Sample quantitation using a miniature mass spectrometer
The invention generally relates to sample analysis with a miniature mass spectrometer. In certain embodiments, the invention provides methods that involve generating ions of a first analyte and ions of a second analyte. Those ions are transferred through a discontinuous sample introduction interface into a first ion trap of a mass spectrometer in a manner in which the discontinuous sample introduction interface remains open during the transferring. The discontinuous sample introduction interface is closed and the ions are sequentially transferred to a second ion trap of the mass spectrometer where they are sequentially analyzed.
1. A method for analyzing a sample and an internal standard in a miniature mass spectrometer, the method comprising:
generating sample ions and internal standard ions;
simultaneously transferring the sample and internal standard ions through a discontinuous sample introduction interface (DAPI) into a first ion trap of the miniature mass spectrometer, wherein the first ion trap is a first rectilinear ion trap that comprises top and bottom electrodes that are y electrodes and left and right electrodes that are x electrodes;
closing the discontinuous sample introduction interface;
sequentially transferring the sample and internal standard ions to a second ion trap of the miniature mass spectrometer, wherein the second ion trap is a second rectilinear ion trap that comprises top and bottom electrodes that are y electrodes and left and right electrodes that are x electrodes and wherein the first and second ion traps share a common end mesh electrode; and
sequentially analyzing within one second of each other the sample and internal standard ions in the second ion trap, wherein during a trapping step, a DC voltage is applied to the common end mesh electrode and single phase Radio Frequencies (RFs) of 1015 kHz and 995 kHz are applied on y electrodes of the first and second rectilinear ion traps, respectively, and after the trapping step and in order to then achieve an axial mass selective ejection, the ions trapped in the first rectilinear ion trap during a DAPI opening period undergo axial mass selective ejection toward the second rectilinear ion trap via application of one of the two following methods: (i) a separate RF scan with a resonance ejection by a dipolar AC, or (ii) an AC excitation with a separate steady RF.
2. The method according to claim 1 , wherein generating the ions is by a technique that utilizes an ionization source that operates at atmospheric pressure and temperature.
3. The method according to claim 1 , wherein generating the ions is by a technique that utilizes a direct ambient ionization/sampling technique.
4. The method according to claim 3 , wherein the technique is paper spray ionization.
5. The method according to claim 1 , wherein the sample and internal standard ions are transferred to the second ion trap within a single scan cycle.
6. The method according to claim 1 , wherein analyzing comprises taking MS/MS measurements.