Autotune adjusts all MS parameters to predetermined target values. It finds the mass peaks, obtains adequate response and resolution, optimizes the response of 3 masses, optimizes response and resolution of other masses, and obtains accurate mass assignments.
You will need to autotune when the MS system is first set up, when the acquisition software is reinstalled or upgraded, and when maintenance is performed on the MS.
PFTBA (perfluorotributylamine) is used as the tuning compound for all GC/MS EI mode autotunes. Autotune in EI mode typically uses masses 69, 219, and 502 to adjust parameters on the analyzer elements. Any ions in PFTBA are acceptable (if the abundance is sufficient) to use with tuning. Thus the MS may be tuned to optimize for specific ions.
The resulting parameters from an autotune or quick tune are saved in a tune log file.