Do not use the air and water check described below if you have recently vented the MSD. It can take up to 4 hours for the abundance of m/z 28 (nitrogen) to fall to an appropriate level. It can take up to 24 hours for the abundance of m/z 18 (water) to fall to an appropriate level.
Compare the abundances of m/z 28 (nitrogen) and m/z 18 (water). The abundance of m/z 28 should be less than the abundance of m/z 18.
Compare the abundances of m/z 18 (water) and m/z 69 (PFTBA). The abundance of m/z 18 should be less than 10% of the abundance of m/z 69.
Compare the abundances of m/z 28 (nitrogen) and m/z 69 (PFTBA). The abundance of m/z 28 should be less than 5% of the abundance of m/z 69.
Compare the abundances of m/z 28 (nitrogen) and m/z 32 (oxygen). If an air leak is present, the ratio of m/z 28 to m/z 32 will be about 5:1. If the abundance of m/z 28 is well over 5 times the abundance of m/z 32, then there may be another chemical present with an ion at m/z 28 such as CO or C2H4. If CO is present, there is typically a large peak at m/z 44 (CO2) also.
If the air and water check confirms an air leak, see:
If you have difficult finding a leak, use the following procedure: