Helium Plasma Source Time-of-Flight Mass Spectrometry: Off-Cone Sampling for Elemental Analysis
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- 作者：Yongxuan Su ; Yixiang Duan ; and Zhe Jin
- 刊名：Analytical Chemistry
- 出版年：2000
- 出版时间：June 1, 2000
- 年：2000
- 卷：72
- 期：11
- 页码：2455 - 2462
- 全文大小：118K
- 年卷期：v.72,no.11(June 1, 2000)
- ISSN：1520-6882
文摘
In this paper, an atmospheric pressure, helium microwave-induced plasma (MIP) ion source coupled with an orthogonal acceleration time-of-flight mass spectrometer(TOFMS) is explored for elemental analysis. Studies ofthe relationship between ion signals and sampling distance of the MS reveal that background signals can besuppressed dramatically without sacrificing the signalintensities of analytes when the microwave plasma plumeis off the tip of the sampler orifice. This "off-cone" ionsampling mode provides a technique to obtain nearly"clean" background spectra and, thus, eliminates thespectral interference from entrainment air and the working-gas species, making it possible to sensitively determine isotopes that suffered from spectral interference inICPMS and MIPMS (such as 40Ca, 52Cr, 55Mn, and 56Fe). On the other hand, since the high-temperatureplasma is kept away from the sampler aperture, off-conesampling places little demand on the cooling device andthe lifetime of the sampler plate can be extended. Theinstrumental system can provide a fairly good massresolution of 1100 (fwhm). The detection limits (3
) inthe tens of picograms per milliliter level for the elementsstudied can be achieved with a digital oscilloscope. Thesedetection limits can be easily improved with an advanceddetection system, which is currently available in commercial markets.
) inthe tens of picograms per milliliter level for the elementsstudied can be achieved with a digital oscilloscope. Thesedetection limits can be easily improved with an advanceddetection system, which is currently available in commercial markets.