Rapid Characterization of Tanshinone Extract Powder by Near Infrared Spectroscopy

Table 6

Comparison of different preprocessing methods of partial least squares model for content of cryptotanshinone/mg·g⁻¹.

Preprocessing method	LVs	Calibration set				Validation set
			RMSEC	RMSECV	BIAScal		RMSEP	RPD	BIASpre
Raw	10	0.9922	0.0026	0.0049	0.0019	0.9798	0.0027	4.4	0.0021
S-G smooth	10	0.9921	0.0026	0.0049	0.0019	0.9796	0.0027	4.4	0.0022
Normalization	11	0.9963	0.0018	0.0033	0.0013	0.9969	0.0013	8.9	0.0011
S-T	11	0.9955	0.0020	0.0041	0.0015	0.9922	0.0014	8.1	0.0011
MSC	14	0.9983	0.0012	0.0029	0.0010	0.9921	0.0015	7.9	0.0012
S-G 1st	6	0.9883	0.0032	0.0041	0.0023	0.9949	0.0020	5.9	0.0016
S-G 2nd	6	0.9934	0.0024	0.0043	0.0016	0.9910	0.0015	7.7	0.0014
Baseline	8	0.9845	0.0036	0.0055	0.0025	0.9882	0.0021	5.6	0.0017
SNV	11	0.9962	0.0018	0.0037	0.0015	0.9963	0.0015	8.1	0.0010
WDS	8	0.9799	0.0041	0.0059	0.0029	0.9814	0.0023	5.1	0.0020

Raw means using the original spectra without any pretreatment; LVs means numbers of latent factors of the PLS model. and represent correlation coefficients for calibration and validation sets, respectively. RMSEC, RMSECV, and RMSEP represent the root mean square error of calibration, cross validation, and prediction, respectively. BIAS_cal and BIAS_pre represent bias for calibration and validation, respectively. RPD means relative predictive deviation.
S-G smooth means Savitzky-Golay smoothing; S-T represents spectroscopic transformation; MSC means multiplicative scatter correction; S-G 1st is Savitzky-Golay smoothing plus first-order derivatives for short; S-G 2nd means Savitzky-Golay smoothing plus first-order derivatives; baseline means baseline correction; SNV represents standard normal variate transformation and WDS is wavelet denoise of spectra for short.