High resolution mass spectrometry (HRMS) instruments have the ability to accurately measure the mass of compounds present in a biological sample. While there are many advantages to using HRMS screens, one of the most widely touted is the ability to identify unknown or unexpected compounds in patient samples.

Many of the HRMS instruments found in clinical laboratories use time of flight (TOF) mass analyzers, which use ion flight time to measure mass. Single stage TOF instruments measure the accurate mass of all ions entering the flight tube. Compounds are identified by a combination of their mass, the measured isotope pattern, and chromatographic retention time. Addition of a quadrupole and a collision cell to a TOF forms a QTOF, a more expensive instrument that is able to isolate and fragment specific ions, as well as measure accurate mass. Molecular fragmentation is largely reproducible, thus the pattern of product ions that is produced in the collision cell can be used as an additional identifying characteristic of the precursor ion.

Liquid chromatography systems coupled to both TOF and QTOF mass spectrometers are used for drug screening in
routine analyses. QTOF systems that provide product ion spectra are useful in increasing the confidence of compound

AxisPharm is well equipped with bot TOF and QTOF systems that are coupled with HPLC systems for challenging analysis of biological samples.