Integrated Analysis of GC-HRTOFMS Data Using Hard and Soft Ionization to Identify Trace Impurities in Fine Chemicals
Gas chromatography combined with mass spectrometry (GC-MS) is well known as a powerful analytical tool for non-targeted analysis of complex mixtures such as environmental samples, quality control for feedstocks and fine chemicals, contaminants and impurities in commercial products, and metabolomic studies. GC-MS with a pyrolysis inlet is also widely used for materials characterization.
Interpretation of GC-MS data is heavily reliant upon searching electron ionization (EI) mass spectra against databases such as the NIST and Wiley mass spectral databases. Problems arise if the molecular ion is weak or absent, making it difficult to discriminate between compounds with different compositions, but similar mass spectra. A further complication is that many compounds do not have an entry in the databases.
A high-resolution time-of-flight mass spectrometer (HRTOFMS) is ideal for non-targeted analysis because it provides accurate mass and isotope data and is compatible with fast chromatography. Soft ionization methods such as chemical ionization (CI), field ionization (FI) and photoionization (PI) provide molecular weight and elemental composition data to complement the database search results for electron ionization. Manual interpretation of the data is time-consuming. Here, we present a simple example of how an automated data interpretation program (“msFineAnalysis”) combines all of the information from the high-resolution mass spectra for both electron ionization and chemical ionization mass spectra to identify trace impurities in triphenylphosphine (1), a fine chemical used as a reagent for organic synthesis.
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