Ultrahigh sensitivity chiral HPLC analysis of nonfluorescent cyclodimers of 2-anthracenecarboxylic acid (AC) was achieved with much improved accuracy and reproducibility through a nonconventional on-detector photoreversion/re-excitation/detection mechanism. Excitation of cyclodimers at 254 nm in the detector cuvette caused photoreversion to AC, in situ excitation of which led to strong fluorescence at longer lambda. The sensitivity was enhanced by a factor of ca. 2000 compared to usual UV detection.