Extraction of Cotton Impurities: Supercritical Co2 vs. Soxhlet/TCE

Determination of residual natural waxes and processing lubricants on yarns and fabrics has traditionally been accomplished by Soxhlet extraction with an organic solvent. A variety of concerns about these solvents has driven a search for alternative methods. Hydrocarbon solvents; e.g., petroleum ether, are flammable and the manufacture of chlorofluorocarbon solvents was phased out in 1996 as a result of their effect on the ozone layer. Purchase and disposal of chlorinated solvents such as 1 ,I ,1-trichloroethane (TCE) are costly. One possible solution to this problem is to use a nontoxic supercritical fluid, carbon dioxide, as a medium for extracting materials from textile substrates. This paper describes development of a supercritical fluid extraction (SFE) method for the quantitative determination of natural cotton wax, paraffin winding wax, and knitting oil from cotton fibers, yarns, and fabrics. Analysis of the extracts by various analytical methods, including differential scanning calorimetry (DSC), Fourier transform infrared (FTIR) spectroscopy, gas chromatography (GC), and gas chromatographylmass spectrometry (GC/MS) techniques are also presented.