Simultaneous Quantification of 14 Compounds in Achillea millefolium by GC-MS Analysis and Near-Infrared Spectroscopy Combined with Multivariate Techniques

Table 2

Comparison of the optimized parameters for developing the NIR single-compound regression models (SCM) and the multiple compound regression model (MCM).

Sample preparation^1	Model	Compound	n^2	Wavenumber (cm^−1)	Data pretreatment	Method	Factors
Sair	SCM	C1	52/26	4008–9996	MSC	PLS	5
		C2	52/26	4008–9996	MSC	PLS	6
		C3	52/26	4008–9996	MSC	PLS	7
		C4	52/26	4596–9996	MSC	PLS	6
		C5	52/26	4008–9996	MSC	PLS	7
		C6	52/26	4008–9996	MSC	PLS	11
		C7	52/26	4008–9996	Smoothing (Savitzky–Golay, 9 points)	PLS	8
		C8	52/26	4596–9996	MSC	PLS	6
		C9	52/26	4440–9000	First derivative (Savitzky–Golay, 9 points); normalization to unit length	PLS	11
		C10	52/26	4440–9000	First derivative (Savitzky–Golay, 9 points); normalization to unit length	PLS	5
		C11	52/26	4440–9000	First derivative (BCAP); normalization by closure	PLS	11
		C12	52/26	4008–9996	MSC	PLS	6
		C13	52/26	4008–9996	MSC	PLS	6
		C14	52/26	4596–9996	Log (1/R); normalization by closure; second derivative (Savitzky–Golay, 9 points)	PLS	12
Sair	MCM	C1–14	52/26	4008–9996	MSC	PLS	8
Soven		C1–14	24/12	4596–9996	First derivative (BCAP); normalization by closure	PLS	5
Sair-and-oven		C1–14	76/38	4008–9996	Normalization by closure	PCR	12

¹S_air = air-dried A. millefolium; S_oven = oven-dried A. millefolium; S_air-and-oven = mixture of air-dried and oven-dried A. millefolium, ²sample number in the calibration set/sample numbers in the validation set.