UV/VIS SPECTROPHOTOMETRIC STUDIES ON THE ANTILEUKEMIC AGENT GLYOXAL BIS(AMIDINOHYDRAZONE) [GLYOXAL BIS(GUANYLHYDRAZONE)]

Glyoxal bis(amidinohydrazone) (GBG) and several analogs thereof are compounds of considerable pharmacological interest, and a variety of HPLC and MECC methods have been developed for their analysis. In these methods, detection is invariably based on the strong UV absorption of the compound. Yet, almost nothing has been known of their UV and VIS spectral properties. In the present paper the UV and VIS spectroscopy of GBG has been studied in several solvent systems (water, 0.03 M aqueous sodium acetate buffer, 0.1 mM aqueous NaOH and dimethylsulfoxide). In the case of solutions in bare water, the shape of the UV spectrum depends drastically on concentration, probably because of changes in the species distribution of GBG as a function of concentration. The spectrum comprises one maximum at ca. 200 nm, and between ca. 250 nm and 400 nm an absorption region with distinctly higher absorbance. In the case of aqueous sodium acetate as well as NaOH solutions, one strong maximum can be detected (at ca. 285-288 nm and 332-337 nm, respectively). In both cases, the maximum occurs at constant wavelength, being independent of concentration. In dimethylsulfoxide, the spectrum of GBG contains an absorption band at distinctly higher wavelengths (lambda(max) 354 nm) than in any one of the aqueous solvents studied, indicating that solvent effects are considerable in the UV spectrum of GBG. In no case, distinct absorption could be detected at wavelengths higher than 400 nm. The results indicate that if aqueous media are used as eluents in HPLC analyses of bis(amidinohydrazones) or as solvents in direct UV analysis, they must be buffered.