Simultaneous Determination of Caffeine and Taurine in Energy Drinks by FT-MIR Spectroscopy Coupled with Multivariate Analysis

Table 2

Calibration and validation data of the models based on FT-MIR spectroscopy.

Calibration (n = 40)					Validation (n = 10)
Algorithm	Parameter	Factors^a	Rc^2b	SEC^c	Rv^2d	SEP^e	MD^f	RR^g	RE^h	RPD^i	%RD^j
PCR	Taurine	8	0.7067	6.50	—	8.34
	Caffeine	10	0.6453	198.21	—	166.90
PLS1	Taurine	5	0.9999	0.15	0.9997	0.16	0.11–0.54	0.64–1.78	0.74–0.95	14.37	1.68–7.29
	Caffeine	7	0.9999	0.26	0.9999	0.32	0.13–0.45	0.87–1.91	0.63–0.81	8.67	5.38–8.34
PLS2	Taurine	20	0.9950	1.23	—	3.11
	Caffeine	20	0.9921	40.36	—	24.14

^aFactors or latent variables. ^bRc²: determination coefficient of calibration, must be as close as possible to 1. ^cSEC: standard error of calibration, must be as low as possible. ^dRv²: determination coefficient of validation, must be as close as possible to 1. ^eSEP: standard error of prediction, must be as low as possible. ^fMD: Mahalanobis distance, must be lower than 1; ^gRR: residual ratio, must be lower than 3. ^hRE: residual error, must be as low as possible. ⁱRPD: residual predicted deviation (SD/SEP), must be as high as possible. ^j%RD: relative difference percentage, must be lower than 10%.