Spectrofluorometer based on acousto-optic tunable filters for rapid scanning and multicomponent sample analyses.

Abstract

Advantages of the acousto-optic tunable filter (AOTF), namely its ability for fast scanning and multiple-wavelength diffraction, were exploited to develop a novel, all solid-state, nonmoving parts spectrofluorometer. This instrument is based on the use of two AOTFs: one for excitation and the other for emission. The first AOTF was used to specifically diffract white incident light into a specific wavelength(s) for excitation. Depending on the needs, the second AOTF (i.e., the emission AOTF) can be used as either a very fast dispersive device or a polychromator. In the first configuration, the sample was excited by a single-excitation wavelength; the emitted light was analyzed by the emission AOTF, which was scanned very fast. A speed of 4.8 A was found to be the fastest speed which the AOTF can be scanned with a reasonable S/N and resolution. With this speed, a spectrum of 150 nm can be measured in 312 microseconds. Faster scanning is possible but, because of the limitation due to the speed of the acoustic wave, may undesiredly lead to degradation in the S/N and spectral resolution. In the second configuration, both AOTFs were used as a polychromator. Several different rf signals were simultaneously applied into the first AOTF to provide multiple-excitation wavelengths. The emission was simultaneously analyzed at several wavelengths by the emission AOTF. With this configuration, the fluorometer can be used for the analysis of multicomponent samples, and the maximum number of components it can analyze is, in principle, a x b, where a and b are the number of excitation and emission wavelengths, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)