Discrimination of counterpest fifty Ringgit Malaysia banknotes using attenuated total reflectance-fourier transform infrared spectroscopy and chemometric methods

Abstract

Counterfeiting of banknotes is one of the oldest criminal activities since 5th century AD and it still a constant concern to various countries including Malaysia because of its effects on the economy. With the continuous improvement and advanced printing technology nowadays, the task of identifying counterfeit banknote is getting more formidable. This study presents the Attenuated Total Reflectance-Fourier Transform Infrared (ATR-FTIR) spectroscopy in combination with chemometric tools as an analytical method to discriminate authentic and counterfeit RM50 banknotes. The counterfeit RM50 banknotes were obtained on loan from Commercial Crime Investigation Department (CCID), Royal Malaysia Police (RMP). The RM50 banknotes samples were first examined under video spectral comparator (VSC) followed by the characterization of the genuine and counterfeit RM50 banknotes in the IR fingerprint region (1800-650 cm-1) using ATR-FTIR. Fifteen areas of the RM50 banknotes samples were scanned for examining its functional groups in the IR fingerprint region and five areas of the RM50 banknotes samples were then selected into chemometric study. These parameters were computed using Solo 8.6 software to determine the organization of dataset and the main contributing factors for grouping using the unsupervised PCA. Supervised PLS-DA models were developed for predicting the unknown samples. PCA scores with more than 90% of variances was attained illustrating it as the main factors contributing for grouping. Although ATRFTIR spectra was adequate for differentiating the genuine and counterfeit RM50 banknotes samples, PCA was applied for better separation in view of its practical values in forensic investigations, resulting few distinct clusters differentiating the genuine and counterfeit RM50 banknotes samples and within the counterfeit RM50 banknotes samples. The reliability of the PLS-DA results were examined based on its RMSEC, RMSECV and RMSEP values, and were acceptable for discrimination of genuine and counterfeit RM50 banknotes samples. Hence, the method of ATR-FTIR spectral data coupled with PCA and PLS-DA can be adopted as a useful complementary tool in RMP investigation for discriminating the genuine and counterfeit RM50 banknotes samples.