中红外光谱测定合成润滑油中胺类抗氧剂含量

Determination of Amino Antioxidant Content in Used Lubricating Oil Based on FTIR

为了监测在用合成航空润滑油抗氧剂消耗程度,采用合成基础油定量加绘制标准曲线的方法分析测定了润滑油中抗氧剂浓度。分析了润滑油的红外吸收光谱和抗氧剂仲胺基团的特征吸收峰,选择了3 320cm^(-1)与3 420cm^(-1)两点基线校正峰高建立标准曲线,其相关系数R^2=0.991 1。该方法的检出限低至0.003mol/L,定量限为0.009mol/L。用标准曲线对配制的样品和在用润滑油抗氧剂进行预测,其标准偏差分别为0.001 4和0.0023,与理论值和色谱法测定值接近;在用油的加标回收率在87.9%~94.3%之间,准确度较高。研究结果表明,通过建立标准曲线,中红外光谱可用于在用润滑油抗氧剂损耗的监测。

In order to monitor the loss of antioxidant in used lubricating oil,a standard curve was drawn to determine antioxidant content by means of adding sample in synthetic base oils.Spectral signature of secondary amine of antioxidant in infrared spectral region were analyzed,and corrected peak height against base line between 3 320cm-1 and 3 420cm-1 was selected to draw the standard curve,with correlation coefficient（R2）of 0.991 1,and detection limit of 0.003mol/L and quantification limit of 0.009mol/L.Some prepared samples were used to test the accuracy of standard curve,with a result close to the theoretical value with standard deviation（SD）of 0.0014.In-service Lubricating Oils were used to test the applicability of working curve with SD of 0.002 3,which shows that the results by using standard curve method were in agreement with those using chromatography.Values of recovery found with standard addition method in used lubricating oil were in range of 87.9%~94.3%.The study indicates that the method of FTIR combined with working curve can measure antioxidant content of in-service oil with accuracy.