Methods and apparatuses for highly sensitive detection of analytes using redox reactions. A library of heat reactions of analytes of interest with a variety of catalysts at a variety of temperatures is prepared. An array of sensors with low thermal mass heating elements is prepared, depositing the same or different catalysts, such as metal oxide catalysts that have multiple oxidation states, on each heating element. The low thermal mass heating elements are preferably not in thermal contact with a substrate, or a low mass substrate is used. The array is exposed to a sample at various temperatures. The sign and magnitude of the heat effect of the redox reaction of compounds in the sample or their decomposition products with each catalyst is measured and compared with the library. The catalysts and temperatures are chosen so that the desired analytes have a unique pattern of heat effect signs and magnitudes when reacted with those catalysts at those temperatures. The resulting detector is highly selective and sensitive to the analytes of interest.