A new organ spectrophotometer for sensitive dual-wavelength absorbance measurement and spectral scanning of intact perfused organs.

1. A new spectrophotometer was designed and constructed for application in high sensitivity dual-wavelength absorbance and fluorescence measurement and spectral scanning (non corrected) from intact perfused organs, combining advantages of other instruments described in the literature. 2) The time-sharing principle was applied to gain high stability. All optical and electronic components except the light paths of the wavelength modulation system are common to both wave-lengths. For this purpose the logarithmic stage was introduced before demodulation. Stability is about 0.001 A/h and noise about 0.001 A. 3) The performance of the instrument with a biological object, the isolated perfused rat liver, is demonstrated in the dual-wavelength mode and in the spectral scanning mode. Limitations in stability and in time resolution in such an application result from the properties of the biological object, not from the instrument.