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No abstract

Steroids are called the "fingerprint" of oils, fats, and their derivatives. Different classes of steroids may be present in these matrices. Most of the methods developed to analyze these constituents involve the determination of free steroid content, although their conjugated forms are extremely important in determining the total composition. Thus, this article demonstrates that the coupling of sequential mass spectrometry and high-performance liquid chromatography obtained high sensitivity and high specificity of mass resolution to identify and quantify the main classes of steroids. Four methods were developed to quantify steroids free, esterified, glucosides, and acylated glucosides by internal standardization using betulin. The main validation parameters were tested and demonstrated good correlation results for the methods. The content of free steroids was the majority in all samples, whereas the content of glucoside steroids was the least abundant. The contents of free steroids quantified in the degummed soybean oil were significantly reduced in relation to the refined oil. A small amount of esterified steroids was superior in refined soybean oil than in degummed oil. Comparing the steroid content between degummed oil and biodiesel, we found that the concentration of free and esterified steroids decreases in the conversion to biodiesel, whereas the concentration of glucoside steroids increases slightly.

When the biodiesel enters the crankcase, its degradation can lead to the formation of organic acids and polymerisation, to the point of clogging the system and the internal combustion engines. Therefore, this article proposed the study of lubricant oils in order to trace its biodiesel contamination. The results showed that in relation to the viscosity at 40 C there was reduction above the limit allowed for some samples. The viscosity index results showed considerable changes. Using infrared spectroscopy was noted that the contamination by fatty acid esters does not follow a pattern related to time of use in the motor. However, as the lubricant oil samples were used, they probably contain degradation products that altered the levels of oxygenated compounds. For this reason, the mass spectrometry coupled to gas chromatography quantified the predominant oil and fat steroids contents and confirmed the contamination by biodiesel.

How these techniques coupled, high-performance liquid chromatography and mass spectrometry (LC-MS), revolutionized the field of chemical analysis. For a long time, the field of instrumental chemical analysis was limited, as we could not reliably quantify low-concentration substances in complex matrices. This is certainly one of the main advantages of coupling these techniques. In this perspective chapter, the advantages and limitations of the LC-MS system will be presented, sample preparation for this type of analysis and examples of applications that have had analytical success. It will also be mentioned the analytical advance in relation to miniaturization for lab-in-syringe, lab-on-valve, lab-on-a-chip, organ-on-a-chip, among others.