This study proposed using a portable microscope combined with a smartphone and application (PhotoMetrix® application) to evaluate the authenticity of Brazilian banknotes (R$50 and R$100) and national driver’s licenses (NDL) through image acquisition (Samsung S7) and chemometric treatment (principal component analysis (PCA)). Six regions of the banknote were analyzed: holographic band; lower and upper tactile regions containing the number referring to the value of the note; microprints above the effigy (obverse); and numbers and the surroundings of the animal formed by microprints (reverse). For NDLs, the regions were the following: the coat of arms of the republic; the state map with microprints; optical ink variation; distorted positive microletters with technical failure; negative guilloche; typographic numbering; micro letter wire; and region with line printing. For the chemometric study with Photometrix®, we selected a region of interest (ROI) of 32 × 32 and 64 × 64 pixels with autoscaled data using the channels red (R), green (G), blue (B), hue (H), saturation (S), value (V), lightness (L) and intensity (I). We obtained excellent results for differentiating banknotes and NDLs, both by visual and chemometric analyses (PCA). This study demonstrates the effectiveness of using a portable microscope and a smartphone as a portable forensic tool that is fast, robust, low-cost and reliable.

The study of the spectrum of light has increased its range of action in the field of chemistry, with the help of several advanced equipment and innovative techniques that have become a strong ally of analytical chemistry. However, the simplicity of obtaining results integrated with mobile devices appears as an interesting path to be taken in the field of chemical analysis. This work addresses the dissemination of an application called REDGIM for smartphones on the Android platform capable of working with multivariate image analysis using chemometric methods through the luminous intensities of photos and R (red), G (green) and B (blue) channels. In order to show the potential of REDGIM, we propose two applications using the partial least squares (PLS) regression method: 1) quantification of free chlorine in tap water; and 2) quantification of cannabinol, (CBN, a type of cannabinoid) in marijuana and hashish samples. The free chlorine concentration obtained for two investigated samples was 0.73 and 0.74 mg L-1 and 0.74 and 0.76 mg L-1 by the spectrophotometer and by the application (container: cuvette), respectively. For the quantification of CBN in marijuana and hashish samples, the mean concentration ranged from 6.137 to 8.823 mg mL-1. The results obtained by the application are compatible with results from traditional techniques, such as UV-Vis spectrophotometry, for example. Therefore, REDGIM was proved to be a simple and accessible technological tool for the scientific community, being viable for chemical tests of a multivariate nature.

A new method to identify the authenticity of Brazilian banknotes (R$) is proposed using digital image analysis by a smartphone application, Photometrix®, associated with chemometric tools. Authentic banknotes (n = 4) obtained in local bank and falsified (n = 12) by the author himself by means of three printers (laser-Deskjet®, wax-Color Qube® and inkjet-Deskjet®) were used for the development of the methodology. An experimental planning was performed to evaluate the authenticity of the banknotes determining: the best region (holographic band, tactile region in the lower left and right upper number, effigy microimpressions, lower number left, animal figure, watermark and puzzle); Region of Interest (ROI) (16x16; 32x32 and 64x64 pixels), focal length (8, 12, 15 and 20 cm) and variation of the smartphone (Motorola G5 Plus, Samsung S7 and LG K10). The best regions chosen were effigy microimpressions and round the animal. Promising results were obtained from ROI 16x16 pixels with focal length fixed at 10 cm. Thus, the application presents promising features for analyzing the authenticity of banknotes by digital images making it fast, non-destructive, portable, with low cost, and can be accessed by all society.