Universidade Estadual Paulista, Campus de São José do Rio Preto Instituto de Biociências, Letras e Ciências Exatas R. Cristóvão Colombo, 2265, Jardim Nazareth São José do Rio Preto, SP, Brazil.
Universidade Estadual Paulista, Campus de São José do Rio Preto Instituto de Biociências, Letras e Ciências Exatas R. Cristóvão Colombo, 2265, Jardim Nazareth São José do Rio Preto, SP, Brazil.
Anal Chim Acta. 2019 Jun 20;1059:28-35. doi: 10.1016/j.aca.2019.02.002. Epub 2019 Feb 11.
The cumulative standard addition method allows the calibration of an instrument affected by matrix effects when a small sample volume is available. Recently, it was developed and validated a metrologically sound procedure to estimate the uncertainty of these measurements based on the modelling of the uncertainty of the extrapolation of the calibration curve by the linear least squares regression model. However, this procedure is only applicable when the uncertainty of cumulative sample dilutions and analyte mass additions are negligible given the uncertainty of the total solution volume (v) times the instrumental signal (I) (i.e. v∙I). This work developed a measurement uncertainty model, not limited by this assumption of the quality of calibrators preparation, based on Monte Carlo simulations. This method was successfully applied to the voltammetric measurements of uric acid in human serum, using a working nanocarbon electrode modified with Cu-nanocarbon-lignin, since the uncertainty model adapts to the uncertainty of cumulative volume additions. The validated procedure was checked through the analysis of spiked physiological serum samples and human serum samples, by assessing the metrological compatibility between estimated and reference values. The measurements are reported with an expanded uncertainty not larger than a target value of 0.56 mg dL. The used spreadsheet is made available as supplementary material.
累积标准加入法允许在可用小样品体积的情况下对受基质效应影响的仪器进行校准。最近，开发并验证了一种计量学上可靠的程序，该程序基于通过线性最小二乘回归模型对校准曲线外推的不确定性进行建模，从而估计这些测量的不确定度。然而，该程序仅适用于当累积样品稀释和分析物质量加入的不确定性相对于总溶液体积（v）与仪器信号（I）的乘积（即 v∙I）的不确定性可以忽略不计的情况。本工作基于蒙特卡罗模拟开发了一种测量不确定度模型，该模型不受校准剂制备质量的这一假设的限制。该方法成功应用于使用 Cu-纳米碳-木质素修饰的工作纳米碳电极对人血清中尿酸的伏安测量，因为不确定度模型适应于累积体积加入的不确定性。通过分析加标生理血清样品和人血清样品，通过评估估计值和参考值之间的计量兼容性，对验证后的程序进行了检查。测量结果报告的扩展不确定度不大于 0.56mg/dL 的目标值。所用的电子表格可作为补充材料提供。
