Spectral skewing in gas chromatography-mass spectrometry: Misconceptions and realities.

In the field of gas chromatography-mass spectrometry, linear quadrupole instruments remain the most popular. Quadrupole mass spectrometers are scanning instruments. It means that ions with different m/z values pass through the quadrupole sequentially. When analyte concentration changes during scan period, recorded mass spectrum is distorted. This phenomenon is called spectral skewing. There are two misconceptions associated with the spectral skewing: (1) the spectral skewing can affect the results of library search; (2) bilinear chemometric methods are often applied to skewed (distorted) GC/MS data to perform automatic data processing. We attempt to clarify these misconceptions. We can conclude that even strong distortion of mass spectrum (caused by the spectral skewing) practically does not change efficiency of automatic search against mass spectral database. On the other hand, even minor distortion of data (caused by the spectral skewing) can significantly distort results of automatic data processing (especially in the case of minor components). Interactive Excel files (presented in Supplementary material) illustrate our findings.