Quantitative Determination of Dyes in Textile Fibers
1975
Kissa, Erik
The quantitative determination of nonionic dyes in polyester substrates by extraction with organic solvents has been studied. Highly accurate and precise results are obtained by extraction of the fabric or yarn (0.1 to 0.3 g sample) with dimethylformamide (DMF) containing a free radical inhibitor (5 to 20 g/l. 2,6-di-t-butyl-4-methylphenol) and a non volatile acid (p-toluenesulfonic acid) to lower the apparent pH of the solvent to 4.0. One extraction with this solvent at 140°C removes usually over 90% of the dye in 2 to 3 minutes. Most dyes are removed completely from the fiber by three extractions (3 min each). The method is also applicable to the quantitative determination of disperse dyes in polyamide, acrylic, and acetate fibers and DMF soluble nonionic dyes in cellulosic fiber. It is shown that extraction with hot DMF can give erroneous results unless a free-radical inhibitor is added and the acidity of the extraction solvent controlled to stabilize the solvent and the dye. Stabilized DMF or dimethylacetamide (DMAC) are more effective extraction solvents than chlorobenzene, o-dichlorobenzene, dimethyl o-phthalate, methyl ethers of polyethylene glycols, acetic acid, or chloroform.
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