Rapid authentication of turmeric powder adulterated with Curcuma zedoaria and Curcuma xanthorrhiza using FTIR-ATR spectroscopy and chemometrics

Abstract

Objective: The objective of this study is to develop a rapid, simple, non-destructive and inexpensive analytical method using Fourier Transform Infrared (FTIR) spectroscopy with Attenuated Total Reflection (ATR) as a sampling technique, combined with chemometrics for authentication of turmeric powder adulterated with Curcuma zedoaria and Curcuma xanthorrhiza. Methods: Turmeric powder is placed above the diamond crystal in ATR compartment. Spectra are scanned in the absorbance mode from 4000 to 600 cm-1. The obtained spectra is further analyzed by Principal Component Analysis (PCA), Partial Least Square Discriminant Analysis (PLS-DA), and Partial Least Square Regression (PLS-R). Results: PCA score plot shows that Curcuma longa, Curcuma zedoaria, and Curcuma xanthorrhiza can be discriminated well. PLS-DA can be used to build the model for classification between pure turmeric powder and adulterated powder with the value of Q2, R2X, and R2Y of 0.9558, 0.9813, and 0.9746, respectively. The good calibration model for quantification of each adulterant is obtained by PLS-R with R2 value more than 0.99 and lower RMSEC value. The models have been validated by internal and external validations, which resulting in the high R2 value and low RMSEP value which indicates that both models are accurate and precise. Conclusion: The combination of FTIR-ATR spectroscopy and chemometrics can be used to authenticate turmeric powder adulterated with Curcuma zedoaria and Curcuma xanthorrhiza.