Digital parallel acquisition in frequency domain fluorimetry

Abstract

The analog electronics commonly found in frequency domain fluorometers are limited to collecting only a single frequency at a time, and can be a source of systematic errors. We have developed an instrument in which most of the analog electronics are replaced with a computer-controlled digital-acquisition system. The computer is used for the direct collection of multifrequency data; filtering and calculation of the phase and modulation ratio are done by the software. From these values, fluorescence lifetimes can be determined. This new approach reduces most of the systematic errors due to the analog electronics’ hardware and allows for reconfiguration of the instrument with only minor changes of the software. This digital-acquisition system is not a simple substitution of an analog element, but it provides a new function and new capabilities for frequency domain fluorometers. We have used this digital approach to build a ‘‘parallel’’ phase fluorometer which simultaneously collects and processes several modulation frequencies.