A method for simultaneous determination of nitrogen and oxygen isotope compositions of natural nitrate and nitrite, which quantitatively converts natural nitrate and nitrite into an organic ester and a nitro-compounds respectively, and then nitrate and nitrite δ.sup.18O and δ.sup.15N are simultaneously determined by adopting a gas chromatography/pyrolysis/gas chromatography/isotope ratio mass spectrometry coupling technology (GC/Py/GC/IRMS). According to the method for simultaneously determining the nitrogen and oxygen isotope compositions of the natural nitrate salt and nitrite salt, the small amount of sample does not result in the loss, acquisition, exchange and fractionation of nitrogen and oxygen.

A compound is separated or introduced from a sample at a plurality of different times. The compound is ionized, producing an ion beam. The compound is selected and mass analyzed or the compound is selected, fragmented, and fragments of the compound are analyzed from the ion beam at the plurality of different times, producing a plurality of mass spectra. An XIC is calculated for the compound using the plurality of mass spectra. A chemical structure of the compound received in notation form is converted to a numerical vector using a processing algorithm operable to convert the notation form to the numerical vector. A plurality of peak shape parameters is calculated for the compound using the numerical vector and a machine trained model. A peak of the XIC is identified as a peak of the compound using the plurality of peak shape parameters and optionally a peak integration algorithm.

Exemplary embodiments provide computer-implemented methods, mediums, and apparatuses configured to perform targeted isotope clustering. A mass spectrum for a sample may be obtained from an analytical laboratory instrument, and a set of peaks within the mass spectrum may be identified. A list of fragments expected to be potentially present in the sample may be obtained, and a set of predicted peaks may be generated from the list. The spectrum may be searched for the predicted peaks to determine if any combination of the peaks present in the spectrum match the expected fragment patterns. Accordingly, isotope (charge) clusters may be built in a targeted way using a priori knowledge to target the matches. As a result, spectrum analysis can be done more quickly and efficiently than in conventional systems that use neutral or untargeted matching, and the matches can be made more accurately.

Methods for identifying viral protein constituents and quantifying the relative abundance of such viral protein constituents in a sample of viral particles are disclosed. In embodiments, the methods include first-dimension chromatography to separate intact viral capsid components of the sample, online denaturation of the viral capsid components to produce intact viral proteins, second-dimension chromatography to separate the viral proteins, and mass spectrometry to determine the masses of the viral proteins and identify the viral protein constituents of the sample.

A method for multiple transition monitoring using a liquid chromatography mass spectrometry device is disclosed and comprises determining at least one data set from at least one data base, the data set comprising at least one reference measurement of at least one transition of at least one analyte with the liquid chromatography mass spectrometry device; determining at least one reference peak information of the transition of the analyte using an initial setting of a measurement window, wherein the measurement window is defined by a time frame of retention times; determining an actual setting of the measurement window considering the reference peak information, wherein the determining comprises adjusting the time frame; measuring the transition of the analyte with the liquid chromatography mass spectrometry device and determining a measured peak information of the transition of the analyte using the actual setting of the measurement window.

A confirmation ion ratio allowable value calculation unit calculates a confirmation ion ratio allowable value when a target ion and confirmation ions are interchanged based on a preset confirmation ion ratio allowable value, and a peak identification processing unit identifies mass peaks of the target ion and the confirmation ions based on the confirmation ion ratio allowable value. A peak waveform processing unit calculates peak areas of the target ion and the confirmation ions, and a calibration curve creation unit creates calibration curves for quantification based on the target ion and the confirmation ions from a peak area of a target compound included in a standard sample. A quantitative value calculation unit obtains quantitative values while referring to a calibration curve corresponding to a peak area for a target compound included in an unknown sample. A quantitative analysis result display processing unit displays the quantitative values and chromatogram peak waveforms.

A mass spectrometer includes: a target compound input receiving section for receiving an input of one or more target compounds; a measurement execution section for reading MRM measurement conditions, including a plurality of MRM transitions, respectively corresponding to the one or more target compounds from a storage section, and measuring the sample under the MRM measurement conditions; a measured multi-MRM spectrum creation section for creating a measured multi-MRM spectrum indicating an intensity of product ions as a mass peak on a graph having mass-to-charge ratios of the product ions on one axis, the intensity of the product ions acquired by measuring the sample; and a similarity degree calculation section for obtaining for each of the target compounds, a degree of similarity between standard multi-MRM spectrum stored in the storage section and the measured multi-MRM spectrum.

The disclosure describes a method for simultaneous determination of nitrogen and oxygen isotope compositions of natural nitrate and nitrite, which quantitatively converts natural nitrate and nitrite into an organic ester and a nitro-compounds respectively, and then nitrate and nitrite δ.sup.18O and δ.sup.15N are simultaneously determined by adopting a gas chromatography/pyrolysis/gas chromatography/isotope ratio mass spectrometry coupling technology (GC/Py/GC/IRMS). According to the method for simultaneously determining the nitrogen and oxygen isotope compositions of the natural nitrate salt and nitrite salt, the small amount of sample does not result in the loss, acquisition, exchange and fractionation of nitrogen and oxygen.

The method according to the present invention includes: a training sample measurement process (S1, S2) in which, for a food product belonging to the same kind as a determination target, a plurality of training samples individually labeled with a known state of quality are subjected to a measurement using a chromatograph mass spectrometer under the same analysis condition; a training sample data collection process (S3, S4) in which an index value related to the magnitude of a peak observed on an extracted ion chromatogram obtained by the measurement is acquired for each training sample, and the index value of the peak at each retention time common to the training samples is extracted; and a discrimination model creation process (S5-S7) in which a supervised training is performed to create a discrimination model, using, as the training data, the index value of the peak at each retention time common to the training samples acquired for each of the labeled training samples. Measurement data for an unknown sample is inputted into a discriminator based on the discrimination model, to obtain a quality discrimination result.

A method for relative quantification of organic and biological compounds by electrochemical mass spectrometry is disclosed. The method involves using electrochemistry (EC) in a mass spectrometry (MS)-based relative quantitative analysis. In this method, isotope-labeled standards or running calibration curves are not employed. A quantification method could include the steps of subjecting a sample analyte to liquid chromatography or electrophoresis separation, followed by an electrochemical oxidation or reduction in an electrochemical cell, and then mass spectrometric detection.