A new approach to enhancing the performance of formula identification of true unknowns beyond high mass and spectral accuracy was evaluated. Three heuristic rules on upper limits and ratios of elements were tested for their effectiveness in filtering out false positive formulas with both high- and low-resolution mass spectrometry data. The rule on elements' upper limits was found to be the most effective one in eliminating incorrect formulas.
A novel method that significantly improves the accuracy and reliability of "unknown" compound identification for volatile organic compounds by GC-MS is described.
With electron ionization (EI) used in most gas chromatography–mass spectrometry (GC–MS) applications, the molecular ion typically is broken apart into multiple fragment ions during the EI process.