Chromatographic and Spectrophotometric Determination of Some Direct TextileDyes Before & After their Degradation

In the present work, simple and sensitive HPLC method was developed for quantitative determination of four direct dyes (Direct Blue 2, Direct Red 23, Direct Green 1 and Direct Yellow 12). The maximum absorbance values for the above-mentioned dyes were found to be at 574 nm, 508 nm, 603 nm and 399 nm, with retention times of 2.9, 5.7, 6.1 and 6. 7 min, respectively. The mobile phase used was consisting of acetonitrile: water (60:40, v/v) containing 0.45 M Nــ cetyl ــN,N,N ــtrimethyl ammonium bromide (CTAB). RP C18 column was used with a flow rate of 0.5 ml/ min. Calibration graphs were found to be linear over the range 0.5-10 ppm for each of Direct Blue 2, Direct Red 23 and Direct Green 1 and 0.5-20 ppm for Direct Yellow 12. The relative standard deviation values were found to be 1.79%, 0.90%, 1.20% and 0.30% for the above-mentioned dyes, respectively. The effect of pH, flow rate of mobile phase and the concentration of CTAB on the determination of the four dyes have been investigated. The degradation kinetics of the four diazo dyes, Blue 2, Direct Red 23, Direct Green 1 and Direct Yellow 12 by iron metal in aqueous solution were studied. The results show that the rate of degradation is affected by the acidity, surface area of iron and temperature of the solution.The rates of degradation of the four dyes in aqueous solutions in presence of different metals (Co, Cu, Ni, Mn, Zn, Al and Fe), using UV light were studied. The obtained results showed that the rate of degradation was highest in the presence of aluminum metal and the rate of degradation was found to be higher when degradation was accompanied by exposure to UV light.