STUDIES ON MULTICOMPONENT SPECTROSCOPIC ANALYSIS OF DYE SOLUTIONS

Absorbance measurements of dyes in solution are used in dye characterization, in setting up dyeing recipes, or in monitoring the progress of dyeing processes. Multicomponent spectroscopic analysis of dye solutions was performed in this research. The spectra of a set of dye solutions which contained either three or four different dye components were recorded. Several ordinary multivariate regression methods such as K-matrix, P-matrix, and Q-matrix least-squares regressions and factor based methods such as Principal Component Regression and Partial Least-Squares Regression were applied for the calibration, and the results were compared. The Partial Least-Squares method gave best results, especially in the case of four dyes. Conventional multivariate methods can not resolve severe overlapping of the spectra of the dyes in the visible region of light. 1:2 metal complex dyes were used in this research and the aging and the tendency to aggregate of the dyes were examined. The dyeing system used is made up of the primary colors yellow, red, and blue, plus a brown. A VIS-spectrophotometer was applied for measuring the spectra of the dye solutions and L*a*b* values of some leather processing chemicals. The L*a*b* values were used when calculating color differences DELTAE for determining whether there would exist change in color versus time. DELTAE or gray scale are usually used for assessing change in color when testing color fastness of leather. When the value of DELTAE is known, it is easy to quantify the change.