Fast Determination of Biodiesel Content in Commercial Diesel/ Biodiesel Blends by Using Digital Images and Multivariate Calibration

Abstract

A new simple, rapid and inexpensive analytical method was developed to determine the biodiesel percentage in biodiesel/ diesel blends through simple digital images of samples obtained by scanning with a commercial scanner. Soybean biodiesel and petroleum diesel samples were acquired from refineries currently in operation. There were prepared several mixtures within the range 1.5 to 12.0% of biodiesel in diesel oil, using the same procedure as is done in industry. The analytical signals were images recorded with a scanner. This data was decomposed with different color systems: RGB, HSV, HLS, CMYK and Grayscale. Chemometrics models based on color signals obtained from different mixtures of biodiesel/diesel were built. The quantification by using partial least squares (PLS) resulted in a RMSEP value for biodiesel of 0.9% (w/w); this load approximately 10-times smaller than the corresponding calibration range, with a correlation of 0.96 between predicted and reference values.

Chemometrics‐assisted color histogram‐based analytical systems

“…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.…”

“…Similar to what happens in applications involving classification, the main publications that use multivariate calibration in CACHAS has been directed mostly to food analysis. 15,30,31,[43][44][45]55,56,58 In addition, applications in agricultural, 46,49 microbiological 53 biological, 54 drug, 18 biofuel, 57 and mineral insulating oil 59 analyses have also been carried out. Here, although most of the studies do not also employ sample pretreatment, solvents, or reagents, the calibration models are dependent on the values obtained by reference methods or similar accurate measurements of the target property/analyte.…”

“…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. Other specific holders have been also designed in the laboratory for dedicated applications, such as panel for paint, 21 lab-made PTFE supports, 48,49 white A4 paper, 50 polyethylene bottle, 51 paper tray, 52 lab-made rubber ring, 15 immobilized calcium-alginate capsule, 53 ELISA (enzyme-linked immunosorbent assay) microplate, [54][55][56] thin layer chromatographic (TLC) plate, 18 glass vial, 57 lab-made PTFE cell, 58 test tube, 59 stage plate, 60 and kraft tapes. 61 2 An illumination source emitting a broad range of visible wavelengths (white light) has been employed to illuminate uniformly the holder.…”

“…The use of white light enables the differentiation between different tones, hues, and shades when histograms are constructed from a digital image. 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.…”