HPLC-ELSD法测定生物柴油中的游离甘油

摘要

采用液液萃取及高效液相色谱-蒸发光散射检测技术,建立了生物柴油中游离甘油含量的测定方法.待测生物柴油经乙腈-水(75:25)抽提并离心分离后,取部分下层水相进行分析.优化的色谱条件为:色谱柱Inertsil NH2 (250 nun ×4.6 mm,5μm );流动相为乙腈-水(75:25);流速1.0 mL/min;柱温35℃;进样量30 μL; ELSD载气压力360 kPa,漂移管温度28℃.结果表明,在优化条件下,生物柴油中游离甘油的含量在3.73-302.0 mg/kg范围内呈良好线性,相关系数r=0.999 8,检出限(S/N≥3)为2.1 mg/kg,其加标回收率为98%-101%,相对标准偏差(RSD)为0.59%-1.8%.方法灵敏、准确且重复性好,可为生物柴油中游离甘油含量的测定提供一种快速高效的方法.%An analytical method was established for the determination of free glycerol in biodiesel by using liquid - liquid extraction technique and high performance liquid chromatography( HPLC) with e-vaporative light-scattering detector ( ELSD). The biodiesel sample was extracted with acetonitrile -water(75 : 25) , followed by centrifugation. The obtained aqueous layer was analyzed by HPLC -ELSD. The testing conditions of HPLC - ELSD were optimized and the optimal conditions were as follows; separation column; Inertsil NH_2 column(250 mm ×4. 6 mm, 5 μm) , mobile phase; mixture of acetonitrile and water(75 : 25) , flow rate; 1.0 mL/min, injection volume; 30 μL, drift tube temperature; 28 ℃, gas pressure of nebulizer; 360 kPa. The result indicated that, under the optimal conditions, the calibration curve was linear over the content of free glycerol in biodiesel in the range of 3. 73 - 302. 0 nig/kg with a correlation coefficient of 0. 999 8, and the limits of detection( S/ N≥3)were 2. 1 mg/kg. The spiked recoveries were in the range of 98% -101% with relative standard deviations( RSDs) of 0.59% - 1.8%. The method was sensitive, accurate and reproducible, and could provide an efficient way for the determination of the content of free glycerol in biodiesel.