建立应用电感耦合等离子体发射光谱(ICP-OES)法直接测定柴油中微量硫的分析方法。柴油样品经煤油简单稀释后直接进样分析,高浓度有机溶剂具有较高的饱和蒸气压,会造成等离子体的负载增加从而影响等离子体的稳定性,通过优化仪器的射频功率、载气流量和溶液提升量等工作参数维持了等离子体工作的稳定性,选用轴向观测技术提高了方法的灵敏度。硫的分析谱线处于紫外光区,光室中的氧气会吸收紫外光谱,采用氩气为保护气并延长氩气吹扫光路的时间控制了光室的纯度。采用在等离子体气体中通入一定量的氧气使高浓度有机碳完全燃烧,消除了碳沉积现象。详细地研究了硫的光谱干扰,采用实时背景扣除功能软件进行校正。通过加入内标元素Y校正了基体对硫信号抑制的差异,补偿了部分光谱漂移所带来的误差,有效地改善了测量的精密度。样品的分析结果表明,该方法硫的检出限为0.2μg·L^-1,三水平加标回收率在97.4%~101.8%之间,11次平行测定的相对标准偏差(RSD)在1.6%~2.1%之间。方法的样品前处理过程采用煤油稀释后直接测定,具有操作简单、快速、准确、线性范围广、检出限低和精密度好等特点,可用于柴油中微量硫的快速分析。
The method to detect trace sulphur content in diesel with inductively coupled plasma optical emission spectrometry(ICP-OES)was established.Kerosene sample was directly diluted,and then trace sulphur content in the solution was analyzed directly with ICP-OES.High concentrations of organic solvents with high saturation vapor pressure can cause the increasing of the loading of plasma,which would interfere the determination.In order to keep the working stability of equipment,operating parameters,such as RF power,loading gas velocity,were being optimized.First,the axially-viewed technology was adopted to increase the sensitivity of determination.Second,the analysis spectral lines of sulfur are located in ultraviolet area;therefore the Ar was adopted as protective air,and increase Ar clean time to keep the pure of sight source.Third,the condensation and deposition of high concentrations of carbon could be avoided effectively by introducing O_2 to plasma.Some detailed processes were used to further keep the stability of determinate signals such as:using element Y as internal standard to correct matrix effectives and compensate the errors caused by the spectral line shift,some automatic software were used to correct signal background.The results showed that the detection limits was 0.2μg·L~(-1),the relative standard deviation(RSD)was in range of 1.6%~2.1%,and the recovery of the methods was in range of 97.4% ~101.8%.The method has the following advantages:simple sample pretreatment,fast analyzing speed,low detection limitation,high precision and accuracy,as well as wide linear dynamic range.It can be used for rapid analysis of trace sulfur in diesel.