System and method for background removal in spectrometry system
An analysis system includes a separation system that provides compounds to a sample cell of a spectrometric system. The system analyzes spectral information from the spectrometric system by optimizing retention windows for the compounds and identifies quantities of the compounds by comparing spectral information within and outside the respective retention windows.
1. A method for analyzing sample spectra of a sample from a spectrometric system, the method comprising:
obtaining the sample infrared spectra of compounds eluting from a separator with the spectrometric system that gathers the sample infrared spectra by flowing the compounds into a gas cell;
shifting entire retention windows to find a rough approximation of the retention windows and then separately shifting lower bounds of the retention windows and shifting upper bounds to fine tune the retention windows;
comparing the sample infrared spectra from the shifted retention windows to optical reference spectra for compounds of interest in the sample by regressing the optical reference spectra over the sample infrared spectra of the shifted retention windows and rating fit; and
updating the retention windows used to analyze the sample with the shifted retention windows with the best fit.
2. The method of claim 1 , further comprising validating the shifted retention windows.
3. The method of claim 2 , wherein validating the shifted retention windows comprises:
calculating retention times for compounds based on the shifted retention windows;
comparing the calculated retention times against expected retention times for the compounds; and
analyzing differences between the calculated retention times against expected retention times for different compounds to validate the shifted retention windows.
4. The method of claim 2 , wherein validating the shifted retention windows comprises:
calculating retention times for compounds based on the shifted retention windows;
comparing the calculated retention times against expected retention times for the compounds; and
analyzing differences between the calculated retention times against expected retention times for different compounds to highlight outlier calculated retention windows.
5. The method of claim 1 , wherein the sample spectra are gathered by a Fourier transform infrared spectrometry (FTIR) system.
6. The method of claim 1 , wherein shifting the retention windows includes moving the retention windows to several different locations in time around a baseline window location.
7. The method of claim 6 , wherein comparing the sample spectra comprises calculating regressions using a reference optical spectrum for a compound of interest against the sample spectra while performing background removal.
8. The method of claim 7 , wherein fit of the reference optical spectrum is rated based on a fit between the reference optical spectrum and the sample spectra for the different locations around the baseline window location.
9. The method of claim 8 , further comprising penalizing the fit for each window if a concentration of the compound of interest has a negative concentration.
10. The method of claim 1 , wherein comparing the sample spectra comprises regressing the reference spectra over a quant spectrum selected from the sample spectra from the shifted retention windows and rating fit.
11. The method of claim 1 , wherein sample spectra from the updated retention windows are used in a background removal process.