Conceição Valdomiro S, Saraiva Douglas P M, Denuault Guy, Bertotti Mauro
Department of Fundamental Chemistry, Institute of Chemistry, University of São Paulo-USP, São Paulo, 05508-000, Brazil.
School of Chemistry, University of Southampton, Highfield, Southampton SO17 1BJ, U.K.
Anal Chem. 2024 Sep 17;96(37):14766-14774. doi: 10.1021/acs.analchem.4c01645. Epub 2024 Sep 3.
Analytical methods are crucial for monitoring and assessing the concentration of important chemicals, and there is now a growing demand for methodologies that allow miniaturization, require lower sample volumes, and enable real-time analysis in the field. Most electroanalytical techniques depend on calibrations or standards, and this has several limitations, ranging from matrix interference, to stability problems, time required, cost and waste. Therefore, strategies that do not require standards or calibration curves greatly interest the analytical chemistry community. Here, we propose a new quantification method that does not rely on calibration and is only based on a single chronoamperometric curve recorded with a microelectrode. We show that satisfactory analytical information is obtained with just one chronoamperometric experiment that only takes a few seconds. We propose different data treatments to determine the unknown concentration, we consider the experimental conditions and instrument parameters, we report how parallel reactions affect the results, and we recommend procedures to implement the method in autonomous sensors. We also show that the concentration of several species can be derived if their ° values are sufficiently far apart or the sum of all concentrations if the ° values are too close. The proposed method was validated with a model redox system then further evaluated by determining ascorbic acid concentrations in standard solutions and food supplements, and paracetamol in a pain killer. The results for ascorbic acid were compared with those obtained by coulometry, and a good agreement was found, with a maximum deviation ca. 10.8%. The approach was also successfully applied to ascorbic acid quantification in solutions with different viscosity using ethylene glycol as a thickener.
分析方法对于监测和评估重要化学物质的浓度至关重要，目前对能够实现小型化、所需样品量更低且能在现场进行实时分析的方法的需求日益增长。大多数电分析技术依赖校准或标准品，这存在诸多局限性，从基质干扰到稳定性问题、所需时间、成本和废弃物等。因此，不需要标准品或校准曲线的策略引起了分析化学界的极大兴趣。在此，我们提出一种新的定量方法，该方法不依赖校准，仅基于用微电极记录的一条计时电流曲线。我们表明，仅通过一个只需几秒钟的计时电流实验就能获得令人满意的分析信息。我们提出不同的数据处理方法来确定未知浓度，考虑实验条件和仪器参数，报告平行反应如何影响结果，并推荐在自主传感器中实施该方法的程序。我们还表明，如果几种物质的°值相距足够远，则可以推导其浓度，或者如果°值太接近，则可以推导所有浓度的总和。所提出的方法用模型氧化还原系统进行了验证，然后通过测定标准溶液和食品补充剂中的抗坏血酸浓度以及止痛药中的对乙酰氨基酚进一步进行了评估。将抗坏血酸结果与库仑法获得的结果进行了比较，发现吻合良好，最大偏差约为10.8%。该方法还成功应用于以乙二醇作为增稠剂的不同粘度溶液中抗坏血酸的定量分析。
