Development of a Novel Fluorimeter Based on Superluminescent Light-Emitting Diodes and Acousto-Optic Tunable Filter and its Application in the Determination of Chlorophylls a and b

Abstract

A novel, compact, inexpensive fluorimeter that has high sensitivity and no moving parts has been developed by using super luminescent (bright-blue) light-emitting diodes (SLEDs) and an acousto-optic tunable filter (AOTF). In this instrument, the recently developed gallium nitride SLEDs were used in a counterpropagating configuration to provide excitation light. These SLEDs provide not only high intensity (several milliwatts) but also wide spectral bandwidth in the blue region (from 370 to 570 nm). The AOTF can be placed before the sample to facilitate the measurements of excitation spectra or after the sample for the emission spectra measurements. This fluorimeter is suitable for the sensitive and general fluorescent analysis of a variety of compounds. It has been used, as an example, for the sensitive and simultaneous determination of chlorophylls a and b. Detection limits of 2.30 × 10⁻⁹ and 1.10 × 10⁻⁹ M have been achieved for chlorophyll a and chlorophyll b, respectively. Index Headings: Superluminescent light-emitting diode; Acousto-optic tunable filter; Fluorescence; Chlorophyll.