High-speed characterization and analysis of orange oils with tandem-column stop-flow GC and time-of-flight MS

High-speed GC with time-of-flight (TOF) MS detection is used for the characterization and analysis of oils rendered from the peel of five diverse species of orange including bergemot orange, bitter orange, tangerine, mandarin orange, and sweet orange. With a user-defined signal-to-noise threshold of 100, 44 peaks were found and 36 compounds identified in the various oils. Some major constituent components show large concentration ranges over the five species. A 14-m-long, 0. 18-mm-i.d. column ensemble consisting of 7.0-m lengths of a trifluoropropylmethyl polysiloxane and a 5% phenyl dimethyl polysiloxane column was temperature-programmed at 50 degrees C/min starting at the time of injection to achieve analysis times under 140 s. The TOFMS was operated with a spectral acquisition rate of 25 spectra/s, and automated peak finding software successfully found all of the components, with the exception of one severely overlapping peak pair in bitter-orange oil. Of the 44 peaks, 25 were identified by use of a TOFMS library created for this study; another 11 were identified with a commercial terpene library, and 8 were not identified. A quantitative comparison (percent of total peak area) is presented for 16 components, which comprise 98.8-99.5% of the total peak area for the five orange species. Stop-flow operation of the column ensemble is used to enhance selectivity for targeted component pairs to facilitate single-channel detection for QA/ QC analysis of characterized samples and to enhance column selectivity for TOFMS characterization in cases in which peak overlap is so severe that only a single peak is observed.