The upper pressure limit of a partial pressure analyzer (PPA) was extended by differential pumping so that gas composition of process pressures are evaluated. The selection of orifice size for differential pumping, first by calculation, then by empirical data, is presented. The range of a linear relation for reduced total pressure vs. process pressures in the millitorr range for several gases is presented. The validity for scans of multiple gas species for 0 – 130 amu was also evaluated by testing, comparing scans in the high pressure region to those in the reduced pressure region. The application of this method for an autoresonant ion trap will be presented for the first time in this pressure reduction protocol as it provides measurement of fast transients at these higher pressures. Trade-offs for orifice sizes and pressure reduction ratios will be discussed. The test set-up as it relates to the AVS Recommended Practices and the conclusions for pressure ranges that it provides will be given.