Impurity levels in the low parts-per-trillion (ppt) are possible to measure by atmospheric pressure ionization mass spectrometry. These impurity levels are achieved by the use of getter-based point-of-use purifiers for argon and nitrogen over a wide range of operating conditions, including room temperature operation. At these low impurity levels, the necessity for using ultraclean technology principles, such as all-metal construction, the elimination of dead zones, and the reduction of outgassing by the use of techniques such as oxygen passivation, is clearly demonstrated, especially to achieve moisture levels near the 100 ppt range.