Ultra-sensitive time-resolved nanoliter volume fluorometry based on UV LEDs and a channel photomultiplier tube

摘要

A capillary fluorometer was constructed using a 2 mW, 365 nm ultraviolet (UV) light emitting diode (LED) as the excitation source and a new-generation high-gain (3x10~8) channel photomultiplier tube. The use of a LED permitted rapid pulsing of the excitation source so that the instrument could be employed for time-resolved fluorescence (TRF) applications. A detection limit of ～2x10~8 molecules of BHHT (4,4'-bis (1",1",1",2",2",3",3"-heptafluoro-4",6"-hexanedion-6"yl)-o-tephenyl)-Eu (III) were resolved within a 1.25 nanoliter volume at a S/N ratio of 3:1. Ultimate sensitivity of the system was compromised due to visible luminescence emitted by the UV LED, centred around 550 nm extending to > 700 nm and 2nd-order exponentially decaying with lifetimes of 40 μs and 490 μs.