The Application of Raman Spectroscopic Ratiometric Analysis for Distinguishing between Wool and Mohair

Abstract

Wool and mohair fiber bundles were analyzed using a Fourier transform (FT) Raman system, equipped with a Nd:YAG excitation laser (1064 nm), with the aim of determining whether such a system can be used to distinguish between the two fiber types in practice. Wool and mohair fibers were found to have virtually identical Raman spectra, except for the relative peak heights of certain chemical bands. Nevertheless, the individual values of the wool and mohair peak height ratios B (I1655/I1450), C (I1004/I1450), E (I936/I1450), F (I644/I1450) and G (I622/I1450) varied and overlapped considerably although the mean values of two of the most promising ratios; namely A (I2932/I1450) and D (I508/I1450) differed statistically significantly (p < .05) for wool and mohair, their individual values overlapped considerably, ranging from 2.71 to 3.68 for A and 0.18 to 0.32 for D, respectively, for wool and from 2.35 to 3.08 and 0.17 to 0.22, respectively, for mohair. This meant that the application of these ratios, to distinguish between wool and mohair, will be extremely difficult if not impossible. Nevertheless, tentative threshold values were identified, using the frequency distributions of the individual values, for both ratios A and D, which can be used to determine whether or not a sample is pure mohair. It is necessary, however, to analyze a much larger number of wool and mohair samples from various countries to validate the accuracy (reliability) of these threshold values. From the results of this study, it can be concluded that the application of Raman spectroscopic ratiometric analysis could have a potential application in detecting counterfeiting in pure mohair products.

Keywords

• ratiometric analysis
• animal fibers
• fourier transform raman spectroscopy
• wool
• mohair