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1962年K.Porter和D.H.Volman提出转化法,将样品中的CO经镍触媒催化加氢转化成CH_4,用气相色谱仪氢火焰离子化检测器(FID)检测。目前这种方法已被广泛用来测定微量CO和CO_2,据报导,检测下限可达0.02ppm。在我们研制CO、CH_4标气的过程中,需对稀释气——高纯氮(99.999％)中存在的痕量CO、CO_2、CH_4进行定量测定。在高纯氮中,上述三个组分的含量一般都小于1ppm,因此要求分析仪器最低检出浓度应低于0.1ppm。北京分析仪器厂生产的SP-2307型气相色谱仪用H_2做载气,主要用于检测O_2、N_2、CO、CO_2、CH_4等气体,对CO等的最小检出浓度为1ppm,因而无法满足上述分析要求。为了适应高纯氮中痕量CO、CO_2和CH_4分析的需要,我们对仪器和操作方法作了一些改进,取得了较好的效果。改装后的气路系统见
In 1962 K.Porter and D.H.Volman proposed conversion method, the samples of CO catalytic nickel hydrogenation catalyst into CH_4, using gas chromatography hydrogen flame ionization detector (FID) detection. At present, this method has been widely used for the determination of trace CO and CO_2. According to the report, the detection limit is up to 0.02ppm. In the process of developing CO, CH_4 standard gas, we need to quantitatively determine trace amounts of CO, CO_2 and CH_4 in the diluent gas-high purity nitrogen (99.999%). In high-purity nitrogen, the above three components are generally less than 1ppm, thus requiring the minimum detection concentration of analytical instruments should be less than 0.1ppm. The SP-2307 gas chromatograph manufactured by Beijing Analytical Instrument Factory uses H 2 as a carrier gas and is mainly used for detecting gases such as O 2, N 2, CO, CO 2 and CH 4 and has a minimum detectable concentration of 1 ppm for CO and the like, thus failing to satisfy the above Analyze the requirements. In order to meet the needs of high-purity nitrogen trace CO, CO_2 and CH_4 analysis, we made some improvements to the instrument and operating methods, and achieved good results. Modified gas system see