Scheibner O, Bromirski M. Application Note 573 Productivity of a liquid chromatograph-mass spectrometer (LC-MS) system is measured in samples per day. To achieve higher productivity, modern ultra high-performance LC-MS (UHPLC-MS) methods use very short gradients. Chromatographic peak widths are often below 5 seconds at the base. A high-resolution, accurate-mass (HR/AM) mass spectrometer operating in full-scan mode must be able to provide a sufficient number of scans (≥10) across the chromatographic peak without compromising sensitivity and selectivity. As reported earlier, a resolving power in excess of 50,000 (FWHM at m/z 200) combined with a mass extraction window of 5 ppm is necessary to ensure selectivity comparable to established MS/MS techniques.
The Thermo Scientific™ Exactive™ Plus Orbitrap mass spectrometer (Figure 1) is the second generation of the Exactive product family. It features two major changes over the first generation instrument. First, in the ion optics the tube-lens / skimmer assembly has been replaced by an S-Lens (Figure 2) that provides significantly higher ion transmission, increasing the instrument’s sensitivity. Second, the Orbitrap mass analyzer and related electronics have been improved, resulting in higher scan speed and resolution, as well as improved polarity switching. As a result, the range of resolving power is from 17,500 to 140,000 at m/z 200, with a maximum scan rate of 12 Hz.
In this research, the Exactive Plus instrument was used to analyze extracts of horse feed spiked with common pesticides.