A phenytoin derivative represented by formula (I) ##STR1## wherein Ph denotes a phenyl group, X denotes --O--, --NH-- or --CH.sub.2 --, Y denotes --CO-- or --CH.sub.2 --, Z denotes a hydrogen atom or a hydroxyl group, M denotes a salt-forming cation, and m and n are each an integer of 0 to 8 and m+n is at least 2. Said compound is useful to produce a phenytoin-labelled DNA or RNA probe. When using such a probe, DNA or RNA in the specimen can be detected with high sensitivity.
A method and apparatus for performing a chemiluminescent assay are disclosed. A test sample or multiple test samples is or are deposited on a supporting matrix and chemiluminescence of the sample(s) is effectuated. Low energy chemiluminescence emitted during chemiluminescence is removed by a light attenuation optical filter. Chemiluminescence is detected from the filtered light using a light detector means and chemiluminescence is counted using a chemiluminescence counter coupled to the light detector means.
