卡尔费休-气相色谱联用测定液态有机体系中的水分含量

Determination of Water Content in Liquid Organic System by Karl Fischer-Gas Chromatography Method

水分含量是评价有机体系的重要指标之一。有机体系中水分含量测定方法多种多样,不同有机体系需采用不同方法检测,无通用方法。采用卡尔费休法标定的甲醇水体系作外标物,建立了卡尔费休-气相色谱外标法测定含有醛、酮、醇、酸、酯、氧化剂、还原剂等有机体系产品中水分的普适性方法。该方法检出限(N/S=3)为0.0077%,定量限(N/S=10)为0.0232%。加标回收率为91.7%~100.8%,测定的相对偏差(n=9)均小于2%。该方法操作简单、快速、准确、环保,稳定可靠,重现性好,适用范围和检测范围广泛,检测范围可达0.02%~8%。

Moisture content is one of the important indicators for evaluating organic systems.There are various methods for measuring moisture content in organic systems.Different organic system needs to be detected by the corresponding methods,and there is no universal method.The Karl Fischer method has high measurement speed and high accuracy,but it has the significant disadvantages because it cannot be used to detect substances,such as aldehydes,ketones,oxidants,and reducants that can react with the KF reagent,and the KF reagent is expensive and toxic.The advantages of high separation efficiency of gas chromatography are used to overcome the shortcomings of the Karl Fischer method that cannot separate water from background compounds.Meanwhile,internal standard methods for gas chromatographic need stable and anhydrous internal standard substances.With the benzene-water mixed system as a standard,the external standard method for gas chromatography could be used to determine the moisture in the organic system,but its application is limited due to toxic benzene,which is harmful to health,and environmental-unfriendly.Based on the above statement,combining these two methods organically would expand the range of moisture measurement.A universal method for the determination of moisture in organic compounds has been established by the external standard method for gas chromatography with the methanol-water system calibrated by the Karl Fischer method as the external standard,which can be applied to determine the water content of organic compounds containing aldehydes,ketones,alcohols,acids,esters,oxidants,and reducing agents.The effects of chromatographic column type,inlet temperature,detector temperature,and chromatographic column heating program on the separation effect and detection sensitivity were studied.With the present method,the limits of detection(N/S=3)and quantification(N/S=10)are 0.0077%and 0.0232%,respectively.In the three systems of alcohol,ketone,and reaction mixture,the recovery tests of the added standard were carried out at three concentration levels of 80%,100%and 120%,respectively.The recovery rate varied 91.7%~100.8%,and the relative deviation of the determination(n=9)was less than 2%.The method is simple,fast,accurate and environmentally friendly with wide scope of application and detection.The detection results are stable and reproducible with the detection range of 0.02%~8%.