A Recording Microfluorospectrophotometer

Abstract

A recording photoelectric microfluorospectrophotometer for very low light levels as encountered in tissue-autofluorescence was developed with special reference to detection and identification of cellular porphyrins. The instrument incorporates a tuned inductance-capacitance photomultiplier plate load in conjunction with chopper modulation of the exciting light at 976 cycles per second. The device is sensitive to much less than 10-10 gram of protoporphyrin and gives a satisfactory signal-to-noise ratio. Spectral resolution at 6400 A is less than 20 A. The spectrum from 5300 to 7030 A can be scanned in less than a minute.