Near infrared reflectance spectroscopy as a tool for the determination of dichloromethane extractable matter and moisture content in combed wool slivers

In the wool textile field the quantitative determination of solvent extractable matter and moisture content is a crucial analysis for the evaluation of combed sliver quality. The test carried out includes the acquisition of a series of data about dichloromethane soluble matter (according to the International Wool Textile Organisation-IWTO 1001 specification), and moisture content in combed wool slivers and the search for a correlation between these data and the near infrared spectra of samples. Combed wool slivers tested were of different origins and variable mean diameters and were obtained from different combing mills in the industrial district of Biella, the principal wool textile region of Italy. The spectrophotometer used was a FT-NIR system (Perkin-Elmer Spectrum IdentiCheck). Spectra were collected in the region from 3700 to 10,000 cm(-1) in reflection mode. The extraction of greasy matter from wool tops was carried out with a continuous extraction technique on a 10 g wool sample with a total extraction time of about 3 hours in a soxhlet apparatus. The results express the weight (obtained by the mean of two determinations) of the dichloromethane soluble extract as a percentage of the dry weight of the de-greased sample. For the determination of dichloromethane extractable matter, 103 samples were used for calibration. Some wool samples were deliberately under-scoured and others were re-scoured in a combing mill in order to obtain a wide range of data, ranging from 1.15 % to 0.21 %. Spectra were analysed using Quant+ (Perkin-Elmer Software). The best results were obtained with the PLS1 (Partial Least Square) algorithm when considering the spectral region 9000-3800 cm(-1) [Standard Error of Prediction (SEP) = 0.1042, mean value (M) = 0.6963%, Coefficient of Determination (R-2) = 0.85]. A cross-validation was used. The determination of moisture content in combed wool sliver was performed by drying wool (80 g for a single determination) in an oven to constant weight using forced air at 105 +/- 2degreesC. 85 samples were used for the calibration. Deliberate variations in regain were induced by exposing the wool to a dry or moist atmosphere. In this way moisture contents ranging from 9% to 15% were obtained. NIR spectra were analysed using Quant+ Software. A cross-validation was used. The best results were obtained with the Principal Component Regression algorithm when considering the spectral region 9000-3800 cm(-1). A SEP of 0.4954 (M = 11.76 %)and a R-2 of 0.90 were found. A limited number of determinations of grease and moisture content were carried out using the models obtained and compared with values determined manually.