Yoctomole

A low cost, 0.75-mW helium neon laser, operating in the green region at 534.5 nm, is used to excite fluorescence from tetramethylrhodamine isothiocyanate-labelled DNA fragments that have been separated by capillary gel electrophoresis.The detection limit (3σ) for the dye is 500 ymol [1 yoctomole (1 ymol) = 10⁻²⁴ mol] or 300 analyte molecules in capillary zone electrophoresis