Accurate Mass

Accurate Mass uses High Resolution Mass Spectrometry to determine the molecular weight of a sample to within 5 ppm or accurate to the third decimal place. It is used to verify a predicted molecular formula and isotope pattern of a pure compound.

  • This service is primarily performed on the Agilent 6230 ESI-TOF, using either the ESI or DART ionization modes.
  • For masses greater than 1000 Da, higher resolving power is required to maintain the necessary mass accuracy. The Bruker Impact II QqTOF performs these services for large molecules still compatible with ESI.
  • Very large molecules, such as polymers, proteins, and oliogmers, that are not compatible with ESI can be analyzed by MALDI instead. Using the Bruker AutoFlex MALDI-TOF, accurate mass can be performed, with the trade-off of lower acceptable mass accuracy. If 5 ppm mass accuracy is still desired from MALDI data, an internal standard in the sample/spot is required.
    • Internal standards are generally isotopically labeled standards of similar compound type, class, or structure. Non-isotopically labeled standards are also acceptable so long as there is no mass overlap of the standard with the sample.
  • For small molecule (< 1000 Da) volatile compounds not compatible with ESI or DART ionization, the Thermo Scientific Exploris GC-MS Orbitrap can be used via direct insertion probe (DIP).