Analysis of commercial Acid Black 194 and related dyes by micellar electrokinetic chromatography

The commercial dye C.I. Acid Black 194 was analyzed by reversed-phase HPLC, Capillary Zone Electrophoresis and Micellar ElectroKinetic Chromatography under different operative conditions, with the scope to detect the impurity distribution typical of any production processes and synthetic batch. The three chrome(III) complexes deriving from the industrial synthesis of C.I. Acid Black 194, and one of the main impurities were isolated by silica flash chromatography and identified by mass spectrometry and NMR. More than twelve compounds present in the commercial mixture, but undetectable by the analytical protocols known in literature, were fully separated by the MECK mode capillary electrophoresis with low % Relative Standard Deviation of the main electrophoretic parameters. Two of them were identified by isolation from the commercial mixture. As additional examples two other commercial metal-based dyes, C.I. Acid Brown 432 and C.I. Acid Brown 434, were analyzed by the same protocol with very good results.