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문제 정의
- Our main objective for this research was thus to find feasibility of using this mass spectrometry in quantitative identification of cashmere and yak fibers. The emphasis was made on two hardly-distinguishable fibers under microscopy, dark brown cashmere and dark brown yak.
제안 방법
- The test specimen was prepared by de-fibrating the fabric samples. Finally, five chemically treated samples were chosen to investigate effects of chemical treatment on quantitative analyses.
- Isotopes were generally used as a reference compound to enhance reliability and reproducibility of MALDI-TOF mass spectrometry in the previous studies [8]. Normalization of the intensity of yak specific ion peak by intensity of cashmere specific ion peak used in this study was able to increase reliability of the analysis and avoid the use of isotope. Examination of various combinations of yak specific ion peak against cashmere specific ion peaks demonstrated that a combination of m/z 1431 for yak and 1486 for cashmere provided the best results.
- Figure 7. Relationship between intensity of yak ion peak (m/z 1431) and yak content for mixture of yak and cashmere fibers at 5:95, 10:90, 15:85, 20:80, 30:70, 40:60, 45:55, 50:50, 55:45, 60:40, 70:30, 80:20, 90:10, 95:5 (w/w).
- Figure 8. Relationship between relative intensity of yak ion peak (m/z 1431) and yak content for mixture of yak and cashmere fibers at 5:95, 10:90, 15:85, 20:80, 30:70, 40:60, 45:55, 50:50, 55:45, 60:40, 70:30, 80:20, 90:10, 95:5 (w/w).
- The study firstly reaffirmed and modified qualitative analysis of cashmere and yak to investigate species-specific ion peaks by using MALDI-TOF mass spectrometry. A range of m/z was expanded to 1000−4000 Daltons.
- Two mixed samples were prepared for each yak-cashmere composition and four replications were carried out for each composition to improve reproducibility of analyses.
대상 데이터
- We also quantitatively evaluated chemically-treated commercial specimens to corroborate efficacy of this test. Five dyed, bleached, and/or depigmented commercial specimens were selected and examined. For a comparison purpose, both OM and SEM microscopic methods were also employed.
이론/모형
- All the specimens contained yak fibers from 6.1−34.0% as analyzed by MALDI-TOF method.
- MALDI-TOF mass spectroscope (Bruker Autoflex Speed LRF MALDI-TOF type, Bruker-Daltonic, Bremen, Germany) was used in this study with a target plate (MTP 384 target ground steel TF) and Smartbeam-II laser (355 nm, energy 100 µJ/pulse, maximum 500 µJ).
- The emphasis was made on two hardly-distinguishable fibers under microscopy, dark brown cashmere and dark brown yak. To confirm reliability of this quantitative analysis, commercial cashmereyak blend samples were also investigated by MALDI-TOF method. Furthermore, this test method was compared with conventional microscopic methods.
- Furthermore, this test method was compared with conventional microscopic methods. To select specie-specific ion peaks for quantitative analysis, qualitative identification of these fibers were carried out by MALDI-TOF mass spectrometry for specimens in CCMI (Cashmere and Camel Hair Manufacturers Institute) Fiber Box 2011 by MALDITOF mass spectrometry.
성능/효과
- Normalization of the intensity of yak specific ion peak by intensity of cashmere specific ion peak used in this study was able to increase reliability of the analysis and avoid the use of isotope. Examination of various combinations of yak specific ion peak against cashmere specific ion peaks demonstrated that a combination of m/z 1431 for yak and 1486 for cashmere provided the best results. Therefore, the equation below described a relative peak intensity of yak specific ion peak (m/z 1431) normalized by intensity of cashmere specific ion peak (m/z 1486) for each composition and the calibration curve is shown in Figure 8.
- Cashmere Specific Ion Peak: To find cashmere specific ion peaks, 32 mass spectra for both cashmere and yak fibers were carefully interpreted and compared. Results revealed that m/z 1486, 2036, 2634, and 3266 ion peaks were only presented in cashmere fibers, and these ion peaks were defined as cashmere specific ion peaks. Cashmere specific ion peaks observed in the previous study [11] were m/z 2036, 2634, and 3266.
- The results obtained by two analytical methods were quite similar with less than ±5% margin of error except specimen 8 (Dark indigo samples).
후속연구
- Therefore, MALDI-TOF mass spectroscopy can be quantitatively used in dyed, bleached, or depigmented single fiber specimens with a certain level of reliability and reproducibility over conventional microscopic methods requiring expert evaluation. For blended or mixture fabrics with highly dyed, bleached, or depigmented fibers, however, needed an additional study to deduce the final conclusion.
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