A new detection technique for molecular spectrum, based on direct determination of light intensity absorbed, was developed, which is generally applicable to the determination of light-absorbing substances with the sensitivity as high as that of fluorometry. The quantitative formula of the method was reduced. It was demonstrated that spectra obtained by this method were similar to the corresponding absorption spectra. The analytical characteristics, such as sensitivity, detection limit, etc., were studied using absorbent materials in different ranges of wavelength and compared with both spectrophotometry and fluorometry.

Tetracyclinea ntibiotics could be degraded after being heated in boiling-water bath in alkaline solution (in KOH medium). The fluorescence excitation and emission wavelengths of the degradation products changed and the fluorescence intensity increased by 5-190 folds as compared with that of antibiotics themselves. It was considered that there occurred a nucleophilic ring rupture reaction to form the degradation products with lactonic structure. The interaction of the lone pair electrons of oxygen on the degradation products with the conjugated n electrons induced the increase of the delocalization for the conjugated electron system in the molecule and thus enhanced the fluorescence intensity.