Multi-ion quantitative mass spectrometry by orthogonal projection method with periodic signal of electrostatic ion beam trap.

In this article, orthogonal projection method (OPM) is introduced which could perform multi-ion quantitative MS with signal of electrostatic ion beam trap (EIBT), and its application has been demonstrated by numerical modeling. To acquire periodic current signal, a model of EIBT with cylindrical-detector is set up to simulate ions' oscillatory motion. Whereafter, OPM is introduced and applied for quantitative MS with sampling time being as short as 200 µs. Comparing with fast Fourier transform (FFT), the MS acquired by OPM is characterized by a more readable spectrum, a much shortened sampling time and the ability to do quantitative analysis. Within the optimum sampling time range, quantitative MS could be performed with accuracy of over 90%. It is found that the lower limit and the upper limit of the optimum sampling time range are all proportional to M(3/2)/δM and its relation is specified by linear regression. Aided by the results of FFT, OPM is applied to a compound tested signal induced by three kinds of ions. It shows that OPM could be performed respectively to each kind of ions without interference from other component of the signal. The resolving power acquired by OPM is about 75 000 with sampling time as short as 10 ms, and the quantitative result that acquired is quite accurate.