Quantitative analysis of free glycerol in biodiesel using solid-phase extraction and high-performance liquid chromatography

This study developed a method for separating and quantifying free glycerol in biodiesel. The free glycerol in biodiesel samples was separated using solid-phase extraction (SPE) and subsequently quantified by high-performance liquid chromatography (HPLC) using an ion-exchange stationary phase and refractive index detector (IR). The proposed method (SPE-HPLC-IR) was validated for high- and low-concentration samples (coefficient of determination, R-2 >= 0.99): limit of detection (0.00029% m/m, high; 0.00018% m/m, low); limit of quantification (0.00089% m/m, high; 0.00054% m/m, low); precision (standard deviation < 5.0%), and accuracy (recovery of 98.93% to 106.71%). The proposed method was compared with the reference method (ASTM D6584) using the paired t-test, and no statistical differences were found between them (95% confidence). As such, the proposed method offers a simple, quick, effective method for determining free glycerol in biodiesel and a viable alternative to the reference method.

Automated summary

The study developed a method for separating and quantifying free glycerol in biodiesel using SPE-HPLC-IR, which was validated for accuracy and precision, showing no statistical differences compared to the reference method. This proposed method offers a simple, quick, and effective alternative for determining free glycerol in biodiesel samples.