10 Hardware of Near-Infrared Spectroscopy
263
Fig. 10.29 The PDS method
(c) PDS Method
The piecewise direct standardization (PDS) method is similar to the Shenk method. In
this method, the wavelength and absorbance are corrected using multivariate analysis
[19] (Fig. 10.29).
Using the absorbance values of K samples from the master and slave instruments,
the A
K
λ i
of the master at wavelength λ i can be calculated based on the slave absorbance
values (C
K
λ i
) in the wavelength band λ i−X to λ i+X using the coefficient (β
λ i
n ). The
coefficient (β
λ i
n ) can be calculated from the MLR, PCA, or PLS.
The direct standardization (DS) method involves using all the wavelength data of
the slave instrument.
In the calculation of the above corrections, it is important to ensure the
repeatability of the measurements for this standardization.