中心切割二维气相色谱法测定汽油中的甲缩醛含量

Determination of Methylal Content in Gasoline by Heart Cutting Two-Dimensional Gas Chromatography

采用微板流路控制（Deans Switch）中心切割技术,建立了分析汽油中甲缩醛含量的二维气相色谱法.该方法将两根不同极性色谱柱串联,汽油试样先经非极性DB-1毛细管色谱柱进行初步分离,通过优化设置中心切割时间,将汽油试样中的极性含氧化合物组分切换至强极性CP-LOWOX毛细管色谱柱进行进一步分离.以乙二醇二甲醚为内标物,可实现甲缩醛与汽油中常见的甲醇、乙醇等13种含氧化合物的完全分离.实验结果表明,甲缩醛含量（w）在0.01％～ 5.00％范围内时标准工作曲线呈良好的线性关系,线性相关系数达0.999 9,试样加标回收率为97.83％～ 104.11％,6次重复测定的相对标准偏差小于2.00％,甲缩醛检出限为0.003％（w）.该方法准确可靠,适合测定车用汽油中的甲缩醛含量.

A two dimensional gas chromatography for the determination of methylal in gasoline by capillary flow （Deans Switch） heart cutting technology was established with the series connection of nonpolar capillary column DB-1 and polar capillary column CP-LOWOX. A gasoline sample was separated firstly with the DB-1 column, and then by the optimized heart cutting, oxy-compounds in the sample were switched to the CP-LOWOX column for further separation. The Methylal and other 13 oxy-compounds （methanol, ethanol, etc.） could be separated and determined with 1, 2-dimethoxyethane as internal standard. The results showed that the calibration curve of methylal was linear in its concentration range of 0.01%-5.00% （w） with a correlation coefficient 0.999 9. The methylal recoveries in gasoline samples were in the range of 97.83%-104.11%, the relative standard deviations of six repeated determinations were less than 2.00%, and the detection limit of the methylal was 0.003% （w）.