质谱。与传统方法不同，连续氩离子激光器的光散射可以检测出从离子阱中喷射出来的粒子。通常，在每次测量中，有10个粒子被捕获和询问。音频离子阱在质量选择不稳定模式下工作时，对粒子的分析表明，它们的质量电荷比（m/z）都不同，并且观察到的质谱中的单个峰基本上来自单个粒子。在10(2)次重复实验中获得的光谱直方图相当于使用单粒子质谱仪（SPMS）同时分析10(3)个粒子的离子系综时所观察到的单光谱。为了校准这种单粒子质量谱，测量了阱内单个粒子振荡运动的长期频率，并确定了弹射点的阱参数qz。在没有离子系综效应的情况下，可以很容易地获得超过10(4)的质量分辨率。在这项工作中，我们证明了SPMS不仅可以研究单分散聚苯乙烯微球，而且还能够检测标称直径为100纳米的金刚石纳米颗粒。
High-resolution mass spectra of single submicrometer-sized particles are obtained using an electrospray ionization source in combination with an audio frequency quadrupole ion-trap mass spectrometer. Distinct from conventional methods, light scattering from a continuous Ar-ion laser is detected for particles ejected out of the ion trap. Typically, 10 particles are being trapped and interrogated in each measurement. With the audio frequency ion trap operated in a mass-selective instability mode, analysis of the particles reveals that they all differ in mass-to-charge ratio (m/z), and the individual peak in the observed mass spectrum is essentially derived from one single particle. A histogram of the spectra acquired in 10(2) repetitions of the experiment is equivalent to the single spectrum that would be observed when an ion ensemble of 10(3) particles is analyzed simultaneously using the single-particle mass spectrometer (SPMS). To calibrate such single-particle mass spectra, secular frequencies of the oscillatory motions of the individual particle within the trap are measured, and the trap parameter qz at the point of ejection is determined. A mass resolution exceeding 10(4) can readily be achieved in the absence of ion ensemble effect. We demonstrate in this work that the SPMS not only allows investigations of monodisperse polystyrene microspheres, but also is capable of detecting diamond nanoparticles with a nominal diameter of 100 nm, as well.