ULTRAVIOLET SPECTRAL FEATURES AFFECTING COMPUTER-AIDED MULTIWAVELENGTH QUANTITATION OF MULTICOMPONENT MIXTURES USING PHENOTHIAZINES AS MODEL

Modern quantitation of multicomponent mixtures with ultraviolet spectr oscopy is tending towards application of computer-aided calculations w here mathematical overdetermination has been favored for reducing rand om errors in such analysis. Application of this procedure has however been made difficult by the observation of anomalous results. Additiona l sources of error is reported in the present study. Error patterns we re traced to features of the spectra of components of the standards ra ther than the spectra of the mixtures to be analyzed alone. Calculatio n efficiency correlated inversely with isoabsorptive points of the sta ndard spectra in the calibration matrix. New computational indices, re lative total absorptivity and relative total absorbance, (RTA), calcul ated by the integration of absorption spectra of the components was sh own to be a measurement that could be employed to optimize limit of qu antitation of components present at low levels. RTA could be optimized separately for each component and could be a useful tool in automatic weighting factor allocation in future multicomponent analysis routine s. Mixtures of chlorpromazine (CPZ) and its sulfoxide (CPZSO) which is of medical, forensic and industrial interest has been chosen as a mod el in this study. The optimized wavelength range for analysis of CPZ-C PZSO was determined to be 270-360 nm.