Detection oxidative degradation in lubricating oil under storage conditions using digital images and chemometrics

Chemometrics‐assisted color histogram‐based analytical systems

“…Glass, quartz or prismatic PTFE cuvettes 17,[29][30][31] and flow cells 32,33 have been used similarly to spectrophotometry involving specific colorimetric reactions, replacing exclusively the detector. Other common holders have included glass, plastic and lab-made polytetrafluorethylene (PTFE) Petri plates 25,27,28,[34][35][36][37][38][39][40][41][42][43][44][45][46] have been the most employed holder type to dispose the samples directly without pretreatment. PTFE chambers of automated Flow-Batch Analyzers 26,47 have been also used to prepare samples and calibration solutions in flow into the mixing chamber.…”

“…Ribeiro et al 27 identified degradations in commercial lubricating oils, simulating storage conditions by heating in an oven at 60 C and radiation by UV exposition at different times (3,6, and 9 h). Accuracy, sensibility, and specificity rates of 100% were obtained for distinguishing nonoxidized samples from samples that have suffered an oxidation process using Grayscale+RGB + HSI histogram and PLS-DA.…”

“…In the examples that employ digital camera, 25 webcam 26 and scanner, 28 histogram extraction, and data analysis are performed in the offline mode in a computer. On the other hand, the example that uses the smartphone 27 can be considered a truly portable system that performs data acquisition, processing, and analysis simultaneously using the PhotoMetrix® app. In all cases, the principle of simplicity, versatility, and low cost of CACHAS are corroborated.As can be seen, a basic analytical system that employs color histograms as input data for construct multivariate models usually consists of four essential parts: A holder to conditionate the calibration objects and samples.…”

“…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.…”

PhotoMetrix and colorimetric image analysis using smartphones

“…By evaluating the works that used smartphones for image acquisition and performed the external processing of the acquired data (Figure 1), we can see that these devices are explored in several areas, such as the detection of diseases and markers of diseases causing in the medical field, immunoassay, 18–27 quality control of the environment, 28–39 forensic analysis, 40–42 control and quality of beverages and food, 15,43–64 quality evaluation of pharmaceutical products, 54,65,66 fuel quality control, 67,68 pigments, 69 chemical education, kinetic studies, and chemical receptors 70–77 …”