Maintaining the predictive abilities of multivariate calibration models by spectral space transformation

Wen Du, Zeng-Ping Chen, Li-Jing Zhong, Shu-Xia Wang, Ru-Qin Yu, Alison Nordon, David Littlejohn, Megan Holden

Research output: Contribution to journalArticlepeer-review

93 Citations (Scopus)


In quantitative on-line/in-line monitoring of chemical and bio-chemical processes using spectroscopic instruments, multivariate calibration models are indispensable for the extraction of chemical information from complex spectroscopic measurements. The development of reliable multivariate calibration models is generally time-consuming and costly. Therefore, once a reliable multivariate calibration model is established, it is expected to be used for an extended period. However, any change in the instrumental response or variations in the measurement conditions can renders multivariate calibration model invalid. In this contribution, a new method, spectral space transformation (SST), has been developed to maintain the predictive abilities of multivariate calibration models when the spectrometer or measurement conditions are altered. SST tries to eliminate the spectral differences induced by the changes in instruments or measurement conditions through the transformation between two spectral spaces spanned by the corresponding spectra of a subset of standardization samples measured on two instruments or under two sets of experimental conditions. The performance of the method has been tested on two data sets comprising NIR and MIR spectra. The experimental results show that SST can achieve satisfactory analyte predictions from spectroscopic measurements subject to spectrometer/probe alteration, when only a few standardization samples are used. Compared with the existing popular methods designed for the same purpose. i.e. global PLS, univariate slope and bias correction (SBC) and piecewise direct standardization (PDS). SST has the advantages of implementation simplicity, wider applicability and better performance in terms of predictive accuracy.

Original languageEnglish
Pages (from-to)64-70
Number of pages7
JournalAnalytica Chimica Acta
Issue number1
Early online date12 Feb 2011
Publication statusPublished - 25 Mar 2011


  • calibration model maintenance
  • spectral space transformation
  • spectral standardization
  • spectroscopic instruments
  • process analytical technology
  • infrared spectrometric instruments
  • standardization procedure
  • genetic regression
  • raman-spectroscopy
  • neural network
  • improvement
  • algorithm
  • transferability
  • linearity


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