DISCRIMINATION OF REACTIVE DYES ON COTTON FABRIC BY RAMAN-SPECTROSCOPY AND CHEMOMETRICS

FT-Raman spectra were obtained from undyed poplin cotton fabric and fr om the same fabric differently dyed with a bi-functional reactive dye, Cibacron C (molecular structure unknown); the four series of the dyed samples each contained the dye in a different form--unfixed, ammonia- treated/unfixed, fixed, and ammonia-treated/fixed. The spectra were do minated by the dye, but the different states of the dye were not obvio usly differentiated. Application of principal component analysis showe d that the spectral groups of the four different dye states can be dis criminated from each other and from that of the undyed cotton. Further , for each series of the dyed fabrics, which contain samples with diff erent amounts of dye, the individual dye concentration subgroups are d istinguished. Exploratory quantitative studies suggested that FT-Raman spectroscopy may be a suitable quantitative method for the prediction of % concentration of the unfixed dye on cotton fabrics. A comparison of the FT-Raman results with those from a parallel FT-IR study report ed elsewhere indicated that similar qualitative conclusions may be rea ched with both techniques. However, the FT-Raman approach does provide additional information from the dominating dye spectrum. A comparison of prediction of % concentration of the unfixed dye on the fabric ind icated that better partial least-squares (PLS) calibration models may be obtained from the FT-Raman data, but the validation results from a small set of samples suggested only a marginal advantage with the use of the Raman approach.