气相色谱附双柱双氢火焰离子化检测器法同时测定环境空气中的总烃和非甲烷总烃

Simultaneous Determination of Total Hydrocarbon and Non-Methane Total Hydrocarbon in Ambient Air by Gas Chromatography with Double Columns and Double FIDs

建立一种气相色谱法配双柱双氢火焰离子化检测器(FID)同时测定环境空气中的总烃和非甲烷总烃含量的方法。全玻璃注射器中的样品(保存时间尽可能少于4h)通过连接两个定量环的十通阀直接进入气相色谱,分离总烃和甲烷的柱子均采用填充柱,载气均为氮气,流量分别为25,20mL·min^-1。根据气体在总烃柱和甲烷柱保留时间对总烃和甲烷进行定性,保留时间分别为0.120,0.404min;分别以扣除氧峰面积的总烃面积和甲烷峰面积对总烃和甲烷定量,再通过2者差值计算非甲烷总烃含量。结果表明:总烃与氮气、甲烷与氮气的物质的量之比均在0.5~10.0μmol·mol^-1内与其对应的色谱峰面积呈线性关系,总烃、甲烷、非甲烷总烃的检出限(3.143s)分别为0.025,0.031,0.031mg·m^-3(以甲烷计)。在3个浓度水平下进行回收试验,总烃和甲烷的回收率分别为99.8%~104%,99.7%~103%;测定值的相对标准偏差(n=6)分别为1.3%~5.6%,1.0%~5.1%。采用本方法对2个采样点位采集的样品中的总烃、甲烷含量进行了测定,计算出的非甲烷总烃质量浓度都小于1.0mg·m^-3,以这两个样品为基质进行加标回收试验,总烃和甲烷的回收率分别为102%~105%,107%~109%;测定值的相对标准偏差(n=5)分别为1.1%~1.7%,1.8%~1.9%。

A method for determination of the content of total hydrocarbon and non-methane total hydrocarbon in ambient air by gas chromatography with double columns and double FIDs was established.The samples in the glass syringe,with storage time as less than 4 has possible,was introduced into the gas chromatograph by the 10-valve with two quantitative rings.Total hydrocarbon and methane were separated by the 2 packed columns,and nitrogen was adopted as carrier with flow-rates of 25,20 mL·min-1,respectively.The qualitative analysis of total hydrocarbon and methane were made by retention time of gas sample passing through the total hydrocarbon column and methane column,with retention time of 0.120 min and 0.404 min,and the quantitative analysis was carried out based on total hydrocarbon peak area deducting the oxygen peak area and methane peak area respectively.It was shown by results that the mole ratios between total hydrocarbon and nitrogen and methane and nitrogen had a linear relationship in the range of 0.5-10.0μmol·mol-1 with their respective peak areas,with detection limits(3.143 s)of total hydrocarbon,methane and non-methane total hydrocarbon of 0.025,0.031,0.031 mg·m-3respectively.Test for recovery was made at 3 concentration levels,and results of recovery of total hydrocarbon and methane were ranged of 99.8%-104%and 99.7%-103%,with RSDs(n=6)in the range of 1.3%-5.6%and 1.0%-5.1%,respectively.The above method was used to determine the content of total hydrocarbon and methane in samples from two sampling points,and the determined values of non-methane total hydrocarbon were both lower than1.0 mg·m-3,giving values of recovery in the range of 102%-105%and 107%-109%,and RSDs(n=5)of the measured values found were ranged from 1.1%to 1.7%and 1.8%to 1.9%,respectively.