气相色谱法-有效碳数定量测定环己烷及其烃类杂质含量

Quantitative determination of cyclohexane and hydrocarbon impurities therein by gas chromatography with effective carbon number

采用气相色谱法测定环己烷的纯度及烃类杂质含量,以有效碳数校正面积归一化法(简称有效碳数法)进行定量,研究了环己烷中难分离物质间二甲苯与对二甲苯的分离情况,杂质的最低检测限等,并与SH/T 1674—1999标准中的内标法定量结果进行对比。结果表明:使用带有氢火焰离子化检测器,聚甲基硅氧烷HP-1石英毛细管色谱柱(100 m×0.25 mm×0.50μm)的气相色谱仪,在柱箱起始温度32℃,保持12 min,然后以8℃/min的速率升至64℃,保持10 min,再以10℃/min的速率升至200℃,保持5 min,进样口温度230℃,检测器温度250℃,载气为氢气,进样量为1.0μL,分流比为1001的操作条件下,以有效碳数法定量,采用气相色谱法测定环己烷的纯度及烃类杂质含量,环己烷中难分离物质间二甲苯与对二甲苯能得到较好的分离;环己烷试样的纯度达99.96%;环己烷中杂质组分的最低检出限可达到1μg/g;方法的回收率为90.70%~108.62%,相对标准偏差小于3.0%;对于同一试样,有效碳数法和内标法的定量结果一致。

The purity of cyclohexane and the content of hydrocarbon impurities were determined by gas chromatography and were quantitatively analyzed by the effective carbon number correction area normalization method(short for effective carbon number method).The separation of m-xylene and p-xylene in cyclohexane and the minimum detection limit of impurities were studied and compared to the quantitative results of internal standard method according to standard SH/T 1674—1999.The results showed that the substances difficult to be separated from cyclohexane,m-xylene and p-xylene,can be well separated through effective carbon number quantification and gas chromatographic determination of cyclohexane and hydrocarbon impurities using a gas chromatograph with hydrogen flame ionization detector and polymethylsiloxane HP-1 quartz capillary column(100 m×0.25 mm×0.50μm)under the operating conditions of column temperature initially keeping at 32℃for 12 min,then heating to 64℃at a rate of 8℃/min and keeping for 10 min,and continuously heating to 200℃at a rate of 10℃/min and keeping for 5 min,injection port temperature 230℃,detector temperature 250℃,hydrogen as the carrier gas,injection volume 1.0μL and split ratio 1001;the purity of cyclohexane sample was 99.96%;the minimum detection limit of impurities in cyclohexane reached 1μg/g,the recovery rate 90.70%-108.62%and the relative standard deviation less than 3.0%;and for the same sample,the quantitative results of effective carbon number method were consistent with that of internal standard method.