High-performance liquid chromatographic detector based on near-infrared semiconductor laser fluorimetry

Three polymethine dyes, which fluoresce at 780–820 nm, are separated by reversed-phase chromatography and detected fluorimetrically with a semiconductor laser for excitation. The detection limit for anhydro-3,3,3′,3′-tetramethyl-1,1′-bis(4-sulfomethyl)-4,5,4′,5′-dibenzoindotricarbocyanine hydroxide (sodium salt) is 0.3 pg, which is almost three orders of magnitude better than the value obtained by conventional fluorimetry.