GC–MS CHARACTERIZATION AND FATTY ACID METHYL ESTER PROFILE OF BIODIESEL PRODUCED FROM GLIRICIDIA SEPIUM SEED OIL: IMPLICATIONS FOR FUEL QUALITY AND ENGINE APPLICATION

Abstract

Biodiesel consists primarily of fatty acid methyl esters (FAME) derived from renewable lipids. Understanding its molecular composition helps predict fuel behavior and feedstock influence. This study used gas chromatography–mass spectrometry (GC–MS) to characterize biodiesel produced from Gliricidia sepium seed oil using a snail–egg–periwinkle shell-derived CaO catalyst. The GC–MS analysis identified nine major chromatographic peaks between 7.608 and 10.011 minutes. Three compounds were confidently identified as FAMEs, comprising 28.68% of the total chromatographic area namely Methyl linoleate (18.26%) – Polyunsaturated, Methyl palmitate (5.83%) – Saturated and Methyl stearate (4.59%) – Saturated. Within this confirmed fraction, polyunsaturated FAMEs made up 63.67% and saturated FAMEs accounted for 36.33%; no monounsaturated FAMEs were confidently identified. Additionally, ethyl palmitate and ethyl stearate were detected as non-FAME ethyl esters.Two major peaks at 8.414 and 10.011 minutes (representing 18.19% and 33.83% area) remained tentative library matches due to ambiguous structures like 9,12-octadecadienoic acid and 1-cis-vaccenoylglycerol ethyl linoleate. They require authentic standards for confirmation. The high concentration of methyl linoleate improves low-temperature flow but increases oxidative degradation risks. Ultimately, GC–MS is highly useful for qualitative profiling, but uncalibrated peak areas must not be misinterpreted as total FAME content or conversion efficiency.