Determination of Free Fatty Acid by FT-NIR Spectroscopy in Esterification Reaction for Biodiesel Production

Table 1

Cross-validation and external validation results for the prediction of FFA content (%) using different pretreatment methods.

Parameter	Baseline correction^a	^a+SG smoothing^b	^b+Derivative^c
PLS factors	17	17	17
𝑅^2 calibration	0.819	0.8124	0.9487
𝑅^2 validation	0.966	0.9698	0.9407
RMSEC (%)	2.022	1.968	1.35
RMSEV (%)	3.706	2.685	1.68

 ^aObtained using as reference the spectra without pretreatment.
^bSavitzky-Golay smoothing.
^cFirst derivative obtained by the Savitzky-Golay method.