Comparison of extraction methods for the analysis of Indigofera tinctoria and Carthamus tinctorius in textiles by high performance liquid chromatography

The extractions of indigo (Indigofera tinctoria L.) and safflower (Carthamus tinctorius L) red and yellow from wool fibres are investigated using high performance liquid chromatography with photo-diode-array detection (HPLCPDA) which is frequently coupled to Mass Spectrometry (HPLC-PDA-MS) for identification purposes. The efficiencies of dimethyl sulfoxide (DMSO) and dimethyl formamide (DMF) to extract indigo and safflower from wool, are compared for a wide range of temperature (from 40 to 120 degrees C) and treatment time (from 1 to 30 min). Extraction procedures are investigated by measuring integrated HPLC peak areas of selected dyestuff components, evaluating simultaneously the effects of solvent (DMSO and DMF), treatment temperature (T) and time (t). Thus, cross-influence of the different extraction parameters (solvent, T and t) is taken into account. Indigotin, isatin and indirubin are monitored to evaluate the extraction of indigo. Carthamin, a decomposition product of carthamin, apigenin, safflomin A, 6-hydroxykaempferol-3-O-beta-D-glucoside, anhydrosafflor yellow Ct1 and Ct4 are monitored to investigate the extractions of safflower red and yellow. Overall, it is reported that DMSO gives better extraction yields than DMF. The best conditions for the extraction of the marker compounds of the three dyes are summarized as follows. For indigotin, treatments of the wool with DMSO at 80 degrees C for t >5 mm or at 120 degrees C mm for t = 1 mm give the best yield. Longer treatment (t >1 mm) at 120 degrees C results to decomposition of indigotin. For carthamin, treatments of the wool with DMSO at 80 degrees C for t >5 mm or at 120 degrees C mm for short t (<5 min) give the best yield, considering that longer (>5 min) treatment at 120 degrees C results to decomposition of the marker compound. Finally, for safflomin A treatments of the wool with DMSO at 100 degrees C for t > 10 min or at 120 degrees C mm for t = 5 mm give the best result. (C) 2014 Elsevier B.V. All rights reserved.