STUDY ON SENSITIZED PHOTOCHEMICAL FLUORESCENCE OF MENADIONE SODIUM BISULFITE AND ITS APPLICATION IN PHARMACEUTICS ANALYSIS

Menadione sodium bisulfite (MSB), vitamin K-3, a non-fluorescent compo und, was converted into an intensive fluorescent compound (lambda(ex)/ lambda(em)=340 nm/465 nm) on irradiation with ultraviolet radiation in an anaerobic alkaline medium, and acetone showed a strong sensitizing effect on this photochemical reaction when the radiation used was abs orbed by acetone. The reaction rate increased as the concentration of acetone increased, the maxima of the fluorescence spectra, however, re mained unchanged. The sensitized photochemical reaction was assumed to begin with the absorption of photons by acetone and a triplet-triplet energy transfer process was proposed for the sensitizing mechanism, i n which acetone acted as an energy donor, and MSB as an energy accepto r. A new in situ photochemical fluorimetric method was consequently pr oposed for the determination of MSB. The solutions were pumped through a PTFE mixing-tube and then stopped and kept in an 18 mu l flow cell where the photochemical reaction took place in situ on irradiation for 120 s (with an excitation wavelength, lambda(ex), 280 nm, excitation slit, EX, 7 nm), and then lambda(ex) was changed from 280 to 340 nm pr omptly to measure the fluorescence intensity of the photochemical prod uct at 465 nm. Na2SO3 was used as the deoxygenation reagent. The calib ration graph was linear up to 1.1 mu g ml(-1) MSB (r=0.999), and the l imit of detection (LOD) was 0.76 ng ml(-1). The coefficients of variat ion were 1.0% (n=6) and 0.99% (n=6) for 0.44 and 1.1 mu g ml(-1) MSB, respectively. Its application to the analyses of vitamin injections an d urine samples was satisfactory, and the recovery of vitamin K-3 in u rine was 92-94%. The kinetic behavior of this reaction and the effects of some experimental conditions as well as the mechanism for the sens itization by acetone were investigated and discussed in detail.