Multifiber, multiwavelength, fiber optic fluorescence spectrophotometer

A fibreoptic spectrofluorimeter capable of remote operation of up to 18 biosensors under fully automated, multiplexed control was constructed. Excitation and emission wavelengths were separately adjustable, as were optical bandwidths, signal gain, phase, integration time, and illumination duty cycle. Synchronous demodulation was used to enhance signal-to-noise ratio and allow operation under ambient lighting conditions. Detection limit for aqueous sodium-fluorescein was below 1 ng/mL at greater than unity signal-to-noise ratio, with effective sampling volumes less than 0.02 mu L. The fluorimeter showed characteristic fiberoptic sampling behavior with asymptotic nonzero signal magnitudes under increasing path-length conditions.