顶空气相色谱法测定生物柴油中的微量甲醇

建立了一种顶空气相色谱法测定生物柴油中微量甲醇的方法。确定了合适的顶空条件,即顶空进样器中试样温度70～80℃,平衡时间15～30 min。考察了不同类型色谱柱分离生物柴油中甲醇的情况。对于新制备的生物柴油,采用厚液膜非极性OV-1色谱柱或强极性CP-Wax色谱柱,可满足甲醇分离的要求;对于长久储存的生物柴油,采用强极性CP-Lowox色谱柱,甲醇可与其中的轻组分分离从而有效消除轻组分的干扰;CP-Lowox色谱柱还可用于B-5混合生物柴油中微量甲醇的测定。建立了采用CP-Lowox色谱柱外标法定量的标准曲线,相关系数大于0.999。测定甲醇的回收率为106%～124%,该方法具有较好的重复性,可满足一般分析的要求。

Determination of Methanol Content in Biodiesel by Headspace Gas Chromatography

A test method for the determination of methanol content in biodiesel by headspace gas chromatography was established.Suitable headspace conditions were confirmed,namely the sample temperature 70-80 ℃ and equilibrium time 15-30 min.Different kinds of columns were investigated for the separation of methanol from biodiesel.For fresh-made biodiesel samples,either nonpolar OV-1 column with thick film or column with polar phase such as CP-Wax column could achieve the separation well.For long-term stored samples,light components produced during the store would interfere in the determination of methanol,which could be eliminated by using CP-Lowox column.The methanol content in B-5 mixed biodiesel fuel could be determined by using CP-Lowox column also.An external standard quantitative formula was established with the correlation coefficient more than 0.999.Recoveries of the determination are in the range of 106%-124%.The repeatability of this method is good,which can meet the requirement of the routine analysis.