A methodology has been developed which provides a means of detecting and chemically characterizing low levels of contaminants in process gases used in the microelectronics industry. NVR monitors based on SAW (surface acoustical wave) technology were exposed to cylinders of a common gas used in microelectronics applications. A control cylinder of clean N2 was compared with a deliberately contaminated cylinder and two supposedly clean cylinders from different suppliers. The SAW devices were able to detect the residue deposited from each gas. After exposure to the cylinders, the SAW devices were directly analyzed by time-of-flight secondary ion mass spectrometry (TOF-SIMS) to identify the deposited residues. The TOF-SIMS instrument was equipped with a liquid-N2 cooled sample stage to facilitate detection of semivolatile species in the UHV environment necessary for the analysis.