Fluorescence Spectroscopy Applied to Monitoring Biodiesel Degradation: Correlation with Acid Value and UV Absorption Analyses.

Maydla Dos Santos Vasconcelos,Anderson Rodrigues Lima Caires,Caroline Honaiser Lescanos,Rozanna Marques Muzzi,Magno Aparecido Gonçalves Trindade,Ivan Pires De Oliveira,Wilson Espíndola Passos

doi:10.1155/2018/4175843

Abstract

The techniques used to monitor the quality of the biodiesel are intensely discussed in the literature, partly because of the different oil sources and their intrinsic physicochemical characteristics. This study aimed to monitor the thermal degradation of the fatty acid methyl esters of Sesamum indicum L. and Raphanus sativus L. biodiesels (SILB and RSLB, resp.). The results showed that both biodiesels present a high content of unsaturated fatty acids, ∼84% (SILB) and ∼90% (RSLB). The SILB had a high content of polyunsaturated linoleic fatty acid (18 : 2), about 49%, and the oleic monounsaturated (18 : 1), ∼34%. On the other hand, RSLB presented a considerable content of linolenic fatty acid (18 : 3), ∼11%. The biodiesel samples were thermal degraded at 110°C for 48 hours, and acid value, UV absorption, and fluorescence spectroscopy analysis were carried out. The results revealed that both absorption and fluorescence presented a correlation with acid value as a function of degradation time by monitoring absorptions at 232 and 270 nm as well as the emission at 424 nm. Although the obtained correlation is not completely linear, a direct correlation was observed in both cases, revealing that both properties can be potentially used for monitoring the biodiesel degradation.

Highlights

E techniques used to monitor the quality of the biodiesel are intensely discussed in the literature, partly because of the different oil sources and their intrinsic physicochemical characteristics. is study aimed to monitor the thermal degradation of the fatty acid methyl esters of Sesamum indicum L. and Raphanus sativus L. biodiesels (SILB and RSLB, resp.). e results showed that both biodiesels present a high content of unsaturated fatty acids, ∼84% (SILB) and ∼90% (RSLB). e SILB had a high content of polyunsaturated linoleic fatty acid (18 : 2), about 49%, and the oleic monounsaturated (18 : 1), ∼34%
RSLB presented a considerable content of linolenic fatty acid (18 : 3), ∼11%. e biodiesel samples were thermal degraded at 110°C for 48 hours, and acid value, UV absorption, and fluorescence spectroscopy analysis were carried out. e results revealed that both absorption and fluorescence presented a correlation with acid value as a function of degradation time by monitoring absorptions at 232 and 270 nm as well as the emission at 424 nm
Raphanus sativus L. (RSL) and Sesamum indicum L. (SIL) seeds were commercially obtained from local companies. e seeds were dehydrated in laboratory oven under temperature of 60°C for 14 hours. en, the seeds were submitted to hydraulic press extraction obtaining a yield of extracted oil of 32% (w/w) and 45% (w/w) for RSL and SIL oils, respectively. e extracted oils were kept in a dark environment at −4°C until methyl esters synthesis

Summary

Research Article

Fluorescence Spectroscopy Applied to Monitoring Biodiesel Degradation: Correlation with Acid Value and UV Absorption Analyses. Is study aimed to monitor the thermal degradation of the fatty acid methyl esters of Sesamum indicum L. and Raphanus sativus L. biodiesels (SILB and RSLB, resp.). E desirable characteristics of the raw materials for biodiesel production include (i) adaptability to local growing conditions; (ii) regional availability; (iii) high oil content; Journal of Analytical Methods in Chemistry (iv) favorable fatty acid composition; (v) compatibility with existing agricultural practices; (vi) agricultural inputs; (vii) by-product markets; (viii) land compatibility; and (ix) rotational adaptability with other cultures [7]. The optical behavior is still not completely understood for biodiesel, especially for unconventional vegetable sources studied here (from Raphanus sativus L. and Sesamum indicum L. seeds) In this sense, the present study aimed to apply fluorescence spectroscopy for monitoring biodiesel degradation and determine its correlation with acid value and UV absorbance changes

Materials and Methods

Results and Discussion

Erucic Lignoceric Nervonic

Relative absorbance