Principal Component Analysis of Commercial Tannin Extracts Using Digital Images on Mobile Devices

Abstract

Tannins from trees are an abundant renewable resource. The use of tannins is safe for the environment and human health, making it possible to develop environmentally friendly products, such as adhesives, flocculant agents for water treatment, flame retardant foams and anticorrosives. In this study, a methodology was developed for the identification of six commercial tannin extracts (chestnut, valonea, tara, myrobalan, quebracho and black wattle) using digital images on mobile devices. The identification of the extracts was based on principal component analysis using the PhotoMetrix ® mobile application. In the evaluation of the principal components, it was possible to define the separation between the six classes of extracts by color evaluation, according to the extract origin. In the analysis of PC1 × PC2, black wattle was very close to quebracho and chestnut was close to valonea; these extracts are chemically similar. The methodology developed for the analysis of tannin extracts obeys the principles of green chemistry requiring no reagents, and is fast, non-destructive and inexpensive.

Chemometrics‐assisted color histogram‐based analytical systems

“…Common sources include fluorescent lamps (either external or internal to a scanner 15,21,25,28,32,[34][35][36][37][38][39][42][43][44]46,48,49,[54][55][56][57] ) and white-light LED (light-emitting diode) lamps 26,27,30,33,40,41,45,47,58,59 or LED strips, 17,31,50 and they must be suitably disposed in the system in order to avoid shadows and illumination gradients under the ROI. Ultraviolet (UV) lamps, 18,51 near infrared (NIR) LEDs, 29 internal flash lamp, 52,61 white-light-transilluminator, 53 and luminoscope 60 have been also used. An important detail is that most applications employ a closed box to avoid interferences from the external luminosity and, consequently, future manipulations/corrections of the captured image.…”

“…3 An image capturing device to register the images of the chemical system under consideration. Simple commercial devices include digital cameras, 15,25,30,41,45,52,53,59,60 scanners, 21,28,34,35,39,43,46,[54][55][56][57]61 webcams, 26,29,32,33,[36][37][38]40,42,44,[47][48][49] and smartphones, 17,18,27,31,50,51,58 and the choice of one of them shall be according to its availability in each laboratory or specific need for a given application. However, it is important to note that the portability of systems through the use of smartphones has become a remarkable trend in the literature, mainly in applications involving univariate calibration for colorimetric analysis.…”

“…The development of green analytical methods aiming to supply authentic and high-quality agro-products has been emphasized by researchers as support to establish links to the consumers, farmers, traders, and regulatory agencies. In the case of CACHAS, this has been achieved by discriminating cultivars 48 and identifying the source of the raw materials 37,51 and the presence of impurities. 52 As food products have by nature a land-based, they can be addressed as a particular case of agricultural products that are influenced by geographically specific factors, that is, it is important to identify its geographical origin, which has been already discussed before.…”

PhotoMetrix and colorimetric image analysis using smartphones

“…Through the researches that used PhotoMetrix ® early presented, it is possible to visualize the versatility of this application, because it was used in different analysis, presenting significant results. It is possible to carry out direct analysis, 126,136 that is, without performing sample preparation, analysis of solid 120 and liquid samples, [131][132][133]135 with the use of chambers to store the samples, 121,124,125,129,134 or without lighting control accessories, 127 in addition to allowing the sample to be conditioned in different ways to capture images such as paper 122,123 and SDS-PAGE 128,130 for example. Figure 12 shows four different ways of acquiring images related to the previously presented articles that used Photo-Metrix app in their analysis, where in some works, chambers were made to capture images, and in others, the image acquisition was performed without light control.…”

Chromium speciation in leather samples: an experiment using digital images, mobile phone and environmental concepts

“…In 2016, a new free app called PhotoMetrix for image analysis was proposed by Grasel and coauthors 8 . The authors used PhotoMetrix for the identification of tannins according the source type (chestnut, valonea, quebracho, black wattle, tara and myrobalan).…”