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Title: Transfer of nir calibration model for determining fiber content in flax; effects of transfer samples and standardization procedure

Author
item Sohn, Mi Ryeong
item Barton Ii, Franklin
item Himmelsbach, David

Submitted to: Applied Spectroscopy
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/29/2007
Publication Date: 4/1/2007
Citation: Sohn, M., Barton Ii, F.E., Himmelsbach, D.S. 2007. Transfer of nir calibration model for determining fiber content in flax; effects of transfer samples and standardization procedure. Applied Spectroscopy. 61(4): 414-418(5). 2007.

Interpretive Summary: Transfer of calibration models between instruments has been a long-standing issue in applied spectroscopy and remains as an important subject. Different spectral response problems are caused by wavelength differences or absorbance differences between instruments due to aging/changing parts and temperature. Even though instruments are identical, calibration transfer is always an issue because the instruments do not produce exactly the same response when measuring the same sample. The goals of this study were to transfer a near-infrared calibration model for determining fiber content in flax stem developed on one instrument to another instrument having different response characteristics and to obtain the best model through various standardization approaches. This paper describes how the calibration transfer was successfully accomplished by using a proper transfer sample set and by changing the standardization procedure. The research results will have interest for a broad audience working in the field of algorithm development for spectroscopic data and its transfer.

Technical Abstract: The transfer of a calibration model for determining fiber content in flax stem was accomplished between two near-infrared spectrometers, which are the same brand but require a standardization. In this paper, three factors including: transfer sample set, spectral type, and standardization method were investigated to obtain the best standardization result. Twelve standardization files were produced from two sets of the transfer sample (sealed reference standards and a subset of the prediction set), two types of the transfer sample spectra (raw and preprocessed spectra), and three standardization methods (direct standardization (DS), piecewise direct standardization (PDS) and double window piecewise direct standardization (DWPDS)). The efficacy of the model transfer was evaluated based on the root mean square error of prediction, calculated using the independent prediction samples. Results indicated that the standardization using the sealed reference standards was unacceptable but the standardization using the prediction subset was adequate. The use of the preprocessed spectra of the transfer samples led to the calibration transfer that was successful, especially for the PDS and the DWPDS correction. Finally, standardization using the prediction subset and their preprocessed spectra with DWPDS correction proved to be the best method for transferring the model.