Abstract: Analytical reagents designated "release tags", for labeling molecular species with a highly detectable signal group which can be released in the form of a volatile compound at a desired point in an analytical procedure. In one embodiment, the release tags have the formula(SgCo).sub.x L(Rx).sub.rwherein each Sg is a signal group bearing one or more electronegative substituents, L is any of a wide variety of groups which when attached to a carbonyl group form a readily cleaved linkage, each COL moiety is a release group which upon scission releases signal group Sg in the form of a volative compound, and each Rx is a reactivity group for attaching the release tag compound to a molecular species to be labeled. In a second embodiment, the release tags have the formulaSgReRxwherein Sg and Rx are defined as above and Re is a release group which is an olefin, .alpha.-hydroxy ketone or vicinal diol. Conjugates of the release tag compounds and assay methods employing them are also disclosed.