Rapid FTIR determination of water, phenolics and antioxidant activity of olive oil

A rapid Fourier transformed infrared (FTIR) attenuated total reflectance (ATR) spectroscopic method was applied to the determination of water content (WC), total phenol amount (TP) and antioxidant activity (ABTS.þ) of virgin olive oils (VOO) and olive oils. Calibration models were constructed using partial least squares regression. Oil samples with WC ranging from 289 to 1402 mg water/kg oil, with TP from 46 to 877 mg gallic acid/kg oil and with ABTS.þ from 0 to 5.7 mmol Trolox/kg oil were considered for chemometric analysis. Better results were obtained when selecting suitable spectral ranges; in particular, from 2260 to 1008 cm1 for WC, from 3610 to 816 cm1 for TP and from 3707 to 1105 cm1 for ABTS.þ. Satisfactory LOD values by the FTIR-chemometric methods were achieved: 9.4 (mg/kg oil) forWC; 12.5 (mg gallic acid/kg oil) for TP, and 0.76 (mmol Trolox/kg oil) for ABTS.þ. The evaluation of the applicability of these analytical approaches was tested by use of validation sample sets (n ¼ 16 forWC, n ¼ 11 for TP and n ¼ 14 for ABTS) with nearly quantitative recovery rates (99–114%). The FTIR–ATR method provided results that were comparable to conventional procedures.