Structure identification of reactive dyes by high performance liquid chromatography-photodiode array detection/mass spectrometry

Abstract

Based on years of experience on analyzing reactive dyes by high performance liquid chromatography-photodiode array detection/mass spectrometry (HPLC-DAD/MS), the essential applications for current structure identification of the commercial reactive dyes are summa- rized in three aspects. Commercial dyes always include several kinds of components. They are assistants for increasing solubility of synthetic dyes, multi-color synthetic dyes and their by-products derived from synthesis and storage. HPLC-DAD/MS technique can separate most of the components, and provide UV-Vis spectra and mass spectra individually. The separation and analysis can be achieved only through one injection without pre-purification of commercial dyes. Compared with traditional analytical methods, HPLC-DAD/MS technique reduces greatly not only the workload of analysis but also provides fully the actual compositions of the dyestuff. The reactive groups can react with ethanolamine or diethanolamine under moderate condition without structure destruction of dyes. The molecular masses before and after derivatization can be determined by MS, and then the type and number of reactive groups can be ascertained by so called "mass difference by derivative method". The chromophore of the dye can be identified by full spectrum scanning function of DAD. HPLC-DAD/MS analytical technique is very special and useful for the structure analysis of multi-component mixed commercial dyes. As examples, the identifications of three multi-component mixed structures of commercial dyes (Reactive Gray, Reactive Supra Black and Reactive Marine Blue) were given.