Study of analytical methods for quantifying unfixed form of bifunctional reactive dyes used in dyeing cellulosic fibers (cotton)

Abstract

The objective of the present study was to examine the reliability and compatibility of three methods for quantifying the unfixed form of heterobifunctional reactive dye type monochlorotriazine/β-sulfatoethylsulfone used in dyeing cellulosic fibers (cotton). The first method is based on spectrophotometric analysis by measuring the absorbance of residual dyebath (after dyeing process) and residual soaping bath (after washing-off phase), the second one is based on colorimetric analysis by measuring the reflectance of dyed fabric, and the third on high-performance liquid chromatography (HPLC) technique. The purpose of the latter is to identify and quantify the hydrolyzed and inactive forms of dye in residual soaping bath. The calculated unfixed dye rates unequivocally prove the reliability and compatibility of these methods. According to the availability of the required laboratory instruments, we can select the most suitable method in every case, though the tests proved that the HPLC technique is most efficient.