Mass spectrometry (MS) identification algorithm

Inventors

Sadowski, Charles S. • Andersson, Greger • Judge, Kevin

Assignees

Smiths Detection Inc

Abstract

A system includes a gas chromatograph configured to determine experimental chromatographic data including retention times associated with samples. The system also includes a mass spectrometer configured to determine experimental mass spectral data associated with samples. The mass spectrometer can include a quadrupole field ion trap that uses a non-classical detection technique. The system determines a retention index for an unknown sample based upon retention times for a calibration sample and the unknown sample, and identifies reference mass spectral data using the retention index. The reference mass spectral data can include spectra measured using a classical detection technique. The system can compare the experimental mass spectral data to the reference mass spectral data using one or more comparison metrics, such as a percent fragment match and/or a variance match. A score can be determined to identify the unknown sample using one or more of the metrics.

Core Innovation

An invention is directed to a GC-MS identification algorithm and a corresponding GC-MS system for identifying an unknown sample. The approach determines experimental chromatographic data comprising a first retention time associated with a calibration sample and a second retention time associated with the unknown sample. Using the first retention time and a retention time recorded for the calibration sample in an electronic database comprising reference mass spectral data, the controller determines a retention index for the unknown sample and adjusts the second retention time based on the retention index.

The controller filters the electronic database comprising reference mass spectral data using the retention index determined for the unknown sample to identify a subset of a plurality of database entries. At least one database entry in the subset comprises mass spectral data measured using a quadrupole mass spectrometer. The system then determines experimental mass spectral data for the unknown sample using a toroidal ion trap mass spectrometer, and compares the experimental mass spectral data to the filtered subset of database entries to identify the unknown sample.

The comparison includes matching the experimental mass spectral data for the unknown sample to at least one database entry in the filtered subset based upon detecting, by the toroidal ion trap mass spectrometer, at least one of a first mass fragment having a mass equal to the molecular weight of the unknown sample plus a value of one, a second mass fragment having a mass equal to two times the molecular weight of the unknown sample plus a value of one, or a third mass fragment with a neutral molecule. The identification can be performed using matching comparison metrics such as percent fragment match and variance match, including an optional weighted combination to compute a hit score.

Claims Coverage

The document provides three independent claims: a GC-MS system, a method, and a non-transitory computer-readable storage medium. Across the independent claims, the inventive features center on retention-index-based filtering of an electronic reference database and toroidal ion trap fragment-chemistry-based matching to identify an unknown sample, with matching optionally based on percent fragment match and/or variance match.

Across the independent claims, identification of an unknown sample is achieved by determining a retention index from calibration retention information and electronic database retention times, filtering the electronic reference database accordingly, and matching toroidal ion trap experimental mass spectral data to the filtered database subset based on detection of molecular-weight-related fragments (molecular-weight±one, 2×molecular-weight±one, or neutral-molecule fragments), with identification comparison optionally based on percent fragment match and/or variance match.

Stated Advantages

Documented Applications