Determination of Alkyl Esters Content by Gas Chromatography: Validation of Method Based on Short Column and Response Factor

In this study an analytical method, based on gas chromatography with flame ionization detection, using a short column and response factor (GCSCRF), was validated for the quantification of fatty acid alkyl esters (methylic or ethylic). During the validation process, the proposed method was employed to analyze twenty samples of fatty acid methyl esters and fatty acid ethyl esters. Biodiesel samples were produced from soybean oil and the validated method was found to be selective, being able to separate and identify every ester species present in the samples according to its carbon number. When the method was submitted to some variations in the sample preparation procedure, it remained robust. Limits of detection and quantification were 6.76 and 20.4 mg mL-1, respectively. The suggested method also showed great precision when successive analyses were carried out for different analysts, with standard deviation (SD) 0.6 for repeatibility and relative standard deviation (RSD) percentage 7.3% for intermediate precision, excellent accuracy when compared to other reference methods (EN 14103 and high-performance liquid chromatography with ultraviolet dection (HPLC-UV)) and recovery studies.

本研究建立了一种基于短柱-响应因子气相色谱-火焰离子化检测（GCSCRF）的分析方法，用于脂肪酸烷基酯（甲酯或乙酯）的定量分析，并完成了完整的方法学验证。方法学验证期间，采用该方法对20份脂肪酸甲酯与脂肪酸乙酯样品进行了分析。所用生物柴油样品均由大豆油制备得到，经验证该方法具备良好的选择性，可依据碳数分离并识别样品中所有酯类组分。当样品前处理流程存在小幅变动时，该方法仍保持优异的稳健性。该方法的检出限与定量限分别为6.76 mg·mL⁻¹与20.4 mg·mL⁻¹。此外，该方法展现出出色的精密度：由不同分析人员开展连续分析时，其重复性的标准偏差（SD）为0.6，中间精密度的相对标准偏差百分比为7.3%；与参考方法EN 14103及高效液相色谱-紫外检测法（HPLC-UV）的结果以及加标回收实验相比，该方法具备极佳的准确度。