sCLIPS™ (self Calibrating Line-shape Isotope Profile Search) enables users of accurate mass instruments including TOF, high resolution quadrupoles, Orbitrap, magnetic sector, and FT-ICR MS to dramatically improve formula ID through Spectral Accuracy without the need to run calibration standards. The patented sCLIPS approach utilizes the fully resolved monoisotopic peak from high resolution instruments to create a line-shape TrueCal™ calibration that is applied to the entire isotope profile of the ion of interest. This enables exact isotope modeling when comparing the MS response of an unknown ion against the true mass spectra (theoretically calculated responses) for all possible candidate formulas and allows spectral differences as small as 0.1% to be measured, leading to formula ID. One of the benefits of the approach is that it requires no known calibration ions, and instead utilizes the fully resolved monoisotopic peak of the unknown ion itself for the sCLIPS line-shape calibration.
The flow diagram below illustrates the steps performed with sCLIPS. For sCLIPS to perform properly, the monoisotopic peak must be fully resolved from the A+1 isotope peak, a level of resolving power easily achieved by higher resolution systems for singly charged small molecule compounds (m/z < 1,000). It is important to note that sCLIPS does not calibrate for or improve mass accuracy, which is required by CLIPS on low resolution MS, but only calibrates the line-shape while preserving the same (high) mass accuracy of the high resolution MS. However, the line-shape calibration is near perfect since the monoisotopic peak is as close as practical in mass and measurement time to the other isotope peaks.
sCLIPS in included in MassWorks Premium.
Ideal for high resolution instruments (e.g. TOF, Orbitrap, FT-ICR)
- No calibration compounds necessary
- The mono-isotopic peak of unknown as the TrueCal standard
- Unique, patented self-calibration
- Mathematically exact isotope modeling
- ≥ 99% Spectral Accuracy achievable on well designed and operated systems
- Going beyond mass accuracy alone for formula ID
- Capable of eliminating up to 95-99% of incorrect formulas
- Powerful mixture analysis with un-resolved MS signals
For an example application using an Orbitrap instrument see:
Spectral accuracy of molecular ions in an LTQ/Orbitrap mass spectrometer and implications for elemental composition determination JASM 2009