Abstract:
Dynamic skimmer pulsing and dynamic equilibration times are used for MS and MS/MS scans. A target percentage transmission of the ion beam is calculated based on a previous percentage transmission and a previous TIC or a previous highest intensity of a previous cycle time. An equilibration time is calculated based on the current percentage transmission and the target percentage transmission. A skimmer of a tandem mass spectrometer is controlled to attenuate the ion beam to the target percentage transmission to prevent saturation of a detector of the tandem mass spectrometer and to increase the dynamic range of the tandem mass spectrometer. The tandem mass spectrometer is controlled to perform an MS scan or an MS/MS scan after the calculated equilibration time to reduce the cycle time.
Abstract:
Sample molecules are ionized producing a beam of ions using an ion source. A plurality of ion extractions are performed on the beam of ions using a TOF mass spectrometer. Electrical detections from each extraction are measured using an ADC, producing a mass sub-spectrum for each extraction. An ion m/z from the plurality of mass sub-spectra is selected. For each mass sub-spectrum, the amplitude and m/z of an ion within a m/z tolerance of the ion m/z is assigned to the corresponding amplitude band of a plurality of predetermined amplitude bands, producing a plurality of amplitude and m/z values for the each amplitude band. For each amplitude band of the plurality of predetermined amplitude bands, the plurality of amplitude and m/z values are combined into a peak, resulting in a plurality of peaks corresponding to the plurality of predetermined amplitude bands.
Abstract:
Systems and methods are provided for correcting uniform detector saturation of a mass analyzer using a calibration curve. In one method, a measured spectrum is received from a mass analyzer that includes a detector and an analog-to-digital converter (ADC) detector subsystem and that analyzes a beam of ions produced by an ion source that ionizes molecules of a sample using a processor. A total ion value of the measured spectrum is calculated by summing intensities of ions in the measured spectrum using the processor. A correction factor is determined by comparing the total ion value to a stored calibration curve that provides correction factors as a function of total ion values using the processor. Intensities of the measured spectrum are multiplied by the determined correction factor producing a corrected measured spectrum using the processor.
Abstract:
A precursor ion transmission window is moved in overlapping steps across a precursor ion mass range. The precursor ions transmitted at each overlapping step by the mass filter are fragmented or transmitted. Intensities or counts are detected for each of the one or more resulting product ions or precursor ions for each overlapping window that form mass spectrum data for each overlapping window. Each unique product ion detected is encoded in real-time during data acquisition. This encoding includes sums of counts or intensities of each unique ion detected the overlapping windows and positions of the windows associated with each sum. The encoding for each unique ion is stored in a memory device rather than the mass spectral data. A deblurring algorithm or numerical method is used to determine a precursor ion of each unique ion from the encoded data.
Abstract:
Each of one or more unknown compounds are separated from a sample over a separation time period. Separated compounds are ionized, producing one or more compound precursor ions for each of the unknown compounds and a plurality of background precursor ions. A precursor ion mass spectrum is measured for the combined compound and background precursor ions at each time step of a plurality of time steps spread across the separation time period, producing a plurality of precursor ion mass spectra. One or more background precursor ions are selected from the plurality of precursor ion mass spectra that have a resolving power in a range below a threshold expected resolving power. A separation time is detected for an unknown compound when a decrease in an intensity measurement of the selected background precursor ions over a time period exceeds a threshold decrease in intensity with respect to time.
Abstract:
The resolution of a TOF mass analyzer is maintained despite a loss of resolution in one or more channels of a multichannel ion detection system by selecting the highest resolution channels for qualitative analysis. Ion packets that impact a multichannel detector are converted into multiplied electrons and emitted from two or more segmented electrodes that correspond to impacts in different regions across a length of the detector. The electrons received by each electrode of the two or more segmented electrodes for each ion packet are converted into digital values in a channel of a multichannel digitizer, producing digital values for at least two or more channels Qualitative information about the ion packets is calculated using digital values of a predetermined subset of one or more channels of the at least two or more channels known to provide the highest resolution.
Abstract:
Two-channel electrical and photo-electrical TOF ion detection systems are provided. These systems maintain the resolution and dynamic range advantages of four-channel systems but at a lower cost. Electrodes or light pipes are configured to direct electrons or photons produced by ion impacts into two separate channels. The first channel receives electrons or photons resulting from the inner or central part of the rectangular pattern of each ion impact. The second channel receives electrons or photons resulting from the two outer ends of the rectangular pattern of each ion impact. In a two-channel digitizer, the first channel and the second channel are independently calibrated to align the first digital value and the second digital value in time and account for the convex shape of the ion impacts of each ion packet and/or the curvature of a microchannel plate.
Abstract:
Ions are separated from a sample over time and filtered. The precursor ions produced at each step are fragmented. Resulting product ions are analyzed using a mass analyzer, producing a product ion spectrum for each step of the transmission window and a plurality of product ion spectra for the mass range for the each scan. The plurality of product ion spectra are received, producing a plurality of multi-scan product ion spectra. At least one product ion is selected from the plurality of multi-scan product ion spectra that is present at least two or more times in product ion spectra from each of two or more scans. A known separation profile of a precursor ion is fit to intensities from the at least one product ion in the plurality of multi-scan product ion spectra to reconstruct a separation profile of a precursor ion of the at least one product ion.
Abstract:
An uncertainty weighted average of the equalized amounts of two or more quantifier ions is calculated from a quantitation experiment itself. n known i ions of a compound are mass analyzed over time in each of m different samples, producing n XIC peaks for each of the m samples. A reference ion j is selected that is a j ion of the n i ions or a hypothetical ion j. A ratio r(j,i) of a peak area of the j ion to a peak area of each ion of the n i ions is calculated for each of the m samples, producing m r(j,i) ratios for each of the n i ions. An expected ratio rq(j,i) is calculated for each ion of the n i ions from the m r(j,i) ratios for each of the n i ions. For each sample, the uncertainty weighted average is calculated using rq(j,i).
Abstract:
A precursor ion transmission window is moved in overlapping steps across a precursor ion mass range. The precursor ions transmitted at each overlapping step by the mass filter are fragmented or transmitted. Intensities or counts are detected for each of the one or more resulting product ions or precursor ions for each overlapping window that form mass spectrum data for each overlapping window. Each unique product ion detected is encoded in real-time during data acquisition. This encoding includes sums of counts or intensities of each unique ion detected the overlapping windows and positions of the windows associated with each sum. The encoding for each unique ion is stored in a memory device rather than the mass spectral data. A deblurring algorithm or numerical method is used to determine a precursor ion of each unique ion from the encoded data.