高效液相色谱法测定咖啡因的不确定度评定

目的建立高效液相色谱法测定咖啡因的不确定度的评估方法。方法试样中的咖啡因用甲醇:水:磷酸=100:400:0.5(V:V:V)混合溶液进行提取,在波长280 nm下,经流动相洗脱,色谱系统分离,采用外标法测定咖啡因的含量,然后依据JJF 1059.1-2012《测量不确定度评定与表示》,对标准物质、仪器重复测量、精密度和样品称量等因素引入的不确定度进行分析和计算。结果当试样中咖啡因含量为7.50%时,在95%的置信区间下,其扩展不确定度为±0.13%(k=2)。实验过程中的不确定度主要来源于仪器测量、标准物质及人员操作。结论该不确定度评定适用于高效液相色谱法测定咖啡因含量的过程分析,对检测结果准确度的控制具有指导意义。

Evaluation of uncertainty in the determination of caffeine by high performance liquid chromatography

Objective To establish an evaluation method for the uncertainty in the determination of caffeine by high performance liquid chromatography. Methods The caffeine in the sample was extracted with methanol: water: phosphoric acid=100:400:0.5(V:V:V) mixed solution, eluted by mobile phase at the wavelength of 280 nm, separated by chromatographic system, and determined by external standard method. Then according to JJF 1059.1-2012 Evaluation and Expression of Measurement Uncertainty, the uncertainty of standard substance, instrument measurement, precision and sample weighing were introduced conduct analysis and calculation. Results When the caffeine content was 7.498%, the expanded uncertainty was ±0.13% (k=2) at 95% confidence interval. The uncertainty in the experiment mainly came from instrument measurement, reference material and personnel operating. Conclusion The uncertainty evaluation is applicable to the process analysis of caffeine content determination by high performance liquid chromatography, which has guiding significance for the control of the accuracy of the detection results.