Salmonella typhimurium was determined with the use of a combination of an enzyme-linked inmmunosorbent assay (ELISA), a phosphatase mediated end step, and a hand-held ion mobility spectrometer for detecting phenol, the ELISA reaction product. Elevated temperature and low solution pH improved the efficiency for thermal desorption of phenol from filter paper strips; still, the thermal desorption profile was broad and ocfjcurred over a 2-3.5-min range. As a result, the detection limits were restricted to ฯณ10 4 bacteria in 10-l aliquots of sample. Precision of quantitative response with a hand-held ion mobility spectrometry (IMS) analyzer ranged from 0.7%-42% relative standard deviation (RSD) for of phenol, and the precision mean was 0-10 g 12% RSD. Thermal and hydrolytic stability of phenylphosphate, the substrate for ELISA reactions, was excellent in buffer solution, without detectable degradation for over 60 days at temperatures from ุ70 to Re-45 ุC. sponse to increasing levels of S. typhimurium antigen by IMS correlated with a traditional optical spectrophotometric method and showed comparable detection limits. Calculations portend a 100-fold improvement in detection limits through only improved engineering of an ELISA-IMS interface.