| The naturally color cotton with natural color as “green†and environmental-friendly fiber material is not essential to dye, reducing environmental pollution caused by dye, and it is favored by textile factory with a series of antibacterial property, antioxidative property and fire-resistance. However, the fiber’s poor strength and quality, mono-color, and unstable pigment in naturally color cotton restrict the development and application of naturally color cotton. The research of naturally brown cotton is hopeful to obtain the structure of pigment components to know about the essential reason of unstable pigment to take measure to avoid even resolve the problem of unstable pigment, which has an influence on popularization and application of naturally brown cotton in a certain extent. Firstly, in order to study the multicomponent character of pigments in naturally brown cotton, chromatographic column filled with C18 is used to separate pigment components. Then, the chromogenic reaction happens between butanol-HCl with pigments of naturally brown cotton to identify and quantify condensed tannin percentage in naturally brown cotton by UV detection. At last, The HPLC chromatograms of pigments of naturally light, medium, and dark brown cotton are compared with each other.The HPLC chromatograms of extracted-pigments of naturally brown cotton eluted by different concentration of methanol solution through C18 column indicate that it is excellently separated before 5min retention time and pigment at 1.4min retention time has a high content, however, it appears “bread shaped†peak which is not easily separated between 7~17min retention time. The extracted-pigments in naturally brown cotton are divided by self-filled C18 chromatographic column eluting with different concentration methanol solutions from low concentration to high concentration, then pigment components are detected by HPLC and UV. It indicates that pigment at 1.4min retention time is completely eluted by 5% methanol-water solution, then it can collect the pigment at 1.4min retention time by 5% methanol-water solution. The “bread shaped†peak of retention time between 7~17min in HPLC chromatogram is preliminary separated by different concentration methanol solutions with different polarities to many thin peaks(not sharp peaks), so it is mixture still and remains to study further. It shows the “bread shaped†peak materials consist of different polarity substances indeed, while the condition of HPLC in this research can’t divide the “bread shaped†peak perfectly. The UV spectrograms of pigment components eluted by different concentration methanol solutions are very similar with each other, which indicates that pigments have similar structure.The content of condensed tannin in naturally brown cotton is quantified by the butanol-HCl method, and the quantitive analysis method of the content of condensed tannin is confirmed. Pigments of the naturally brown cotton after mixing with the butanol-HCl solution are heated in water-bath at 95 ℃ for 1h, then, after color completely changes, it is detected by UV Spectrophotometer to measure the content of condensed tannin in naturally brown cotton at wavelength 500 nm through colorimetric method. The condensed tannin percentage in naturally brown cotton is calculated to be 1.57% under the condition of this article’s experiment. The pigments before 5min retention time in the HPLC chromatogram haven’t condensed tannin. However, the data suggests that the pigments between 7~17min retention time in the HPLC chromatogram all have condensed tannin and the content of condensed tannin is a small fraction of “bread shaped†peak substances. Therefore, the other pigment components remain to be further research.The HPLC chromatograms of pigments in the naturally light, medium and dark brown cotton extracted by 30% ethanol solutions show the peak’s shapes of chromatograms are very similar, and all have pigment’s components at 1.4min, 1.7min and 1.8min retention time, while the percentage of this three pigment’s components is highest in extracted-pigments of the naturally light brown cotton. Pigments at 2.3min and 2.8min retention time exist in extracted-pigments of the naturally medium and dark brown cotton, however, pigments at 2.5min, 2.9min and 3.3min retention time only exist in the naturally light brown cotton. It indicates that pigments before 5min retention time have the same and different components in the three kinds of naturally brown cotton, and the “bread shaped†peak shapes between 7~17min retention time in the HPLC chromatogram is similar in the three kinds of naturally brown cotton.The extracted-pigment in the naturally brown cotton has condensed tannin, while the content of condensed tannin isn’t high, and it also has a kind of substances with similar polarity and structure, and difficult separation. The HPLC chromatograms of pigments in the naturally brown cotton with different degrees of color are similar to speculate they have the similar structure and pigment’s components, which proves that pigment’s components in naturally brown cotton are complex further. |
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